Metrosensor electrodes Precision is not accidental, but brought about by design! 2 Table of contents Which electrode for which application? 6-7 Accessories 89-96 3 Electrodes for pH measurement 6 Accessories for Metrosensors 90-91 Electrodes for titration 7 Ion standards, buffer solutions, electrolytes 92-93 Electrical connections 94-96 Electrode catalog 8-87 dTrodes – Digital electrodes for OMNIS 8-9 How is a Metrosensor made? 97-98 iTrodes – Intelligent electrodes for the Titrando generation 10 Theoretical fundamentals 99-120 Unitrode and Solvotrode easy Clean – 1. Fundamentals of potentiometry 99-114 Cleaning at the touch of a button 11 1.1. Electrode construction 99 Separate pH glass electrodes 14-15 1.2. From the measured potential to Electrodes for pH measurement 16-19 the ion concentration 99-100 Electrodes for pH titration 20-23 1.3. Measuring electrodes 101-109 Special electrodes for pH measurement/pH titration 24-27 1.3.1. pH glass electrodes 101-105 Electrodes for pH titration in 1.3.2. Metal electrodes 105-107 HF-containing solutions 28-29 1.3.3. Ion-selective electrodes 107-109 Separate metal electrodes 32-33 1.4. Reference electrodes 109-114 Titrodes – the maintenance-free metal electrodes 34-35 1.4.1. Silver/silver chloride reference electrode 109 Combined metal electrodes 36-37 1.4.2. Metrosensor «Long Life» reference system 110 Electrodes for Karl Fischer titration 38-39 1.4.3. Diaphragms 110-113 Ion-selective electrodes and accessories 42-45 1.4.4. Reference electrolytes and Electrodes for surfactant titration and accessories 46-49 bridge electrolytes 114 Reference electrodes 52-55 2. Fundamentals of conductometry 115-119 Working electrodes for trace analysis and CVS 58-59 2.1. General 115-118 Reference and auxiliary electrodes for 2.2. Conductivity measurement in accordance trace analysis and CVS 60-61 with USP and Pharm. Europe (EP) 118-119 Electrodes for Metrohm Autolab RDE and RRDE 62-63 3. Temperature measurement 120 Microelectrodes 64-65 Electrodes for the electrochemical quartz Appendix 122-133 crystal microbalance 66-67 Technical specifications 122-133 Screen-printed electrodes 68-69 Interdigitated electrodes/microelectrodes 70 Conductivity measuring cells for 912/914 meters 74-75 Conductivity measuring cells for 856 Conductivity Module 76-77 Conductivity measuring cells 78-79 Sensors for stability measurement 80-81 Temperature sensors 82-83 Sensors for thermometric titration 84-85 Sensor for photometry 86-87 4 Metrohm has long-standing experience in ion analysis – why should you wrack your brains, when we've already done the thinking for you? Metrohm Application Bulletins – instructions that are guaranteed to work. • Pharm PAC – the most important methods for the Metrohm PACs (Potentiometric Analysis Collections) determination of pharmaceutical ingredients in contain ready-to-use methods, which are right up to accord ance with European and US pharmacopeias. date and always in compliance with the respective standards and regulations. • Wine PAC – the most important methods in wine analysis. • Surf PAC – the most important methods in surfactant analysis. • Plate PAC – the most important methods for the analysis of galvanic baths. • Oil PAC – the most important methods for the analysis of petroleum products. • Food PAC – the most important methods in food analysis. You can fi nd the applications listed here as well as others in the Application Finder at: www.metrohm.com/Applications Get your know-how from the market leader! www.metrohm.com Electrode catalog The illustrations of the articles are, unless specified other-Materials abbreviations: 5 wise, approximately in original size. EP Epoxide EVA Ethylenvinylacetate Unless otherwise specified, all combined pH electrodes PBT Polybutylenterephthalate are filled with the referenced electrolytes c(KCl) = 3 mol/L PCTFE Polychlortrifluoroethylene (Order number 6.2308.020). PE Polyethylene PEEK Polyetheretherketone The abbreviation «LL reference system» stands for the PMMA Polymethyl metacrylate Metrosensor «Long Life» reference system. More detailed POM Polyoxymethylene information on this can be found in the theoretical PP Polypropylene section, Chapter 1.4.2. PPO Polyphenylenoxide PTFE Polytetrafluoroethylene «DJ» stands for «double junction». These electrodes are PVC Polyvinyl chloride equipped with a bridge electrolyte chamber; the bridge electrolyte is replaceable, which means that it can be adapted to suit the sample. Detailed information concerning technical specifications can be found in the appendix «Technical Specifications.» The electrochemical parameters are specified for 25 °C, the outflow rates with a hydrostatic pressure of a 10 cm high water column. «Shaft length» refers to the length of the electrode tip up to the lower edge of the electrode plug-in head. The installation length is the length from the electrode tip to the upper edge of the standard ground-joint. In the case of flexible SGJ sleeves, this corresponds to the length down to the electrolyte refill opening below. All flexible SGJ sleeves have like their size the standard ground-joint 14/15. Electrodes for pH measurement 6 Application Details Electrode Order number Page Universal Clear, aqueous solutions, pH 0...14 Primatrode with NTC 6.0228.010 16 Universal laboratory use, pH 0...14 Unitrode easyClean with Pt1000 6.0260.010 18 Routine measurement in similar samples Ecotrode Gel with NTC 6.0221.600 16 pH 1...11 Water General (demineralized water, drinking Aquatrode Plus with Pt1000 6.0257.600 18 water, process water, sea water, environ- mental sector) Waste water General Unitrode easyClean with Pt1000 6.0260.010 18 Sewage containing sulfides Profitrodex 6.0255.100 20 Soil samples General (aqueous suspensions) Flat-membrane electrodex 6.0256.100 24 Agriculture Fertilizers Unitrode with Pt1000 6.0258.600 18 Horticulture solutions containing proteins Porotrodex 6.0235.200 24 Plant cultivation Liquid manure Profitrodex 6.0255.100 20 Small sample volumes, culture media Biotrodex 6.0224.100 24 Nutrient solutions Viscotrodex 6.0239.100 26 Food General Unitrode with Pt1000 6.0258.600 18 Beverages Food containing proteins, beer Porotrodex 6.0235.200 24 Semi-luxury Bread, meat, cheese, dough (measurements Spearhead electrode with Pt1000 6.00226.600 24 articles semi-solid samples) Fruit and vegetable juices, wine, spirits Unitrode easyClean with Pt1000 6.0260.010 18 Drinking water Aquatrode Plus with Pt1000 6.0257.600 18 Pharmaceuticals Creams, liquid formulations, medicinal Viscotrodex 6.0239.100 26 Biological syrup, mouthwash solutions, raw materials samples monitoring in accordance with pharmacopoeias Dialysis solutions, urine Unitrode easyClean with Pt1000 6.0260.010 18 Solutions containing proteins Porotrodex 6.0235.200 24 Infusion solutions Aquatrode Plus with Pt1000 6.0257.600 18 Small sample volumes, gastric juice, serum Biotrodex 6.0224.100 24 Pilot plant measurements Syntrode with Pt1000 6.0248.600 26 Cosmetics General (emulsions, shampoos, shower Viscotrodex 6.0239.100 26 baths, liquid soaps, lotions, mouthwashes, perfumes) Skin (surfaces) Flat-membrane electrodex 6.0256.100 24 Make-up Microelectrodex 6.0234.100 26 Cleaning agents General (detergents, dishwashing liquids, Viscotrodex 6.0239.100 26 Detergents cleaning agents, surfactant solutions) Samples with pH values > 10 Profitrodex 6.0255.100 20 High-viscosity samples Unitrode with Pt1000 6.0258.600 18 Leather Bleaching and dyeing baths, tanning liquors Profitrodex 6.0255.100 20 Paper Fountain solution for offset printing, glue Unitrode easyClean with Pt1000 6.0260.010 18 Textiles Leather, paper, textiles (surface) Flat-membrane electrodex 6.0256.100 24 Washing liquors Viscotrodex 6.0239.100 26 Paints Stains (wood), dye baths, inks Profitrodex 6.0255.100 20 Lacquers Dispersions, emulsions, resins, lacquers, Unitrode easyClean with Pt1000 6.0260.010 18 Solvents suspensions Paint coatings (surfaces) Flat-membrane electrodex 6.0256.100 24 Non-aqueous, polar solvents EtOH-Trodex 6.0269.100 18 Electroplating General (etching, pickling and degreasing baths, Profitrodex 6.0255.100 20 Metal process- alkaline electroplating and phosphatizing baths) ing Acidic electroplating baths Unitrode with Pt1000 6.0258.600 18 Drilling oil emulsions Viscotrodex 6.0239.100 26 Special Measurements in semi-solid samples Spearhead electrode with Pt1000 6.00226.600 24 applications Solutions containing proteins Porotrodex 6.0235.200 24 Samples with pH values > 12 and Unitrode with Pt1000 6.0258.600 18 temperatures 50...80 °C Temperature 80...100 °C Unitrode with Pt1000 reference 6.0258.600 18 electrolyte: Idrolyte Ion-deficient, weakly buffered solutions Aquatrode Plus with Pt1000 6.0257.600 18 Small sample volumes Biotrodex 6.0224.100 24 Flat-membrane electrodex 6.0256.100 24 Surface measurements Flat-membrane electrodex 6.0256.100 24 Developer baths, concentrated acids Profitrodex 6.0255.100 20 Emulsions/suspensions Unitrode easyClean with Pt1000 6.0260.010 18 Fuels containing ethanol/E85 EtOH-Trodex 6.0269.100 18 x It is recommended to use an external temperature sensor (e.g. 6.1114.010 or 6.1110.100) Electrodes for titration Application Details Electrode Order number Page 7 Aqueous General Ecotrode Plus 6.0262.100 20 acid/base Routine measurement in similar samples Ecotrode Gel 6.0221.100 20 titrations Alkaline samples, Bayer liquors Unitrode 6.0259.100 20 Titrations at high temperatures Unitrode with reference electro- 6.0259.100 20 lyte: Idrolyte Acid content of alcoholic beverages Unitrode easyClean with Pt1000 6.0260.010 18 Titrations with small sample volumes Microelectrode 6.0234.100 26 Flat-membrane electrode 6.0256.100 24 Titrations in ion-deficient aqueous media Aquatrode Plus 6.0253.100 22 Carbonate hardness and acid capacity of Aquatrode Plus with Pt1000 6.0257.600 18 water, p & m values Electroplating, etching and phosphatizing baths Profitrode 6.0255.100 20 Etching baths containing fluoride or hydro- Solitrode HF 6.0223.100 28 fluoric acid Combined antimony electrode 6.0421.100 28 Samples containing protein Porotrode 6.0235.200 24 Nonaqueous Titrations with perchloric acid, cyclohexylamine, Solvotrode easyClean with 6.0229.010 22 acid/base alcoholic HCl, determination of base number c(LiCl) = 2 mol/L in ethanol titrations (TBN) of crude oil products Titrations with alcoholic KOH, NaOH and Solvotrode easyClean with 6.0229.010 22 TBAOH, potassium methylate, determination c(TEABr) = 0.4 mol/L in ethylene of the total acid number (TAN) of petroleum glycol products, free fatty acid/hydroxyl number in oils and fats Redox titrations Titrations without change of the pH value Pt-Titrode 6.0431.100 34 Titrants: Titrations with change of the pH value Combined Pt-ring electrode 6.0451.100 36 arsenite, cersulfate Chemical oxygen demand (COD) in waters Combined Au-ring electrode 6.0452.100 36 iron(III), iodine, potassium bromate Penicillin, ampicillin Combined Au-ring electrode 6.0452.100 36 sodium nitrite Bromatometry, iodometry and cerimetry in Pt-Titrode 6.0431.100 34 oxalic acid, perman- accordance with Pharm. Europe & USP ganate, thiosul- Titrations in Ipol mode Double Pt-sheet electrode 6.0309.100 32 fate, titanium(III), Double Au-ring electrode 6.00353.100 32 Hg(NO3)2 Karl Fischer Water determination according to Karl Double Pt-wire electrode 6.0338.100 38 titrations Fischer Precipitation Chloride in general, sodium chloride content Ag-Titrode 6.00430.100 34 titrations in foods Titrants: Chloride in dialysis and infusion solutions Ag-Titrode with Ag2S coating 6.00430.100S 34 Silver nitrate Titrations in accordance with Pharm. Europe & USP Ag-Titrode with Ag2S coating 6.00430.100S 34 Determination of hydrogen sulfide, Ag-Titrode with Ag2S coating 6.00430.100S 34 mercaptans, carbonyl sulfides, sulfides Chloride, bromide, iodide and cyanide in Ag-Titrode with Ag2S coating 6.00430.100S 34 electroplating baths Fluoride/hydrofluoric acid in etching baths F–-ISE – crystal membrane 6.0502.150 42 Complexometry Back titration of excess Ba2+ with EDTA Combined Ca2+-ISE polymer 6.0510.100 42 Titrants: membrane EDTA, Determination of Ca2+, Mg2+ in aqueous Combined Ca2+-ISE polymer 6.0510.100 42 Complexon© solutions (in accordance with AB 125) membrane 42 III and IV Determination of Al, Ba, Bi, Ca, Cd, Co, Fe, Cu2+-ISE crystal membrane 6.0502.140 42 Mg, Ni, Pb, Zn Photometric Titrations in aqueous and nonaqueous Optrode 6.1115.000 86 titrations solutions Surfactants in Titration of anionic and cationic surfactants, Surfactrode Resistant 6.0507.130 46 nonaqueous titrations in chloroform, formulations con- media taining oil such as cooling lubricants, drilling Aromatic and and cutting oils, oil-containing shower baths, aliphatic hydro- pH < 10 carbons, ketones, Titration of anionic and cationic Surfactrode Refill 6.0507.140 46 gasoline, kerosene, surfactants, titration of surfactant formula-dichloroethane and tions, washing powders, soaps, pH > 10 trichloroethane Surfactants in Titration of cationic surfactants «Cationic Surfactant» electrode 6.0507.150 46 aqueous media Titration of anionic surfactants «Ionic Surfactant» electrode 6.0507.120 46 Titration of non-ionic surfactants NIO electrode 6.0507.010 46 Titration of pharmaceutical ingredients with sodium tetraphenylborate dTrodes – Digital electrodes for OMNIS 8 dTrodes – simply easier The latest generation of intelligent, digital electrodes – the dTrodes – were specifically developed for the OMNIS platform. The dTrodes combine the measuring electrode and the measuring amplifier in one slim and robust sensor. The electrode head contains an analog-to-digital con- verter, which converts the measured analog signal into a binary code. The digital data is then optically transmitted to the titrator. This means, the sensor is electrostatically decoupled from the titrator. The signal is thus not affected by electrostatic interferences and is therefore of low noise. Important sensor data, such as article and serial numbers, calibration data, calibration history, working life, and calibration validity period are automatically saved on the integrated memory chip. Therefore, the sensor can easily be used on another instrument without having to repeat the calibration. This also eliminates the danger of mixing up sensors. LED for sensor status When connecting a dTrode to the OMNIS titrator, the sensor is automatically recognized by the software and saved in its sensor list. Immediately, all sensor data is transferred to the software and checked for its validity. A problem with the sensor, e.g., an invalid parameter, can be recognized immediately by the color of the integrated LED. Sensor management at its best! Ordering information dUnitrode with Pt1000 6.00200.300 dEcotrode plus 6.00201.300 dAquatrode plus with Pt1000 6.00202.300 dSolvotrode 6.00203.300 dProfitrode 6.00204.300 dAg-Titrode 6.00404.300 dAg-Titrode with Ag2S coating 6.00404.300S dPt-Titrode 6.00401.300 dAg ring electrode 6.00402.300 dPt ring electrode 6.00403.300 dCalcium-ISE, combined 6.00502.300 Digital measuring module 6.02100.010 6.00502.300 6.00402.300 6.00204.300 9 6.00404.300 6.02100.010 iTrodes – Intelligent electrodes for the Titrando generation 10 Easy digital identification The iTrodes contain a memory chip which enables the storage of all relevant sensor data, such as article and serial number, calibration data, calibration history, working live and calibration validity period. All of the sensor data are uploaded automatically when the iTrode is connected to an instrument. This means, that the possibility of any mix-up or editing error is eliminated and each analysis result is traceable to the used electrode. Digital data transmission When connected to the sensor, the analog/digital con- verter in the 854 iConnect (2.854.0010) converts the analog measuring signal into binary code. Digital data transmission means that the measuring signal is no longer susceptible to electrostatic influences. Interference-free transmission can now be guaranteed, no matter how long the electrode cable is. iTrodes can be used with the 913 and 914 pH meter, the 916 Ti-Touch or the 888 and 90x Titrandos. Ordering information iAquatrode Plus with Pt1000 6.0277.300 iUnitrode with Pt1000 6.0278.300 iSolvotrode 6.0279.300 iEcotrode Plus 6.0280.300 iAg-Titrode 6.00470.300 iAg-Titrode with Ag2S coating 6.00470.300S iPt-Titrode 6.0471.300 iAg-ring electrode, combined 6.00450.300 iPt-ring electrode, combined 6.0451.300 iConnect 2.854.0010 Unitrode and Solvotrode easy Clean – Cleaning at the touch of a button Easy cleaning of the diaphragm: Just press once on the 11 electrode head and the electrolyte flows out. The diaphragm does not need to be touched any more for cleaning. Highlights • Easy contact-free cleaning of the diaphragm • Greater accuracy and reproducibility of the electrolyte flow (glass on glass, the spring in the head returns to the defined starting point) • Reduced immersion depth of the sensor through optimization of the membrane shape Ordering information Unitrode easy Clean with Pt1000, fixed cable, plug F 6.0260.010 Unitrode easy Clean with Pt1000, fixed cable 2 m, plug F 6.0260.020 Solvotrode easy Clean, fixed cable, plug F 6.0229.010 Solvotrode easy Clean, fixed cable 2 m, plug F 6.0229.020 12 Electrodes for pH measurement/pH titration 13 Fine-tune your measurements! The greatest precision and ease of care – these are the two outstanding properties of Unitrode and Aquatrode Plus. The constant electrolyte outflow of the fixed ground-joint diaphragm (which is largely insensitive to contamination) guarantees a low-noise measuring signal, even in difficult samples and independent of the measuring conditions. Further details can be found in the theoretical section on page 111. Separate pH glass electrodes 14 Separate pH glass electrode Technical specifications • Electrically shielded pH range 0...14 • Blue T glass for reliable results, e.g. in differential Temperature range 0...80 °C potentiometry in non-aqueous media Installation length 142 mm • Optimal length for sample changer applications Shaft diameter 12 mm Minimum immersion depth 15 mm Electrode plug-in head Metrohm plug-in head G Differential potentiometry In addition to the measuring electrode, a reference electrode and an auxiliary electrode are required for differential potentiometry. The shielding of the reference electrode must be identical to that of the measuring electrode. Reference electrodes for differential potentiometry (see «Reference electrodes» section) • Ag/AgCl DJ reference electrode, length 100 mm, Metrohm plug-in head G Without electrolyte filling, without cable 6.0729.100 • Ag/AgCl DJ reference electrode, length 138 mm, Metrohm plug-in head G Without electrolyte filling, without cable 6.0729.110 Auxiliary electrodes for differential potentiometry, Metrohm plug-in head B (see «Separate metal electrodes» section) Separate Pt wire electrode 6.0301.100 Separate Pt rod electrode 6.1241.040 + 6.1248.000 Separate Pt ring electrode 6.0351.100 15 Ordering information Separate pH glass electrode, without cable 6.0150.100 Electrodes for pH measurement 16 Primatrode with NTC – the economical entry to Technical specifications GLP-compliant pH measurement Primatrode • For solutions that do not contain precipitates, pro-Shaft material PP teins or sulfides pH range 0...14 • Long-lasting standard electrode Temperature range 0...80 °C • Unbreakable plastic shaft Temperature sensor NTC • Impact protection for the glass membrane Diaphragm Ceramic pin • LL reference system with long-term stability Installation length 113 mm • Variant 6.0228.020 with waterproof plug I for use Shaft diameter 12 mm with the 913/914 pH meter (IP67)) Minimum immersion depth 15 mm Solitrode with Pt1000 – robust and reliable, ideal Technical specifications for routine laboratory use Solitrode • For solutions that do not contain precipitates, proteins Shaft material PP or sulfides pH range 0...14 • Long-lasting standard electrode Temperature range 0...80 °C • Unbrekable plastic shaft Temperature sensor Pt1000 • Impact protection for the glass membrane Diaphragm Ceramic pin • LL reference system with long-term stability Installation length 113 mm Shaft diameter 12 mm Minimum immersion depth 15 mm Ecotrode Gel – the maintenance-free solution Technical specifications • Ideal for routine measurements in similar samples Ecotrode Gel • Specialist for measurement in polymer dispersions Shaft material Glass (water-based dispersion paints and adhesive pH range 1...11 dispersions on basis of acrylic acid esters and Temperature range 0...60 °C styrene; butyl acrylates) Temperature sensor NTC • Maintenance-free Diaphragm Twin pore • Lifetime indicator Installation length 125 mm • LL reference system with long-term stability Shaft diameter 12 mm Minimum immersion depth 20 mm Electrode plug-in head Metrohm plug-in head U How to store your electrodes correctly: Rapid response is not a matter of magic, but rather a question of storage! Metrohm recommends the patented storage solution (6.2323.000) for all combined pH glass electrodes which use c(KCl) = 3 mol/L as the reference electrolyte. This prevents the aging of the glass membrane and, as a result, guarantees response times short as they were on the first day. More information on this can be found in the theoretical section in Chapter 1.3.1. «pH glass electrodes.» 17 Primatrode The economical entry to GLP-compliant pH measurement Solitrode Robust and reliable, ideal for routine laboratory use Ecotrode Gel The maintenance-free solution Ordering information Primatrode with NTC, fixed cable (1.2 m) with plug F + 1 x B (2 mm) 6.0228.010 Primatrode with NTC, fixed cable (1.2 m) with plug I (IP67) + 1 x B (2 mm) 6.0228.020 Solitrode with Pt1000, without cable, plug-in head U 6.0228.600 Solitrode without temperature sensor, without cable 6.0220.100 Ecotrode Gel with NTC, without cable, plug-in head U 6.0221.600 Ecotrode Gel without temperature sensor, without cable 6.0221.100 Electrodes for pH measurement 18 Unitrode with Pt1000 – high performance in Technical specifications difficult samples and at high pH values Unitrode • For universal use, even in dyes, pigments, inks, suspen-Shaft material Glass sions, resins and polymers pH range 0...14 • Fixed ground-joint diaphragm insensitive to contamination Temperature range 0...100 °C • High temperature resistance and very low alkali error Temperature sensor Pt1000 • Rapid response to temperature changes Diaphragm Fixed ground-joint • Outer electrolyte Idrolyte for temperatures of Installation length 125 mm 80...100 °C Shaft diameter 12 mm • LL reference system with long-term stability Minimum immersion depth 25 mm Aquatrode Plus with Pt1000 – ideal for weekly Technical specifications buffered aqueous solutions Aquatrode Plus • Special electrode membrane glass: precise measuring Shaft material Glass values and very rapid response times, even in weekly pH range 0...13 buffered solutions such as drinking water, surface Temperature range 0...60 °C water and rain water and other poorly conducting Temperature sensor Pt1000 solutions Diaphragm Fixed ground-joint • Maintenance-free inner reference electrolyte (gel) Installation length 135 mm • Variable bridge electrolyte for special applications Shaft diameter 12 mm • Fixed ground-joint diaphragm insensitive to contamination Minimum immersion depth 20 mm • Optimized length for sample changer applications • LL reference system with long-term stability EtOH-Trode – the specialist for ethanol Technical specifications • Developed for pHe measurement in ethanol EtOH-Trode • Special membrane glass Shaft material Glass • Very precise ground-joint diaphragm pH range 0...13 • Double-junction system for free choice of electrolytes Temperature range 0...80 °C (e.g. 3 M KCI in ASTM D 6423, 1 M LiCI in EN Diaphragm Fixed ground-joint 15490). Installation length 125 mm • LL reference system with long-term stability Shaft diameter 12 mm Minimum immersion depth 20 mm Electrode plug-in head Metrohm plug-in head G Wellness for the electrode Reliable measuring results over long periods of time can only be guaranteed if the glass membrane and the diaphragm receive preventative and regular care. Cleaning by means of etching with toxic chemicals or a mechanical treatment of the diaphragm is not only complicated and expensive, it also accelerates the aging of the pH glass electrode as well. The care kit (6.2325.000, pg. 92) was developed for simple, gentle cleaning of pH glass electrodes with a liquid electrolyte. Regular application can considerably prolong its lifetime. 19 EtOH-Trode The specialist for pHe measurement Unitrode High performance, even in difficult samples and at high temperatures Aquatrode Plus Rapid response times and greatest precision in poorly buffered solutions due to special electrode glass and fixed ground-joint diaphragm Ordering information Unitrode easyClean with Pt1000, fixed cable (1.2 m) plug F + 1 x B (2mm) 6.0260.010 Unitrode easyClean with Pt1000, fixed cable (2 m) plug F + 1 x B (2 mm) 6.0260.020 Unitrode without temperature sensor, without cable 6.0259.100 Unitrode with Pt1000, without cable, plug-in head U 6.0258.600 iUnitrode with Pt1000 6.0278.3001 dUnitrode with Pt1000 6.00200.3002 Aquatrode Plus with Pt1000, without cable, plug-in head U 6.0257.600 Aquatrode Plus without temperature sensor, without cable 6.0253.100 iAquatrode Plus with Pt1000 6.0277.3001 dAquatrode Plus with Pt1000 6.00202.3002 EtOH-Trode without temperature sensor, without cable 6.0269.100 1 Further information about iTrodes can be found on pg. 10. 2 Further information about dTrodes can be found on pg. 8. Electrodes for pH titration 20 Ecotrode Gel – the maintenance-free solution Technical specifications • Ideal for routine measurements in similar samples Ecotrode Gel • Maintenance-free Shaft material Glass • Lifetime indicator pH range 1...11 • LL reference system with long-term stability Temperature range 0...60 °C Diaphragm Twin pore Installation length 125 mm Shaft diameter 12 mm Minimum immersion depth 20 mm Electrode plug-in head Metrohm plug-in head G Ecotrode Plus – high durability in routine use at a Technical specifications fair price Ecotrode Plus • For acid/base titrations in various kinds of solutions Shaft material Glass • Fixed ground-joint diaphragm insensitive to contamination pH range 0...13 • Ideal for routine laboratory use Temperature range 0...80 °C • LL reference system with long-term stability Diaphragm Fixed ground-joint Installation length 125 mm Shaft diameter 12 mm Minimum immersion depth 20 mm Electrode plug-in head Metrohm plug-in head G Profitrode – professional working in the most Technical specifications difficult of matrices Profitrode • For difficult matrices (galvanic baths, precipitates, Shaft material Glass samples containing sulfides, etc.) pH range 0...14 • Flexible ground-joint diaphragm, particularly easy to Temperature range 0...80 °C clean Diaphragm Flexible ground-joint • Double-junction construction Installation length 113/170/310 mm • Available in various lengths Shaft diameter 12 mm (113/170/310 mm) Minimum immersion depth 30 mm • LL reference system with long-term stability Electrode plug-in head Metrohm plug-in head G Unitrode – high performance in difficult samples Technical specifications and at high pH values Unitrode • For universal use, even in dyes, pigments, inks, sus-Shaft material Glass pensions, resins and polymers pH range 0...14 • Fixed ground-joint diaphragm insensitive to contamination Temperature range 0...100 °C • High temperature resistance and very low alkali error Diaphragm Fixed ground-joint • Rapid response to temperature changes Installation length 125 mm • Outer electrolyte Idrolyte for temperatures of Shaft diameter 12 mm 80...100 °C Minimum immersion depth 25 mm • LL reference system with long-term stability 21 Ecotrode Gel Maintenance-free Routine Ecotrode Plus High durability in routine use at a fair price Profitrode Professional working in the most difficult matrices Unitrode High performance in difficult samples and at high pH values Ordering information Ecotrode Gel without temperature sensor, without cable 6.0221.100 Ecotrode Plus, without temperature sensor, without cable 6.0262.100 iEcotrode Plus without temperature sensor 6.0280.3001 dEcotrode Plus, without temperature sensor 6.00201.3002 Profitrode, length 113 mm, without cable 6.0255.100 Profitrode, length 170 mm, without cable 6.0255.110 Profitrode, length 310 mm, without cable 6.0255.120 dProfitrode, without temperature sensor 6.00204.3002 Unitrode easyClean with Pt1000, fixed cable (1.2 m) plug F + 1 x B (2 mm) 6.0260.010 Unitrode easyClean with Pt1000, fixed cable (2 m) plug F + 1 x B (2 mm) 6.0260.020 Unitrode without temperature sensor, without cable 6.0259.100 Unitrode with Pt1000, without cable, plug-in head U 6.0258.600 iUnitrode with Pt1000 6.0278.3001 dUnitrode with Pt1000 6.00200.3002 1 Further information about iTrodes can be found on pg. 10. 2 Further information about dTrodes can be found on pg. 8. Electrodes for pH titration 22 Aquatrode Plus – ideal for aqueous, weekly Technical specifications buffered solutions Aquatrode Plus • Precise measuring values and very rapid response Shaft material Glass times in ion-deficient or weekly buffered solutions – pH range 0...13 such as drinking water, surface water and rain water Temperature range 0...60 °C – thanks to special membrane glass and optimized, Diaphragm Fixed ground-joint fixed ground-joint diaphragm insensitive to contamination Installation length 135 mm • Maintenance-free inner reference electrolyte (gel) Shaft diameter 12 mm • Variable bridge electrolyte for special applications Minimum immersion depth 20 mm • LL reference system with long-term stability Electrode plug-in head Metrohm plug-in head G Solvotrode easyClean – space-saving alternative for titration in non-aqueous media Technical specifications • For non-aqueous titrations in the pharmaceutical sector Solvotrode easyClean • For determination of TAN/TBN in compliance with Shaft material Glass ASTM D4739, D2896 and D664 and DIN ISO 3771 pH range 0...14 and DIN EN 12634 Temperature range 0...70 °C • Reference electrolyte: LiCl(sat) in ethanol Diaphragm Flexible ground-joint • Rapid response and stable measuring values in Installation length 125 mm organic solvents Shaft diameter 12 mm • Shielding against electrostatic effects Minimum immersion depth 20 mm • EasyClean diaphragm, particularly easy and contactless cleaning • LL reference system with long-term stability Drinking water analysis – Does it matter at which stirring rate titration is performed? When stirring in ion-deficient solutions, streaming potentials occur at pH electrodes with ceramic pin diaphragms which falsify measuring values. In the case of a SET titration, e.g. to a defined pH value, a considerable error can be produced if an incorrect value is measured at the start or at the endpoint of the titration. See page 111 to find out why you can forget about this problem when using the Aquatrode Plus. 23 Solvotrode easyClean Space-saving alternative for titration in non-aqueous media Aquatrode Plus Fast response and excellent pre- cision in weekly buffered solu- tions thanks to special membrane glass and fixed ground-joint diaphragm Ordering information Aquatrode Plus without temperature sensor, without cable 6.0253.100 Aquatrode Plus with Pt1000, without cable, plug-in head U 6.0257.600 iAquatrode Plus with Pt1000 6.0277.3001 dAquatrode Plus with Pt1000 6.00202.3002 Solvotrode easyClean, fixed cable (1.2 m) plug F 6.0229.010 Solvotrode easyClean, fixed cable (2 m) plug F 6.0229.020 iSolvotrode 6.0279.3001 dSolvotrode 6.00203.3002 1 Further information about iTrodes can be found on pg. 10. 2 Further information about dTrodes can be found on pg. 8. Special electrodes for pH measurement/pH titration 24 Biotrode – pH measurement in small volumes Technical specifications • Very low immersion depth and very small diameter of Biotrode the electrode tip (3 mm), exceptionally suited to small Shaft material Glass measuring vessels pH range 1...11 • For protein-containing samples and solutions with Temperature range 0...60 °C organic components Diaphragm Platinum wire • Very low electrolyte outflow (Idrolyte) Installation length 113 mm • LL reference system with long-term stability Shaft diameter 12 mm Shaft diameter bottom 3 mm Minimum immersion depth 7 mm Electrode plug-in head Metrohm plug-in head G Spearhead electrode – pH measurement in Technical specifications semi- solid samples Spearhead electrode • Robust electrode tip for measurements in semi-solid Shaft material Glass samples such as cheese, meat, fruits, etc. pH range 1...11 • Maintenance-free reference electrolyte (gel) Temperature range 0...60 °C • Easy-to-clean diaphragm Temperature sensor none / Pt1000 • LL reference system with long-term stability Diaphragm Twin pore • With or without integrated temperature sensor Installation length 98 mm • Lifetime indicator Shaft diameter 12 mm Shaft diameter bottom 6 mm Minimum immersion depth 10 mm Electrode plug-in head Metrohm plug-in head G Flat-membrane electrode – pH measurement on Technical specifications surfaces and in small sample volumes Flat-membrane electrode • For pH measurement on surfaces such as paper, textiles, Shaft material Glass leather or soil samples (aqueous suspensions) pH range 0...13 • Measurement/titration in small sample volumes Temperature range 0...80 °C • Completely made of glass with extremely fine-Diaphragm Fixed ground-joint grounded surface Installation length 125 mm • LL reference system with long-term stability Shaft diameter 12 mm Minimum immersion depth 1 mm Electrode plug-in head Metrohm plug-in head G Porotrode – pH measurement in protein contain- Technical specifications ing samples Porotrode • For pH measurement in very contaminated, protein-Shaft material Glass containing or viscous samples pH range 0...14 • Low-maintenance capillary diaphragm Temperature range 0...80 °C • Polymer electrolyte Porolyte for uniform electrolyte Diaphragm Ceramic capillaries outflow Installation length 125 mm • LL reference system with long-term stability Shaft diameter 12 mm Minimum immersion depth 20 mm Electrode plug-in head Metrohm plug-in head G 25 Biotrode pH measurement in small volumes Spearhead electrode pH measurement in semisolid samples Flat-membrane electrode pH measurement on surfaces Porotrode pH measurement in protein containing samples Ordering information Biotrode, without cable 6.0224.100 Spearhead electrode without temperature sensor, without cable 6.0226.100 Spearhead electrode with Pt1000, without cable 6.00226.600 Flat-membrane electrode, without cable 6.0256.100 Porotrode, without cable 6.0235.200 Special electrodes for pH measurement/pH titration 26 Microelectrode – routine use with sample Technical specifications changers and small vials Microelectrode • For simple acid/base titrations in aqueous solutions Shaft material Glass • Available in various lengths (113/168 mm) pH range 0...14 • LL reference system with long-term stability Temperature range 0...80 °C Diaphragm Ceramic pin Installation length 113/168 mm Shaft diameter 12 mm Shaft diameter bottom 6.4 mm Minimum immersion depth 20 mm Electrode plug-in head Metrohm plug-in head G Viscotrode – universal application in viscous Technical specifications media Viscotrode • For viscous protein- or sulfides- containing media Shaft material Glass • Flexible ground-joint diaphragm, particularly easy to pH range 0...14 clean Temperature range 0...80 °C • LL reference system with long-term stability Diaphragm Flexible ground-joint Installation length 113 mm Shaft diameter 12 mm Minimum immersion depth 30 mm Electrode plug-in head Metrohm plug-in head G Syntrode with Pt1000 – use in Technical specifications synthesis and in bioreactors Syntrode • Low-maintenance thanks to storage vessel for Shaft material Glass reference electrolytes pH range 0...14 • Fixed ground-joint diaphragm insensitive to Temperature range 0...100 °C contamination Temperature sensor Pt1000 • High temperature resistance Diaphragm Fixed ground-joint • Available in various lengths (288/438 mm) Installation length 288/438 mm • LL reference system with long-term stability Shaft diameter 12 mm Minimum immersion depth 25 mm 27 Microelectrode Routine use with sample changers and small vials Viscotrode Universal use in viscous media Syntrode with Pt1000 For use in synthesis and in bioreactors Ordering information Microelectrode, length 113 mm, without cable 6.0234.100 Microelectrode, length 168 mm, without cable 6.0234.110 Viscotrode, without cable 6.0239.100 Syntrode with Pt1000, length 288 mm, without cable, plug-in head U 6.0248.600 Syntrode with Pt1000, length 438 mm, without cable, plug-in head U 6.00249.600 Electrodes for pH titration in HF-containing solutions 28 Solitrode HF Technical Specifications • pH-glass sensor with good resistance in HF-containing Solitrode HF solutions Shaft material PP • Unbreakable plastic shaft pH range 1...12 • Fast response time Temperature range 0...40 °C Reference system LL-System Reference electrolyte c(KCl) = 3 mol/L Diaphragm Ceramic pin Installation length 113 mm Shaft diameter 12 mm Minimum immersion depth 15 mm Electrode plug-in head Metrohm plug-in head G Combined Sb-electrode Technical Specifications • For pH titration in very hygroscopic matrices or in Combined Sb-electrode matrices containing hydrofluoric acid Shaft material PP • Unbreakable plastic shaft pH range 2...11 Temperature range 0...70 °C Reference system LL-System Reference electrolyte c(KCl) = 3 mol/L Diaphragm Ceramic pin Installation length 113 mm Shaft diameter 12 mm Minimum immersion depth 10 mm Electrode plug-in head Metrohm plug-in head G The recommended fi elds of application of the electrodes are illustrated in the following graph: pH value A Sb-electrode B Solitrode HF C pH-glass electrode HF concentration [%] 29 Ordering information Solitrode HF, without cable 6.0223.100 Combined Sb-electrode, without cable 6.0421.100 30 Metal electrodes 31 High-performance metal electrodes for redox and precipitation titration, and water determination according to Karl Fischer. Separate metal electrodes 32 Separate Pt-wire electrode Technical specifications • Electrode tip made of Pt-wire (0.8 x 6 mm) Separate Pt-wire electrode • Auxiliary electrode for differential potentiometry Shaft material Glass Measuring range -2000...2000 mV Temperature range -20...70 °C Installation length 125 mm Shaft diameter 12 mm Minimum immersion depth 10 mm Electrode plug-in head Metrohm plug-in head B Double Pt-sheet electrode Technical specifications • For bivoltammetric titrations Double Pt-sheet electrode Shaft material Glass Measuring range -2000...2000 mV Temperature range -20...70 °C Installation length 101 mm Shaft diameter 12 mm Minimum immersion depth 10 mm Electrode plug-in head Metrohm plug-in head G Separate Ag-ring electrode Technical specifications • For precipitation titrations of halides, sulfides, Separate metal-ring electrodes hydrogen sulfide, mercaptans and cyanides Shaft material Glass • Available with or without Ag2S coating Measuring range -2000...2000 mV (specify when ordering) Temperature range -20...80 °C Installation length 125 mm Separate Pt-ring electrode Shaft diameter 12 mm • For all standard redox titrations Minimum immersion depth 7 mm Electrode plug-in head Metrohm plug-in head G Double Au-ring electrode • For bivoltammetric titrations • Well suited for Vitamin C determination with DPIP (2,6-Dichlorophenolindophenol) • Minimum immersion depth 20 mm Separate metal-rod electrodes Technical specifications • Consisting of separate electrode shaft made of PP Separate metal-rod electrodes and exchangeable metal-rod (76 mm x 2 mm) made Total length 162 mm of platinum, silver, gold, tungsten or glassy carbon Installation length 140 mm Shaft diameter 12 mm Degree of purity Shaft diameter bottom 8 mm Pt 99.90% Electrode plug-in head Metrohm plug-in head B Ag 99.99% Gold 99.99% W 99.95% 33 Ordering information Separate Pt-wire electrode, without cable plug-in head B 6.0301.100 Double Pt-sheet electrode, without cable 6.0309.100 Separate Ag-ring electrode, without cable 6.00350.100 Separate Pt-ring electrode, without cable 6.0351.100 Double Au-ring electrode, without cable 6.00353.100 Shaft for separate metal-rod electrode, without cable, plug-in head B 6.1241.040 Electrode rod Pt 6.1248.000 Electrode rod Ag 6.1248.010 Electrode rod Au 6.1248.030 Electrode rod glassy carbon 6.1248.040 Electrode rod W 6.1248.050 Titrodes – the maintenance-free metal electrodes 34 Pt-Titrode / Pt-Micro Titrode Technical specifications • For redox titrations without alteration of the pH value Titrodes • For bromatometry, iodometry and cerimetry in com-Shaft material Glass pliance with Pharm. Europe & USP Measuring range -2000...2000 mV • Maintenance-free reference system (pH glass pH range 0...14 membrane) Temperature range 0...80 °C Reference system pH glass electrode Ag-Titrode / Ag-Micro Titrode Installation length 125 mm • For precipitation titrations without alteration of the Shaft diameter 12 mm pH value Minimum immersion depth 20 mm • For precipitation titrations of halides, sulfides, Electrode plug-in head Metrohm plug-in head G hydrogen sulfide, mercaptans and cyanides • For titrations in compliance with Pharm. Europe & USP Micro Titrodes • Available with or without Ag2S, AgCl or AgBr coating Shaft material Glass (specify when ordering) Measuring range -2000...2000 mV • Maintenance-free reference system (pH glass pH range 0...14 membrane) Temperature range 0...80 °C Reference system pH glass electrode Au-Micro Titrode Installation length 178 mm • For ferrometry (determination of the chemical oxygen Shaft diameter 12 mm demand, COD) Shaft diameter bottom 6.4 mm • For the determination of penicillin and ampicillin Minimum immersion depth 20 mm • For titrations with Hg(NO3)2 Electrode plug-in head Metrohm plug-in head G • For redox titrations in the presence of chromium or iron • Maintenance-free reference system (pH glass membrane) • Available in two length (178 mm / 308 mm) Ag-Titrodes: available with or without coating Depending on the application (see application lists), the use of an Ag-Titrode with or without Ag2S, AgBr or AgCl coating is recommended. We would be happy to supply you with your Ag-Titrode with the respective coating at an additional charge; please specify when ordering. 35 Titrodes High performance in redox and precipitation titrations without alteration of the pH value Micro Titrodes Optimized length and diameter of the lower part of the electrode for use in earlier Metrohm sample changer systems Ordering information Ag-Titrode, without cable 6.00430.100 Ag-Titrode, with Ag2S coating, without cable 6.00430.100S Ag-Titrode, with AgBr coating, without cable 6.00430.100Br iAg-Titrode 6.00470.300 iAg-Titrode with Ag2S coating 6.00470.300S dAg-Titrode 6.00404.300 dAg-Titrode with Ag2S coating 6.00404.300S Pt-Titrode, without cable 6.0431.100 iPt-Titrode 6.0471.3001 dPt-Titrode 6.00401.3002 Micro Ag-Titrode, without cable 6.0433.110 Micro Pt-Titrode, without cable 6.0434.110 Micro Au-Titrode, length 178 mm, without cable 6.0435.110 Micro Au-Titrode, length 308 mm, without cable 6.00435.120 1 Further information about iTrodes can be found on pg. 10. 2 Further information about dTrodes can be found on pg. 8. Combined metal electrodes 36 Combined Ag-ring electrode Technical specifications • For precipitation titrations of halides, sulfides, Combined Ag-ring electrode hydrogen sulfide, mercaptans and cyanides with Shaft material Glass alteration of the pH value Measuring range -2000...2000 mV • Available with or without Ag2S or AgBr coating Temperature range 0...70 °C (specify when ordering) Reference system LL system Reference electrolyte c(KNO3) = 1 mol/L Combined Pt-ring electrode Diaphragm Fixed ground-joint • For redox titrations with alteration of the pH value Installation length 125 mm Shaft diameter 12 mm Combined Au-ring electrode Minimum immersion depth 15 mm • For ferrometry (determination of the chemical oxygen Electrode plug-in head Metrohm plug-in head G demand COD) • For determination of penicillin and ampicillin Combined Pt-ring electrode / Au-ring electrode Shaft material Glass Measuring range -2000...2000 mV Temperature range -5...80 °C Reference system LL system Reference electrolyte c(KCl) = 3 mol/L Diaphragm Ceramic pin Installation length 113 mm Shaft diameter 12 mm Minimum immersion depth 15 mm Electrode plug-in head Metrohm plug-in head G 37 Combined metal-ring electrodes High performance with redox and precipitation titrations with alteration of the pH value Ordering information Combined Ag-ring electrode, without cable 6.00450.100 Combined Ag-ring electrode, with Ag2S coating, without cable 6.00450.100S iAg-ring electrode, combined 6.00450.300 dAg-ring electrode, combined 6.00402.3002 Combined Pt-ring electrode, without cable 6.0451.100 iPt-ring electrode, combined 6.0451.3001 dPt-ring electrode, combinded 6.00403.3002 Combined Au-ring electrode, without cable 6.0452.100 1 Further information about iTrodes can be found on pg. 10. 2 Further information about dTrodes can be found on pg. 8. Electrodes for Karl Fischer titration 38 Double Pt-wire electrodes Indicator electrode for volumetric KF determination Technical specifications • For «Ipol» and «Upol»-mode titrations Measuring range -2000...2000 mV Temperature range -20...70 °C Installation length 96 mm Shaft diameter 8 mm Minimum immersion depth 5 mm Electrode plug-in head Metrohm plug-in head G Indicator electrode for coulometric Technical specifications KF deter mination Measuring range -2000...2000 mV • With standard ground-joint 14/15 Temperature range -20...70 °C Installation length 101 mm Shaft diameter 12 mm Shaft diameter bottom 8.75 mm Minimum immersion depth 10 mm Electrode plug-in head Metrohm plug-in head G Indicator electrode for KF Sample Changers Technical specifications • Fixed cable (length 2 m with plug F) Measuring range -2000...2000 mV Temperature range -20...70 °C Installation length 103 mm Shaft diameter 5.3 mm Minimum immersion depth 10 mm Generator electrodes Generator electrode with diaphragm Technical specifications • Standard ground-joint 29/22 and Metrohm plug-in Temperature range -20...70 °C head G Installation length 108 mm • Requires cable 6.2104.120 for connection with Shaft diameter 24 mm KF Coulometers Minimum immersion depth 15 mm Generator electrode without diaphragm Technical specifications • Standard ground-joint 29/22 and Metrohm plug-in Temperature range -20...70 °C head G Installation length 108 mm • Requires cable 6.2104.120 for connection with Shaft diameter 24 mm KF Coulometers Minimum immersion depth 15 mm 39 6.0344.100 6.0345.100 Ordering information Indicator electrode for KF volumetry, without cable 6.0338.100 Indicator electrode for KF coulometry, without cable 6.0341.100 Indicator electrode for KF Sample Changers, fixed cable (2 m), plug F 6.0340.000 Generator electrode with diaphragm, without cable 6.0344.100 Generator electrode without diaphragm, without cable 6.0345.100 40 41 Electrodes for ion and surfactant analysis Ion-selective electrodes 42 Crystal-membrane electrodes • Robust construction • Can also be used for brief periods in organic solvents • Simple cleaning and renewal of electrode surface with polishing set Polymer-membrane electrodes for K+, NO -3, Na+ and Ca2+ • Robust construction • High selectivity due to ionophores immobilized in the membrane • Short preparation time after conditioning in a standard solution • For aqueous solutions Ammonia-selective gas-membrane electrode • Robust construction • Short preparation time after conditioning in a standard solution • The gas-permeable membrane ensures high selectivity and prevents interferences by the measuring solution Choose the right sensor for your application: NH3-ISE (Low) 6.0506.100 / 6.1255.000 • Clean samples (e.g., drinking water, boiler feed water, etc.) • Faster response time at the detection limit • Lower detection limits • Individually tested and certified • Complete modules for simple exchange NH3-ISE (High) 6.0506.150 / 6.1255.050 • Waste water samples • For long-term measurements, monitoring • Faster response times after measuring high ammonium concentrations • Better signal stability at high ammonium concentrations • Affordable exchange of contaminated membranes (e.g., oil residues) 43 Ion Article no. Membrane Min. Installation- Shaft- Tempera- Measure- pH range material im mer sion length diameter ture range ment range depth (mm) (mm) (mm) (°C) (mol/L) Ag+ 6.0502.180 Crystal 1 125 12 0...80 10–7...1 2...8 Br– 6.0502.100 Crystal 1 125 12 0...50 10–6...1 0...14 Ca2+ 6.0510.100 Polymer2 10 113 12 0...40 5*10–7...1 2...12 Cl– 6.0502.120 Crystal 1 125 12 0...50 10–5...1 0...14 CN– 6.0502.130 Crystal 1 125 12 0...80 8*10–6...10–2 10...14 Cu2+ 6.0502.140 Crystal 1 125 12 0...80 10–8...10–1 2...12 F– 6.0502.150 Crystal 1 125 12 0...80 10–6...sat. 5...7 I– 6.0502.160 Crystal 1 125 12 0...50 5*10–8...1 0...14 K+ 6.0510.110 Polymer3 10 113 12 0...40 10–7...1 2.5...11 Na+ 6.0508.100 Polymer 1 125 12 0...40 5*10–6...1 2...12 NH + 4 6.0506.100 Gas membrane 5 125 12 0...50 5*10–6…10–2 11 NH + 4 6.0506.150 Gas membrane 5 125 12 0…50 10–4…1 11 NO – 3 6.00510.120 Polymer1 10 113 12 0...40 10–6...1 2.5...11 Pb2+ 6.0502.170 Crystal 1 125 12 0...80 10–6...10–1 4...7 S2– 6.0502.180 Crystal 1 125 12 0...80 10–7...1 2...12 1 Combined sensor. Ceramic pin diaphragm; electrolyte c(KCl) = 3 mol/L. 2 Combined sensor. Ceramic pin diaphragm; electrolyte c(NH4NO3) = 1 mol/L. 3 Combined sensor. Ceramic pin diaphragm; electrolyte c(CH3COOLi) = 1 mol/L. Accessories for ion-selective electrodes 44 LL ISE reference 6.0750.100 LL ISE Reference Double-junction Ag/AgCl reference electrode with fixed A stable, reproducible reference potential is very impor-ground-joint diaphragm and optimized length for sample tant at low ion concentrations, low ionic strengths and changer applications. Standard bridge electrolyte: especially with repeated determinations using sample c(KCl) = 3 mol/L. changer systems. For this reason Metrohm recom- mends reference electrodes with a fixed ground-joint diaphragm for working with ion-selective electrodes. In addition to a constant electrolyte outflow of approx. 5...30 μL/h, these electrodes are also considerably less influenced by either the ionic strength of the sample solution or the stirring speed than other types of reference electrodes. Accessories for ion-selective electrodes 6.1255.000 Membrane module kit „low“ for 6.0506.1X0, consisting of 3 certified, complete membrane modules + 50 mL inner electrolyte 6.1255.050 Membrane module kit „high“ for 6.0506.1X0 consisting of 1 module and 20 membranes 6.2316.030 Inner filling solution for NH3- sensors 6.2328.000 Electrolyte c(CH3COOLi) = 1 mol/L for combined K-ISE 6.2327.000 Electrolyte solution c(NH4NO3) = 1 mol/L for combined Ca-ISE 6.2308.020 Electrolyte solution c(KCl) = 3 mol/L for combined NO3-ISE 6.2802.000 Polishing set for crystal-membrane electrodes 6.0502.1X0 (approx. 2 g AI2O3 and polishing cloth) Ion standards 6.2301.060 Potassium chloride standard, c(KCl) = 0.1 mol/L, 250 mL 45 Spoilt for choice! To what must I pay particular attention in an ion determination? Precision? Time needed? Costs? Which method is the most suitable for my application? Titration? Direct measurement? Standard addition? ISA? TISAB? When is their use advisable? Which solution do I need for my application? You will find the answers to these questions along with many other useful tips for ion determination with ion-selective electrodes from Metrohm in the theoretical part in section 1.3.3. «Ion-selective electrodes.» Electrodes for surfactant titration 46 Surfactant electrodes for two-phase titration Surfactrode Refill Technical specifications • Refillable surfactant electrode for the titration of ionic Shaft material PEEK surfactants in non-aqueous solvents pH range 0...13 • Renewable electrode surface, therefore practically Temperature range 0...40 °C unlimited working life Installation length 125 mm • Resistant to virtually all conventional solvents used in Shaft diameter 12 mm surfactant analysis (not to chloroform) Minimum immersion depth 1 mm • Particularly suitable for titration of detergents and soap Electrode plug-in head Metrohm plug-in head G Surfactrode Resistant Technical specifications • Durable surfactant electrode for the two-phase Shaft material POM titration of anionic and cationic surfactants in pH range 0...10 non-aqueous solvents Temperature range 10...50 °C • Easy to clean and low-maintenance, therefore particularly Installation length 108 mm suitable for use in sample changer systems Shaft diameter 12 mm • Resistant to chloroform and all solvents used in sur-Minimum immersion depth 5 mm factant analysis Electrode plug-in head Metrohm plug-in head G • Particularly suitable for samples containing oil such as drilling and cutting oils or cooling lubricants Polymer-membrane surfactant electrodes for environmentally-friendly surfactant titration Cationic Surfactant electrode Technical specifications • For the titration of cationic and anionic surfactants in Cationic Surfactant electrode aqueous matrices Ionic Surfactant electrode • Optimized for cationic surfactants NIO Surfactant electrode • Excellent response due to ionophores immobilized in the membrane Shaft material PVC • Long working life with normal use pH range 0...12 Temperature range 0...40 °C Ionic Surfactant electrode Installation length 125 mm • For the titration of anionic and cationic surfactants in Shaft diameter 12 mm aqueous matrices Shaft diameter bottom 2.5 mm • Excellent response due to ionophores immobilized in Minimum immersion depth 20 mm the membrane Electrode plug-in head Metrohm plug-in head G • Long working life with normal use NIO Surfactant electrode • For the titration of non-ionic surfactants in aqueous matrices • For the titration of surfactants based on polyoxy-ethylene adducts • For the titration of pharmaceutical ingredients • Long working life with normal use 47 Ordering information Surfactrode Refill, without cable 6.0507.140 Surfactrode Resistant, without cable 6.0507.130 Cationic Surfactant electrode, without cable 6.0507.150 Ionic Surfactant electrode, without cable 6.0507.120 NIO Surfactant electrode, without cable 6.0507.010 Accessories for surfactant electrodes 48 Refill set for Surfactrode Refill Paste for Surfactrode Refill, 3.5 g 6.2319.000 Filling tool 6.2826.010 Reagents for surfactant titration TEGO trant A100, titrant for anionic surfactants 18 g 6.2317.030 TEGO add, additive for two-phase titration 250 mL 6.2317.120 49 50 51 Reference electrodes – our best references Reference electrodes 52 Double-junction reference electrodes Ag/AgCl reference electrode with Metrohm Technical specifications plug-in head B Shaft material Glass • Easy to change reference and bridge electrolytes Temperature range 0...80 °C • Variable electrolyte outflow at the flexible ground-Diaphragm Flexible ground-joint joint diaphragm Installation length 100/138 mm • Available with 125 mm or 162 mm shaft length Shaft diameter 12 mm • With standard ground-joint 14/15 Shaft diameter bottom 12/8 mm Minimum immersion depth 10 mm Reference system Ag wire + AgCl Electrode plug-in head Metrohm plug-in head B Ag/AgCl reference electrode with Metrohm Technical specifications plug-in head G Shaft material Glass • For differential potentiometry with Metrohm titrators Temperature range 0...80 °C • Easy to change reference and bridge electrolytes Diaphragm Flexible ground-joint • Variable electrolyte outflow at the flexible ground-Installation length 100/138 mm joint diaphragm Shaft diameter 12 mm • Available with 125 mm or 162 mm shaft length Minimum immersion depth 10 mm • With standard ground-joint 14/15 Reference system Ag wire + AgCl Electrode plug-in head Metrohm plug-in head G LL ISE Reference Technical specifications • Double-junction Ag/AgCl reference electrode Shaft material Glass • High signal stability thanks to constant, reproducible Temperature range 0...80 °C electrolyte outflow, therefore particularly suitable for Diaphragm Fixed ground-joint sample changer applications Installation length 125 mm • Fixed ground-joint diaphragm insensitive to Shaft diameter 12 mm contamination Minimum immersion depth 1 mm • Minimum immersion depth of 1 mm Reference system LL system Electrode plug-in head Metrohm plug-in head B 53 Ordering information Ag/AgCl DJ reference electrode, without cable, plug-in head B Length 100 mm, without electrolyte filling 6.0726.100 Length 100 mm, filled with c(KCl) = 3 mol/L 6.0726.107 Length 138 mm, without electrolyte filling 6.0726.110 Ag/AgCl DJ reference electrode, without cable, plug-in head G Length 100 mm, without electrolyte filling 6.0729.100 Length 138 mm, without electrolyte filling 6.0729.110 LL ISE reference, without cable, plug-in head B 6.0750.100 Reference electrodes 54 Modular reference system Technical specifications • Consisting of Ag/AgCl reference system with standard Ag/AgCl reference system ground-joint 14/15 and exchangeable electrolyte vessel Shaft material Glass Temperature range 0...80 °C • Electrolyte vessels without storage vessels, with Shaft length 50 mm ceramic diaphragm, various diaphragm diameters Length to the upper edge Standard ground-joint 43 mm Shaft diameter top 12 mm Shaft diameter bottom 8 mm Minimum immersion depth 20 mm Reference system Ag wire + AgCl Electrode plug-in head Metrohm plug-in head B Electrolyte vessels without storage container Length to the upper edge Standard ground-joint 101 mm Shaft material PTFE/glass Diaphragm Ceramic pin Shaft diameter 3/5.5 mm Diaphragm diameter 3 mm (PTFE)/1 mm (glass) 55 Ordering information Ag/AgCl reference system, without cable, plug-in head B 6.0724.140 Electrolyte vessel made of PTFE without storage vessel, diaphragm diameter 3 mm 6.1240.000 Electrolyte vessel made of glass without storage vessel, diaphragm diameter 1 mm 6.1240.020 56 Electrodes for electrochemistry 57 Electrodes for voltammetric trace analysis, cyclic voltammetric stripping (CVS), cyclic voltammetry and other electrochemical techniques in Metrohm VA instruments or in combination with potentiostats from Metrohm Autolab or Metrohm DropSens. Working electrodes for trace analysis and CVS 58 The electrodes described in the following can be used in various Metrohm voltammetry instruments: 663 VA Stand, 747 VA Stand, 757 VA Computrace, 797 VA Computrace, 884 Professional VA, and 894 Professional CVS. Multi-Mode Electrode pro Ordering information • Universally applicable working electrode for Multi-Mode Electrode pro 6.1246.120 polarography and voltammetry Glass capillaries, not silanized, 10 units 6.1226.030 • Determination of heavy metal ions, organic Glass capillaries, silanized, 10 units 6.1226.050 substances, anions • Supplied without glass capillaries Glass capillaries for Multi-Mode Electrode pro Non-silanized glass capillaries • Standard capillary for polarography and stripping voltammetry in alkaline solutions 6.1246.120 • For universal use with all pH values in aqueous and non-aqueous solutions Silanized glass capillaries • Silanized capillaries for stripping voltammetry in acidic to mildly alkaline solutions • Long lifetime Electrodes for mercury-free trace analysis scTRACE Gold Ordering information • Combined gold microwire electrode scTRACE Gold (set of 4) 6.1258.000 • Determination of arsenic, mercury, copper, lead and Holder for scTRACE Gold 6.1241.080 additional heavy metals Carbon screen-printed electrode de DRP-C11L • For laboratory instruments and the 946 Portable VA SPE electrode holder 6.1241.090 6.1241.09 Analyzer with scTRACE Gold measuring head Screen-printed electrodes (SPE) 6.1241.080 + • Cost effective screen-printed electrodes 6.1258.000 • Determination of various heavy metals • Applicable: Electrode standard type and «Work in solution» type • For laboratory instruments with SPE electrode holder and for the 946 Portable VA Analyzer with SPE meas-6.1241.090 uring head + DRP-C11L 6.1204.510 RDE – rotating disk electrodes 59 An RDE consists of a driving axle and an exchangeable electrode tip. Ordering information Drive for rotating disk electrode (RDE): for VA measuring stands 6.1204.210 with mercury contact for VA 6.1204.600 measuring stands 6.1204.220 for Professional VA/CVS systems 6.1204.510 with mercury contact for Professional VA/CVS systems 6.1204.520 Electrode tips for the RDE Order number Electrode tip Applications Determination range 6.1204.600 Glassy carbon Determination of heavy metals with anodic ppb to ppt Ø 2 mm stripping voltammetry (mercury film technique), Shaft made of glass kinetic and thermodynamic studies in electrochemistry 6.1204.130 Silver Determination of halides and pseudohalides ppb to ppt 6.1204.140 Gold Determination of mercury and other metal ions ppb to ppt with anodic stripping voltammetry 6.1204.170 Platinum Determination of organic additives in electroplating ppm to ppt Ø 3 mm baths with cyclic voltammetric stripping polished technique (CVS), kinetic and thermodynamic studies in electrochemistry 6.1204.190 Platinum Determination of organic additives in electroplating ppm to ppt Ø 1 mm baths with cyclic voltammetric stripping polished technique (CVS), kinetic and thermodynamic Shaft made of glass studies in electrochemistry 6.1204.610 Platinum Determination of organic additives in electroplating ppm to ppt Ø 2 mm baths with cyclic voltammetric stripping polished technique (CVS), kinetic and thermodynamic Shaft made of glass studies in electrochemistry Reference and auxiliary electrodes for trace analysis and CVS 60 Reference electrodes Reference electrode made of plastic with ceramic Ordering information diaphragm, filled Ag/AgCl reference electrode 6.0728.120 • Universal double-junction reference electrode for Electrolyte vessel for reference electrode 6.1245.010 voltammetry • Inner system filled with c(KCl) = 3 mol/L • Aqueous solutions, trace and ultra trace ranges • Low carry-over effects, low blank values Reference electrode made of plastic with ceramic Ag/AgCl reference electrode (dry) 6.0728.110 diaphragm, dry Electrolyte vessel for reference electrode 6.1245.010 • Double-junction reference electrode. Reference system dry • Studies in organic solvents with any electrolyte solution • Low carry-over effects, low blank values LL reference electrode made of plastic with LL-Ag/AgCl reference electrode 6.0728.130 ceramic diaphragm, filled Electrolyte vessel for reference electrode 6.1245.010 • Double-junction reference electrode for the analysis of electroplating baths with cyclic voltammetric stripping (CVS) • Inner system filled with c(KCl) = 3 mol/L • Very stable reference potential LL reference electrode made of glass, filled LL-Ag/AgCl (gel) reference electrode 6.0730.100 • Double-junction reference electrode for the studies of electroplating baths with cyclic voltam metric stripping (CVS) • Very stable reference potential • Maintenance-free Reference electrode made of glass with ground- Ag/AgCl reference electrode glass 6.0728.100 joint diaphragm Electrolyte vessel for reference electrode 6.1245.000 • Double-junction reference electrode with dry reference system • For aqueous as well as non-aqueous solutions • Simple electrolyte replacement, low outflow rate Auxiliary electrodes Platinum auxiliary electrode Platinum auxiliary electrode 6.0343.100 • Universal auxiliary electrode for voltammetry • For all applications with the MME as well as with the rotating platinum disc electrode • Robust, easy maintenance Glassy carbon auxiliary electrode Auxiliary electrode holder 6.1241.120 • For all applications with rotating disc electrodes as Glassy carbon rod 6.1247.000 well as with the MME • Inert surface, no contamination of the measuring cell by platinum 6.1245.010 6.124 6.0728.110 + 6.0728.120 61 6.0728.130 6.0728.100 6.0728.1 6.1245.000 6.0730.100 6.0730.1 6.0343.100 6.1241.120 6.1247.000 Electrodes for Metrohm Autolab RDE and RRDE 62 Rotating disk electrode and rotating ring disk electrode measurements are powerful experimental methods in which the electrode rotates while immersed in the solution. This creates a well-defi ned convective drag towards PT.SHEET the surface of the electrode as long as a laminar fl ow is present. Under these conditions, mass transport occurs through convection and diffusion, with both components directly infl uenced by the angular frequency of the electrode. Measurements under hydrodynamic conditions provi- de great benefi ts with respect to static measurements. Because of the increase in mass transport, the relative contributions from the electron transfer kinetics increase. Electrochemical experiments therefore can provide access to kinetic or mechanistic information. RDE/RRDE electrode tips Technical specifications The rotating disk electrode (RDE) consists of an electro-RDE tips de disk inserted in an electrode shaft. The rotating ring Shaft material PEEK disc electrode (RRDE) is based on a similar design with Length 52.5 mm an additional ring electrode located around the disk. The Shaft diameter 10 mm gap between the ring and the disk is typically very small. Disk diameter 3 or 5 mm Disk material Pt, Ag, Au, GC, Cu, Zn, Metrohm Autolab provides a range of electrodes for RDE stainless steel, empty measurements with a wide choice of materials. An emp- Connector M4 thread ty electrode holder suitable for RDE measurement is also available. RRDE electrodes with a Pt ring are available RRDE tips with a choice of disk material. Shaft material PEEK Length 52.5 mm Shaft diameter 10 mm Disk diameter 5 mm Disk material Pt, Au, GC Ring material Pt Connector M4 thread Counter electrode Technical specifications • Pt-sheet counter electrode (8 x 7 mm) Pt sheet electrode Shaft material Glass Temperature range -20…70 °C Installation length 101 mm Shaft diameter 12 mm Minimum immersion depth 10 mm Electrode plug-in head B (4 mm) RDE.GC50 RDE.AG50 RDE.AU50 6.1204.300 63 6.1204.310 6.1204.320 6.1204.330 RRDE.AUPT UPT RRDE.GCPT RRDE GCPT RRDE.PTPT Order number Electrode tip Applications 6.1204.300 Glassy carbon disk (3 mm) Interfacial electrochemistry 6.1204.310 Platinum disk (3 mm) Interfacial electrochemistry 6.1204.320 Gold disk (3 mm) Interfacial electrochemistry 6.1204.330 Silver disk (3 mm) Interfacial electrochemistry RRDE.PTPT Platinum disk (5 mm) and platinum ring Electrocatalysis RRDE.AUPT Gold disk (5 mm) and platinum ring Electrocatalysis RRDE.GCPT Glassy carbon disk (5 mm) and platinum ring Electrocatalysis RDE.AU50 Gold disk (5 mm) Interfacial electrochemistry RDE.AG50 Silver disk (5 mm) Interfacial electrochemistry RDE.GC50 Glassy carbon disk (5 mm) Interfacial electrochemistry RDE.CU50 Copper disk (5 mm) Interfacial electrochemistry RDE.ZN50 Zinc disk (5 mm) Interfacial electrochemistry RDE.STEEL Stainless steel disk (5 mm) Interfacial electrochemistry RDE.BLANK Empty disk (5 mm) – RDE.PT50 Platinum disk (5 mm) Interfacial electrochemistry Microelectrodes 64 Microelectrodes or ultramicroelectrode are electrodes Technical specifications whose dimensions are small enough that their properties Microelectrodes become a function of size. These working electrodes are Shaft material Glass much smaller than typical metallic electrodes. When the Temperature range 0…40 °C dimensions are in the range of 25 μm or lower, the term Length 51.5 mm ultramicroelectrode is preferred. The most common Shaft diameter 5 mm geometry of these electrodes is a disk. Disk diameter 8…1000 μm Disk material Pt, Ag, Au, GC, Ir, Pd Because of their very small size, these electrodes exhibit Connector B (2 mm) particularities with respect to their macroscopic counter-parts: • Mass transport of electroactive species changes from a linear to a spherical diffusion (in case of disk electrodes). This results in an enhancement of the mass transport to and from the electrode surface. • The current measured at such electrodes becomes smaller but is not proportional to the surface area. • The current density increases. PT.25 PT.20 PT.100 PT.50 Moreover, these electrodes are less affected by charging or capacitive currents with the RC constant decreasing with the radius of the disk. This makes them particularly suitable for studying electrochemical reactions with rapid kinetics. These electrodes are also less affected by ohmic drop, which in turn facilitates measurements in low conductivity media. Metrohm Autolab offers a wide range of glass-sealed disk microelectrodes and ultramicroelectrodes of different sizes and materials. Special electrodes can be manufactured upon request. 65 Order number Electrode tip Applications PT.10 Platinum disk (10 μm) Interfacial electrochemistry PT.20 Platinum disk (20 μm) Interfacial electrochemistry PT.25 Platinum disk (25 μm) Interfacial electrochemistry PT.50 Platinum disk (50 μm) Interfacial electrochemistry PT.100 Platinum disk (100 μm) Interfacial electrochemistry PT.200 Platinum disk (200 μm) Interfacial electrochemistry PT.300 Platinum disk (300 μm) Interfacial electrochemistry PT.500 Platinum disk (500 μm) Interfacial electrochemistry PT.1000 Platinum disk (1000 μm) Interfacial electrochemistry AU.10 Gold disk (10 μm) Interfacial electrochemistry AU.25 Gold disk (25 μm) Interfacial electrochemistry AU.40 Gold disk (40 μm) Interfacial electrochemistry AU.50 Gold disk (50 μm) Interfacial electrochemistry AU.100 Gold disk (100 μm) Interfacial electrochemistry AU.200 Gold disk (200 μm) Interfacial electrochemistry AU.300 Gold disk (300 μm) Interfacial electrochemistry AU.500 Gold disk (500 μm) Interfacial electrochemistry AG.25 Silver disk (25 μm) Interfacial electrochemistry AG.30 Silver disk (30 μm) Interfacial electrochemistry AG.100 Silver disk (100 μm) Interfacial electrochemistry AG.300 Silver disk (300 μm) Interfacial electrochemistry IR.75 Iridium disk (75 μm) Interfacial electrochemistry PD.25 Palladium disk (25 μm) Interfacial electrochemistry PD.100 Palladium disk (100 μm) Interfacial electrochemistry PD.300 Palladium disk (300 μm) Interfacial electrochemistry PD.500 Palladium disk (500 μm) Interfacial electrochemistry Electrodes for the electrochemical quartz crystal microbalance 66 The electrochemical quartz crystal microbalance (EQCM) EQCM.CE is widely used to monitor, simultaneously with the electrochemical signal, the change in frequency which is directly related to the mass changes due to deposition or adsorption of a species to or dissolution of a species from the working electrode. The principle of operation of the EQCM relies on the pie-zoelectric properties of the quartz which will oscillate at a given frequency when a sinusoidal external electric fi eld is applied to it. The oscillation frequency of the crystal depends on a number of parameters such as size, the thickness of the crystal, temperature and the oscillating media. Quartz crystals Technical specifications The crystals provided for the Autolab EQCM are AT-cut Quartz crystals crystals (with a small temperature coeffi cient). They are Material Quartz coated with different metals on top of an adhesion layer Quartz diameter 13.66 mm (e.g. Ti or Cr oxides). The crystals will also act as working Quartz thickness 250 μm electrodes (WE) being in contact with the electrolyte so-Electrode diameter 6.80 mm lution, broadening in this way the application areas of Electrode material Gold, Platinum, Carbon this technique. Nominal frequency 6 MHz Technical specifications Reference electrode Reference electrode • Single junction reference electrode for EQCM Reference system LL Ag/AgCl Shaft material Glass Shaft length 55 mm Shaft diameter 4 mm Diaphragm Ceramics Temperature range 0…40 °C Connector B (4 mm) Counter electrode Technical specifications • Gold coil counter electrode for EQCM Counter electrode Material Gold wire Wire diameter 1 mm Length 37.5 mm Coil diameter 8 mm EQCM.REF.EL 67 EQCM.Au EQCM.Pt Order number Electrode tip Applications EQCM.Au EQCM 6 MHz Au/TiO2 quartz crystal, polished Interfacial electrochemistry, electrodeposition EQCM.Pt EQCM 6 MHz Pt/TiO2 quartz crystal, polished Interfacial electrochemistry, electrodeposition EQCM.CE EQCM gold counter electrode Interfacial electrochemistry, electrodeposition EQCM.REF.EL EQCM Ag/AgCl 3 M KCl reference electrode Interfacial electrochemistry, electrodeposition Screen-printed electrodes 68 Screen-printed electrodes (SPEs) are cost-effective dispos-Working electrode made of silver able electrodes specially designed to work with microvol- • WE of 1.6 mm umes of sample which is ideal for research purposes and • Standard type also for teaching electrochemistry. Transparent working electrode There is a wide range of SPEs classified below by its Materials: ITO, PEDOT, gold, carbon working electrode (WE) material and differentiated by • Standard type the configuration of the electrochemical cell. The reference electrode (RE) material in all of them is silver (unless Mediator modified working electrode electrode ref. C11L which is silver / silver chloride) and, Materials: Co-phthalocyanine, meldola’s blue, prussian depending on the model, the auxiliary electrode (AUX) blue, ferrocyanide material can be carbon, gold or platinum. Also depend- • Standard type ing on the model, the substrate material can be ceramics, • MultiAnalysis configuration – dual glass, transparent plastic or white plastic. There are also customized designs available upon request. Biomodified working electrode Materials: Streptavidin, extravidin, glucose sensor, Working electrode made of carbon lactate, uric acid • Standard type • Standard type • Work in solution type • MultiAnalysis configuration – dual • MultiAnalysis configuration - dual • MultiAnalysis configuration - 8X electrochemical cells Nanomodified working electrode • MultiAnalysis configuration - 96X electrochemical Materials: Graphene, graphene oxide, reduced graphene cells oxide, multi-walled carbon nanotubes, single-walled • MultiAnalysis configuration - 4WE sharing AUX and carbon nanotubes, carbon nanofibers, mesoporous car-REF bon, ordered mesoporous carbon, gold nanoparticles, • MultiAnalysis configuration - 8WE sharing AUX and silver nanoparticles, quantum dots, core-shell quantum REF dots, graphene-gold nanoparticles, carbon nanotubes- • Integrated flow-cell gold nanoparticles, carbon nanofibres-gold nanoparticles, gold nanoparticles-streptavidin Working electrode made of gold • Standard type • Standard type • MultiAnalysis configuration – dual • Work in solution type • WE of 1.6 mm Other working electrodes • MultiAnalysis configuration - 8X electrochemical cells Materials: Bismuth oxide, nickel oxide, polyaniline, • MultiAnalysis configuration - 96X electrochemical polypyrrole cells • Standard type • Integrated flow-cell • MultiAnalysis configuration – dual Working electrode made of platinum • Standard type • Work in solution type • MultiAnalysis configuration - 8X electrochemical cells • MultiAnalysis configuration - 96X electrochemical cells • Integrated flow-cell DRP-110 Standard Type DRP-C220AT Work in solution Type DRP-C013 WE of 1.6 mm DRP-X1110 69 MultiAnalysis configuration – dual DRP-8X550 MultiAnalysis configuration – 8X DRP-TLFCL110 electrochemical cells Integrated flow-cell 8W110 MultiAnalysis configuration - 8WE sharing auxiliary and reference electrode 4W110 MultiAnalysis configuration - 4WE sharing auxiliary and reference electrode 96X110 MultiAnalysis config- uration - 96X elec- trochemical cells Ordering information Screen-printed carbon electrode DRP-110 Screen-printed gold electrode / ink AT / work in solution DRP-C220AT Screen-printed silver electrode / d 1.6 mm DRP-C013 Dual screen-printed carbon electrode DRP-X1110 8X Screen-printed platinum electrode DRP-8X550 Thin-layer flow-cell integrated screen-printed carbon electrode (Aux.: C ; Ref.: Ag) DRP-TLFCL110 8 WEs screen-printed carbon electrode (1 AUX.:C; 1 REF.:Ag) DRP-8W110 4 WEs screen-printed carbon electrode (1 AUX.:C; 1 REF.:Ag) DRP-4W110 96X screen-printed carbon electrode DRP-96X110 Interdigitated electrodes/microelectrodes 70 Interdigitated electrodes and microelectrodes offer several advantages, such as working with low volumes of DRP-G-IDECONPT10 sample and avoiding tedious polishing of solid elec- Concentric design trodes. In addition, the interdigitated configuration typically enhances sensitivity and detection limits. Depending on the model, substrate materials can be ceramics, transparent plastic, white plastic or glass. AUX and REF electrodes, in models which have them, are made of gold or platinum. Interdigitated electrodes: gold, platinum • Squared design DRP-PW-IDEAU100 • Concentric design Squared design • With auxiliary and reference electrode • With a platinum heater Interdigitated electrodes: silver, copper • Squared design DRP- G-IDE222 Microelectrodes: gold, platinum With auxiliary and reference electrode DRP-G-MEA555 Microelectrodes Ordering information Interdigitated platinum concentric electrode / 10 microns lines and gaps / glass substrate DRP-G-IDECONPT10 Interdigitated gold electrode / 100 microns lines and gaps / plastic substrate DRP-PW-IDEAU100 Interdigitated gold electrode (Aux.:Au; Ref.:Au) / 10 microns lines and gaps / glass substrate DRP- G-IDE222 Platinum microelectrode array d. 3mm / microholes 10 microns / glass substrate DRP-G-MEA555 71 72 73 Conductivity measuring cells and temperature sensors Conductivity measuring cells for 912/914 meters 74 Four-electrode measuring technique Technical specifications Historically, conductivity measuring cells consists of two 6.0918.040 platinized platinum electrodes (Kohlrausch cell). If other Shaft material Stainless steel electrode materials are used instead of platinized plati-Ideal measuring range 0…300 μS/cm num, errors in measurement results due to polarization Temperature range 0...70 °C are most likely to occur. Temperature sensor Pt1000 Installation length 125 mm However, platinization has drawbacks, platinized elec-Shaft diameter 12 mm trodes are susceptible to encrustation, inclusions and Minimum immersion depth 35 mm also growth of algae, bacteria or mold leading to chang-Cell constant 0.1 cm-1 es in the cell constant. Additionally, the two-electrode measuring technique is affected by field effects thus fal-Technical specifications sifying conductivity values measured close to a wall. 6.0917.080 Shaft material PEEK Therefore, Metrohm introduced the multi-electrode Ideal measuring range 15...2.5*105 μS/cm measurement technique for their instruments. For the Temperature range 0...70 °C 912/914 meters, an electrode based on four-electrode Temperature sensor Pt1000 measurement was developed (6.0917.080). This cell Installation length 125 mm consists of two pairs of electrodes, one pair is used for Shaft diameter 12 mm introducing the generator current, and the other pair is Minimum immersion depth 30 mm recording the measurement voltage. Cell constant 0.5 cm-1 The current flowing in the solution causes a drop in the Technical specifications measured voltage. By knowing this voltage and the gen-6.0919.140 erator current, the conductance and from that the con-Shaft material Glass ductivity can be calculated. Ideal measuring range 102...106 μS/cm Temperature range 0...70 °C In summary, the four-electrode measuring technique Temperature sensor Pt1000 allows an almost polarization free recording of the con-Installation length 125 mm ductance and determinations are more reproducible. Shaft diameter 12 mm Additionally, it enables a very large measuring range. Minimum immersion depth 40 mm Another benefit of this sensor is its PEEK shaft which Cell constant 1.6 cm-1 makes the sensor more robust. 75 Ordering information Conductivity measuring cell (stainless steel) with Pt1000, c = 0.1 cm-1, fixed cable (1.2 m) plug K 6.0918.040 Four-ring conductivity measuring cell with Pt1000, c = 0.5 cm-1, fixed cable (1.2 m) plug K 6.0917.080 Three-ring conductivity measuring cell with Pt1000, c = 1.6 cm-1, fixed cable (1.2 m) plug K 6.0919.140 Conductivity measuring cells for 856 Conductivity Module 76 Five-ring conductivity measuring cells Technical specifications Modern five-ring conductivity measuring cells have line-6.0915.100/6.0920.100 arity ranges that are wider than those of classic conduc-Shaft material PEEK tivity measuring cells and require no additional platiniza-Ideal measuring range 5...2 x 104 μS/cm tion. The current applied to the inner electrode generates Temperature range 0...70 °C a current flow to the outer, grounded electrodes, so that Temperature sensor Pt1000 external influences and measuring errors are minimized. Installation length 125 mm Shaft diameter 12 mm Five-ring conductivity measuring cells supply precise Minimum immersion depth 34 mm measuring values, independent of positioning in the Cell constant 0.7 cm-1 beaker (wall effect). Interferences with the potentiometric measurements are now a thing of the past; conductiv-Technical specifications ity and pH value can now be measured simultaneously in 6.0915.130/6.0920.130 the same beaker. Shaft material PEEK Ideal measuring range 5...105 μS/cm The measuring cells are equipped with a fixed cable and Temperature range 0...70 °C plug N for direct connection to the 856 Conductivity Temperature sensor Pt1000 Module. Installation length 142 mm Shaft diameter 12 mm Minimum immersion depth 50 mm Cell constant 1 cm-1 77 Ordering information Five-ring conductivity measuring cell c = 0.7 cm-1 with Pt1000, fixed cable (1.2 m) plug N 6.0915.100 Five-ring conductivity measuring cell c = 1.0 cm-1 with Pt1000, fixed cable (1.2 m) plug N 6.0915.130 Five-ring conductivity measuring cell c = 0.7 cm-1 with Pt1000, fixed cable (2 m) plug N 6.0920.100 Five-ring conductivity measuring cell c = 1.0 cm-1 with Pt1000, fixed cable (2 m) plug N 6.0920.130 Conductivity measuring cell (stainless steel) with Pt1000, c = 0.1 cm–1, fixed cable (1.2 m) plug N 6.0916.040 Conductivity measuring cells 78 Conductivity measuring cells with temperature sensor Technical specifications Conductivity measuring cell Shaft material PP with Pt1000, c = 0.8 cm–1 Measuring range 1...105 μS/cm • Platinized Temperature range 5...70 °C Installation length 125 mm Shaft diameter 12 mm Minimum immersion depth 35 mm Conductivity measuring cells without temperature Technical specifications sensor Shaft material Glass Conductivity measuring cell c = 10 cm–1 Measuring range 10...106 μS/cm • Platinized Temperature range 5...70 °C Installation length 125 mm Shaft diameter 12 mm Shaft diameter bottom 20 mm Minimum immersion depth 80 mm Technical specifications Conductivity measuring cell c = 0.9 cm–1 Shaft material Glass • Platinized Measuring range 1...105 μS/cm • With standard ground-joint 14/15 Temperature range 5...70 °C • Metrohm plug-in head G Installation length 120 mm • Optimum length for sample changer systems Shaft diameter 12 mm Minimum immersion depth 16 mm Accessories for conductivity measuring cells: Conductivity standard  = 12.87 mS/cm (25° C), 250 mL 6.2301.060 Conductivity standard  = 100 μS/cm (25 °C), 250 mL with DKD certificate 6.2324.010 Conductivity standard  = 100 μS/cm (25 °C), 5 x 30 mL with DKD certificate 6.2324.110 79 Ordering information Conductivity measuring cell, c = 0.1 cm–1, fixed cable (1 m) plug 2 x B (4 mm) 6.0901.040 Conductivity measuring cell, c = 10 cm–1, fixed cable (1 m) plug 2 x B (4 mm) 6.0901.260 Conductivity measuring cell for sample changer, c = 0.9 cm–1, without cable 6.0910.120 Sensors for stability measurement 80 The oxidation stability characterizes the resistance of oils and fats and fatty foods to oxidation. It is a standard parameter for quality control in the production of oils and fats in the food industry or for incoming goods inspection in processing plants. Biodiesel and PVC are also subject to oxidation, which can be determined by stability measurement with biodiesel Rancimats or PCV Thermomats. The determination of the oxidation stability takes place automatically and is measured by means of a conductivity sensor. The exact temperature is of central importance for the measurement. We offer two temperature sensors for determining the temperature compensation in the reaction vessel. A short version for the measurement in the short test tubes and a longer version for the determination of the temperature compensation in longer bio- diesel test tubes. Conductometric measuring cell for 743 Rancimat, Technical specifications 873 Biodiesel Rancimat, 892 Professional Shaft material PP Rancimat, 893 Professional Biodiesel Rancimat, Measuring range 0…400 μS/cm 763 PVC Thermomat and 895 Professional PVC Cell constant 1.1 cm-1 Thermomat Temperature sensor Pt100 for 743 Rancimat, Technical specifications 763 PVC Thermomat, 892 Professional Rancimat Shaft material Stainless steel (AISI 304) or 895 Professional PVC Thermomat Measuring range -200…300 °C • Sensor class B according to EN 60751 (ITS 90), Installation length 175 mm certified Minimum immersion depth 20 mm • Fixed cable with mini DIN plug Shaft diameter 2 mm • Stainless steel shaft Temperature sensor Pt100 for 873 Biodiesel Technical specifications Rancimat or 893 Professional Biodiesel Rancimat Shaft material Stainless steel (AISI 304) • Sensor class B according to EN 60751 (ITS 90), Measuring range -200…300 °C certified Installation length 300 mm • Fixed cable with mini DIN plug Minimum immersion depth 20 mm • Stainless steel shaft Shaft diameter 2 mm 81 Ordering information Conductometric measuring cell for 743, 763, 873, 892, 893 and 895 6.0913.130 Pt100 temperature sensor short for 743, 763, 892, 895 6.1111.010 Pt100 temperature sensor long for biodiesel Rancimats 873, 893 6.1111.020 Accessories SET to determine temperature correction for 743, 763, 892, 895 6.5616.100 SET to determine the temperature correction at 873, 893 6.5616.110 Silicone oil for stability measuring instruments (50 mL) 6.2326.000 Temperature sensor 82 Temperature sensor Pt1000 Technical specifications • Rapid, precise temperature setting Shaft material Glass • Available in various lengths (90/125/178 mm) Temperature range -50...180 °C Installation length 90/125/178 mm Shaft diameter 12 mm Shaft diameter bottom 5/6.4 mm Minimum immersion depth 20 mm Electrode plug-in head Metrohm plug-in head G Temperature sensor Pt1000 steel Technical specifications • The glass-free alternative Shaft material PEEK • Shaft made of PEEK Temperature range -50...100 °C • For use in non-oxidizing media pH 1 - 13 Installation length 140 mm • For temperature measurement in semi-solid materials Shaft diameter 12 mm such as cheese, not in frozen meat or similar Shaft diameter bottom (75 mm) 3 mm Minimum immersion depth 10 mm Temperature sensor Pt1000 for 909 UV Digester Technical specifications • Shaft made of glass Shaft material Glass • Fixed cable with 2 x B (2 mm) plug Temperature range -50...180 °C Installation length 120 mm Shaft diameter 12 mm Shaft diameter bottom 5 mm Minimum immersion depth 20 mm 83 Ordering information Temperature sensor Pt1000, length 125 mm, without cable 6.1110.100 Temperature sensor Pt1000, length 178 mm, without cable 6.1110.110 Temperature sensor Pt1000, length 90 mm, without cable 6.1110.120 Temperature sensor Pt1000, steel, length 140 mm, fixed cable (1.2 m) plug 2 x B (2 mm) 6.1114.010 Temperature sensor Pt1000 for 909, length 120 mm, fixed cable (0.5 m) plug 2 x B (2 mm) 6.1110.010 Sensor for themormetric titration 84 Next to potentiometric titration where a suitable elec-Technical specifications trode is used to measure a potential difference, thermo-6.9011.020 metric titration exists. Thermometric titration monitors Shaft material Glass the change in temperature caused by the reaction Measuring range 0...60 °C enthalpy of the titrant with the analyte (exothermic or Installation length 125 mm endothermic reaction). For this, a very sensitive tempera-Shaft diameter 12 mm ture sensor is used, a thermistor. Minimum immersion depth 15 mm The thermistor is manufactured from sintered mixed 6.9011.040 metal oxide which exhibits a large change of electrical Shaft material PEEK and PVDF resistance for a small temperature change. The thermiscoated glass tor is then encapsulated in a suitable electrically insulat-Measuring range 0...60 °C ing medium with satisfactory heat transfer characteristics Installation length 125 mm and acceptable chemical resistance. Typically, the encap-Shaft diameter 12 mm sulating material is glass, however, when either chemical Minimum immersion depth 15 mm attack or mechanical stress is expected encapsulation in an epoxy resin might be possible. Furthermore, a quick electronic circuit is used to maxi-mize the sensitivity for smallest temperature changes. With this, a resolution of 10-5 K can be achieved. Thermometric titration may be the choice where conventional titration sensors are not suitable for the titration environment or when they deliver unsatisfactory titration results. Examples for thermometric titration: • Total acid number (TAN) according to ASTM D8045 • Total base number (TBN) • Phosphate determination • Sodium determination • Titration of plating baths 85 85 Ordering information Thermoprobe 6.9011.020 Thermoprobe HF 6.9011.040 Sensor for photometry 86 Titration with photometric endpoint detection is an inte-Technical specifications Optrode gral part of many titration methods. The Optrode is a Shaft diameter 12 mm handy sensor that can be used like any other Metrosensor. Installation length 135 mm Both new and existing titration systems can be equipped Shaft material Glass with the Optrode. The power supply comes directly via Measuring range the USB port of a Metrohm instrument (Titrino plus, Dark voltage min. 0 mV Ti-Touch, Titrando, USB sample changer). In the case of Bright voltage max. 800 mV models without a USB port the power can also be sup- Temperature range 0...40 °C plied via an optional USB power adapter. pH range 0...14 Min. immersion depth 30 mm Optrode • Eight wavelengths: 470, 502, 520, 574, 590, 610, 640 and 660 nm • 100% solvent resistant (glass shaft) • Compact and space-saving • Very easy cleaning • Easy change of wavelength with a magnet or software controlled (tiamo 2.5 or higher) Photometric titrations with the Optrode, examples: • Nonaqueous titrations according to USP and EP • Determination of the carboxyl end groups (nonaqueous) • TAN/TBN according to ASTM D974 (nonaqueous) • Chloride in silicone products (nonaqueous) • Sulfate determination • Fe, Al, Ca in cement • Water hardness (total hardness and Ca/Mg) • Chondroitin sulfate according to USP 87 Ordering information Optrode, fixed cable plug F, USB 6.1115.000 Optional USB power adapter 5V 1A (for titrators without USB- connection) 6.2166.000 88 89 Accessories for Metrosensors Accessories for Metrosensors 90 SGJ sleeves for Metrohm electrodes 6.1236.020 SGJ sleeve made of PP, standard ground-joint 14/15 with O-ring 6.1236.030 SGJ sleeve made of PP, standard ground-joint 14/15 with O-ring, for sample changer 6.1236.040 SGJ sleeve made of silicone rubber, standard ground-joint 14/15 6.1236.050 SGJ sleeve made of EVA, standard ground-joint 14/15 Other accessories 6.2008.040 Storage vessel made of PP Length 105 mm Diameter 13 mm Ground-joint taper or standard ground-joint 14/15 6.1243.020 Spare ground-joint diaphragm for Profitrode 6.0255.1XX (glass sleeve and plastic ring) 6.1243.030 Spare ground-joint for reference electrodes 6.0726.1XX and 6.0729.1XX 6.2615.050 Electrode holder for 11 electrodes and 3 x 50 ml buffer bottles 91 6.1236.020 6.1236.030 6.1236.040 6.1236.050 Ion standards, buffer solutions, electrolytes 92 Ion standards (traceable to NIST) Ion Concentration Amount Ordering number KCl 0.1000 ± 0.0005 mol/L 250 mL 6.2301.060 Conductivity standard  = 12.87 mS/cm (25 °C) 250 mL 6.2301.060 Conductivity standard for USP <645> and EP 2.2.38 250 mL 6.2324.010 with DKD-certificate  = 100 μS/cm (25 °C) 5 x 30 mL (sachets) 6.2324.110 Buffer and calibration solutions (traceable to NIST) Article Amount Ordering number Ready-to-use buffer solution pH 4.00 500 mL 6.2307.100 in bottles, colored, with pH 7.00 500 mL 6.2307.110 paper seal pH 9.00 500 mL 6.2307.120 Ready-to-use buffer solution pH 4.00 30 x 30 mL 6.2307.200 in sachets pH 7.00 30 x 30 mL 6.2307.210 with DKD-certificate pH 9.00 30 x 30 mL 6.2307.220 pH 4.00, 7.00, 9.00 10 x 30 mL each 6.2307.230 Redox standard yields with reference electrode Ag/AgCl/c(KCl) = 3 mol/L 250 mL 6.2306.020 U = +250 ± 5 mV (20 °C); can also be used as buffer pH 7 Storage solution, cleaning solution, pHit Kit Electrolyte Amount Ordering number Storage solution for combined pH glass electrodes with 250 mL 6.2323.000 reference electrolyte c(KCl) = 3 mol/L pHit kit Care kit for electrodes, containing 50 mL 50 mL each 6.2325.000 each of cleaning solution, reference electrolyte c(KCl) = 3 mol/L, storage solution, and 2 storage vessels Cleaning solution As addition to the pHit Kit to clean 3 x 50 mL 6.2325.100 combined pH glass electrodes Electrolytes 93 Electrolyte Amount Ordering number KCl 3 mol/L for Ag/AgCl reference systems 250 mL 6.2308.020 1000 mL 6.2313.000 KCl-gel sat. thickened 250 mL 6.2308.030 Idrolyte for 6.0224.100 Biotrode or for pH- 250 mL 6.2308.040 measurement > 80 °C with Unitrode/ Syntrode Porolyte for 6.0235.200 Porotrode 50 mL 6.2318.000 KNO3 1 mol/L reference electrolyte for combined 250 mL 6.2310.010 Ag-electrode and bridge electrolyte for Ag/AgCl reference systems LiClsat in ethanol bridge electrolyte for titrations in 250 mL Contact your nonaqueous solutions and reference Metrohm representative electrolyte for Solvotrodes LiCl 2 mol/L in ethanol bridge electrolyte for titrations in 250 mL Contact your nonaqueous solutions and reference Metrohm representative electrolyte for Solvotrodes Tetraethylammonium bridge electrolyte for titrations in 250 mL 6.2320.000 bromide 0.4 mol/L in nonaqueous solutions and reference ethylene glycol electrolyte for Solvotrodes KCl-gel 3 mol/L only as bridge electrolyte for VA 50 mL 6.2308.060 reference electrodes NH4NO3 1 mol/L reference electrolyte for 6.0510.100 50 mL 6.2327.000 combined Ca-ISE CH3COOLi 1 mol/L reference electrolyte for 6.0510.110 50 mL 6.2328.000 combined K-ISE Electrolyte for NH3-electrodes inner electrolyte for NH3-electrodes 50 mL 6.2316.030 KCl sat. storage of gel electrodes 250 mL 6.2308.000 Electrical connections 94 Connection of pH electrodes, ion-selective electrodes (ISE) and metal electrodes on Metrohm instruments Electrode Cable Order number Measuring device plug-in head Plug-in head G – plug F, 1 m 6.2104.020 For pH/ISE and Ind measuring inputs, Titrinos and Titrandos, Plug-in head G Plug-in head G – plug F, 2 m 6.2104.030 pH-/ion meter from 691 Plug-in head G – plug F, 3 m 6.2104.040 Plug-in head G – plug E (DIN 19262), 1 m 6.2104.050 For Metrohm pH Meter < 691 Plug-in head G – plug E (DIN 19262), 2 m 6.2104.060 Plug-in head G – plug E (DIN 19262), 3 m 6.2104.070 Electrode cables for generator electrodes 6.2104.120 KF Coulometer 6.0342.110, 6.0344.100 and 6.0345.100 pH electrodes with Adapter plug B (2 mm)/4 mm 6.2103.150 Titrinos (Pt1000 only) fixed cable, plug B pH Meter ≤ 744 (2 mm) (Pt1000 only) pH electrodes with Adapter plug B (4 mm)/2 mm (red) 6.2103.130 780/781/Titrandos/ fixed cable plug B Adapter plug B (4 mm)/2 mm (black) 6.2103.140 Ti-Touch/91X meters (4 mm) Pt1000 (2 mm) Plug-in head U Plug-in head U – plug F + 2 x B (2 mm), 1 m 6.2104.600 Plug-in head U – plug F + 2 x B (2 mm), 2 m 6.2104.610 Connection of conductivity measuring cells and temperature sensors to Metrohm instruments Electrode Cable Order number Measuring device plug-in head Plug-in head G – plug 2 x B (4 mm), 1 m 6.2104.080 712 Conductometer, measuring inputs Pt 100/ Plug-in head G Pt1000 (4 mm) Plug-in head G – plug 2 x B (4 mm), 2 m 6.2104.110 Plug-in head G – plug 2 x B (2 mm), 1 m 6.2104.140 780/781/Titrandos/ Ti-Touch/91X meters Pt1000 Plug-in head G – plug 2 x B (2 mm), 2 m 6.2104.150 (2 mm) Connection of reference electrodes and separate metal electrodes on Metrohm devices 95 Electrode Cable Order number Measuring device plug-in head Plug-in head G – plug F, 1 m 6.2104.020 For «Ind.» measuring inputs Plug-in head G of Titrinos and for connection (6.0729.XXX) Plug-in head G – plug F, 2 m 6.2104.030 to a Metrohm differential amplifier Plug-in head G – plug F, 3 m 6.2104.040 Plug-in head B Plug-in head B (4 mm) – plug B 6.2106.020 For measuring input «Ref.» (4 mm), 1 m Plug-in head B (4 mm) – plug B 6.2106.060 (4 mm), 2 m Plug-in head B (4 mm) – plug B 6.2106.050 (4 mm), 3 m Connection of Metrohm electrodes with plug-in head G to devices made by other manufacturers Electrode Cable Order number Measuring device plug-in head Plug-in head G – BNC plug, 1 m 6.2104.090 Orion, Beckman, Corning, Plug-in head G EDT, Fisher, Hanna, Mettler- Toledo, Jenway, Philips, Radiometer, Mitsubishi, SI Analytics, Crison, Kyoto/KEM Plug-in head G – LEMO 6.2104.160 Mettler Plug-in head G – plug E (DIN 19262), 1 m 6.2104.050 Older Metrohm devices, WTW, Knick, SI Analytics Plug-in head G – Radiometer plug, 1 m 6.2104.130 Radiometer, Crison Plug-in head G – US plug, 1 m 6.2104.010 Older Orion, Beckman and Fisher devices 96 Connection of Metrohm electrodes to OMNIS measuring modules Electrode Cable Order number Measuring device plug-in head Plug-in head Q Plug-in head Q – plug P, 0.55 m 6.02104.300 For a digital measuring module of OMNIS Plug-in head Q – plug P, 1.5 m 6.02104.310 Plug-in head G of pH Plug-in head G – plug P, 0.55 m (green) 6.02104.000 For measuring input “INPUT electrode, ISE, metal 1” and “INPUT 2” of an electrodes analog measuring module of OMNIS Plug-in head G – plug P, 1.5 m (green) 6.02104.010 Adapter cable for electrodes with fixed 6.02109.000 cable Plug-in head G of Plug-in head G – plug P, 0.55 m (red) 6.02104.020 For measuring input “INPUT temperature sensor 1” and “INPUT 2” of an analog measuring module of Plug-in head G – plug P, 1.5 m (red) 6.02104.030 OMNIS Plug-in head G of Plug-in head G – plug P, 0.55 m (blue) 6.02104.040 For measuring input “INPUT electrode used for 1” of an analog measuring polarized measure- module of OMNIS ment Plug-in head G – plug P, 1.5 m (blue) 6.02104.050 Adapter cable for electrodes with fixed 6.02109.010 cable Plug-in head U Plug-in head U – plug P, 0.55 m (green/ 6.02104.600 For measuring input “INPUT red) 1” and “INPUT 2” of an analog measuring module of OMNIS Plug-in head U – plug P, 1.5 m (green/ 6.02104.610 red) Plug-in head B Plug B (4 mm) – Plug B (2 mm), 0.55 m 6.02105.000 For measuring input “REF” of the analog measuring module of OMNIS Plug B (4 mm) – Plug B (2 mm), 1.5 m 6.02105.010 How is a Metrosensor made? Our accuracy is not accidental ... 97 Always keep cool! Many years of experience and a steady hand with raw materials guarantee that our chemistry is always correct. The right composition of the glass mixture and the greatest possible care during the melting process ensure the perfect quality of the membrane glass. We know how to do it! Our employees need the right feeling when fusing the membrane glass with the electrode body. That this is not just a matter of luck can be seen from our electrodes at the first glance.. 98 Our employees are only human! In some manufacturing processes, such as grinding our fixed ground-joint diaphragms, even a practiced eye no longer stands a chance. Such tasks are carried out with unrivalled accuracy by the most modern machines. Tried and tested electrodes! Before our electrodes leave our premises they are subjected to a further wet-chemistry computer-supported check. At its conclusion we provide a written confirmation so that you can have complete confidence in our electrodes: each electrode receives its own test certificate. Certificate of origin: Precision and guaranteed reliability – Metrohm stands for the highest quality in ion analysis. Just convince yourself! 1. Fundamentals of potentiometry 1.1. Electrode construction Redox electrode 99 In potentiometry the measuring setup always consists of two electrodes: the measuring electrode, also known as the indicator electrode, and the reference electrode. Both electrodes are half-cells. When placed in a solution together they produce a certain potential. Depending on the construction of the half-cells, the potential produced is the sum of several individual potentials. Potential-determining transitions always occur at the phase boundaries, e.g. between the solution and the electrode Figure 2: Schematic diagram of a redox electrode surface. Measuring electrode – metal electrode (left) pH electrode U1 = redox potential between measuring solution and metal surface Reference electrode – silver/silver chloride (right) U4 = Galvani potential of reference electrode U5 = Diaphragm potential (diffusion potential) aM = Activity of measured ion in sample solution For metal electrodes the potential forming transitions U2 Figure 1: Schematic diagram of a pH electrode and U3 of the pH electrodes do not exist. Depending on the particular application, it may be possible to use a pH Measuring electrode – glass electrode (left) glass electrode as the reference electrode instead of the U1 = Galvani potential between measuring solution silver/silver chloride reference electrode. In the combined and glass membrane redox electrodes and Titrodes from Metrohm the half- U2 = Galvani potential between glass membrane cells are also contained in a single electrode. and inner electrolyte U3 = Galvani potential between inner electrolyte 1.2. From the measured potential to and inner reference electrode the ion concentration As each ion is surrounded by ions with the opposite Reference electrode – silver/silver chloride (right) charge, it is – to put it simply – no longer as effective as U4 = Galvani potential of reference electrode a free ion (see Debye-Hückel law). This affects both the U5 = Diaphragm potential (diffusion potential) reactivity and the size of the potentials at the measuring aM = Activity of measured ion in sample solution electrode. The activity of the measuring ion aM, which is also used in the Nernst equation, is linked to the normally The potentials U2, U3 and U4 can be kept constant by a interesting analytical concentration cM via the activity suitable electrode construction. Constructive measures coefficient : and the selection of a suitable reference electrolyte ensure that U5 is also kept as constant as possible. Ideally aM =  * cM the measured potential should depend only on the (1) potential between the glass membrane and the solution. For practical reasons the half-cells of the measuring electrode and the reference electrode are normally contained in a single electrode; this is then known as a combined pH electrode. 100 For dilute solutions with concentration cM ≤0.001 mol/L absolutely necessary to take the temperature into the activity coefficient  tends towards 1 and the activity account in all direct potentiometric measurements, as of the ion corresponds to its concentration as a first otherwise no correct results will be obtained. approximation.  is a function of the ionic strength of the measuring solution. pH value In practice – particularly when measuring the acid/ base The mathematical relationship between the activity aM of equilibrium – the term pH, introduced by Sörensen in a measuring ion in solution ions and the potential meas-1909, is frequently used instead of the activity of the ured between the reference electrode and the measuring measuring ion aM: electrode is described by the Nernst equation. This applies only for the (ideal) case in which an electrode pH = -log aH+ only responds to a single type of ion. Potentials U2 to U5 (Defi nition of the pH value) (4) for pH electrodes and U4 and U5 for redox electrodes, which are normally constant, appear as potential U0 in The pH value is the negative common logarithm of the the Nernst equation. hydrogen ion activity of a solution. The term p is frequently used for the simplified presentation of very large U = U0 + 2.303 * R * T * log aM or small values. In a similar way pNa+ can be used for the z * F (Nernst equation) (2) activity of sodium ion, or pKA as acid constant or pKB as base constant for reaction constants. In each of these U = measured potential cases what is meant is the negative common logarithm U0 = temperature-dependent standard potential of the particular value. If this definition is inserted in the of electrode Nernst equation then we obtain for the measured R = general gas constant 8.315 J mol-1 K-1 potential U: T = temperature in Kelvin z = ionic charge including sign F = Faraday constant 96485.3 C mol-1 U = U0 – 2.303 * R * T * pH z * F (pH value and potential) (5) The term in the Nernst equation in front of the logarithm is known as the Nernst potential UN (also Nernst slope). Redox potentials (metal electrodes) In a similar way to the Nernst equation (Equation 2) the UN = 2.303 * R * T z equation for the activity-dependent potential is obtained * F (Nernst potential) (3) as follows: Its value is 0.059 V at T = 298.15 K and z = +1. As a fac-U = U0 + 2.303 * R * T * log aox * aH+ tor in the Nernst equation it represents the theoretical z * F ared electrode slope. UN corresponds exactly to the alteration (6) in potential caused by increasing the activity aM by a factor of ten. From the equation it can be seen that the Equation 6 usually allows the potential generated by a electrode slope for electrodes that respond to ions with redox pair at the measuring electrode to be calculated. a double charge (z = 2) is only half the size of that for As protons are involved in most redox reactions, the electrodes for ions with a single charge (z = 1). In addi-measured potential depends on the pH. If proton react-tion, the sign for cation- and anion-sensitive measuring ions cannot be excluded then the pH should also be electrodes is different, as z also takes the charge on the determined or adjusted to a defined value. ion into account. The Nernst potential is directly dependent on the temperature (see Equation 3). This is why it is 1.3. Measuring electrodes why conditioning the electrode in a suitable electrolyte is 101 1.3.1. pH glass electrodes absolutely necessary to ensure an initial solvated layer How does a pH glass electrode work? condition that is as stationary as possible so that results The glass membrane of a pH glass electrode consists of can be obtained that are as reproducible as possible. a silicate framework containing lithium ions. When a glass surface is immersed in an aqueous solution then a glass membrane thin solvated layer (gel layer) is formed on the glass surface in which the glass structure is softer. This applies to inner hydrated layer (approx. 0.0001 mm) electrolyte both the outside and inside of the glass membrane. As the proton concentration in the inner buffer of the electrode is constant (pH 7), a stationary condition is established on the inner surface of the glass membrane. In contrast, if the proton concentration in the measuring solution changes then ion exchange will occur in the outer solvated layer and cause an alteration in the poten-acidic alkaline tial at the glass membrane. Only when this ion exchange has achieved a stable condition will the potential of the Figure 3: The silicate skeleton of the glass membrane contains glass electrode also be constant. This means that the lithium ions, among other things. During the formation of the response time of a glass electrode always depends on solvated layer at the glass surface these are partly replaced by protons. If the concentration of the protons in the solution the thickness of the solvated layer. Continuous contact changes then a new stationary condition must again be with aqueous solutions causes the thickness of the achieved in the solvated layer; this results in a change in solvated layer to increase continuously – even if only very potential at the glass membrane. slowly – which results in longer response times. This is Table 1: Overview of the different electrode membrane glasses used by Metrohm Ltd Application U glass T glass M glass Aquatrode glass E glass (green) (blue) (colorless) (yellow) (yellow) pH range 0...14 0...14 0...14 0...13 0...13 Temperature range 0...80 °C 0...80 °C 0...60 °C 0...80 °C 0...80 °C continuous 0...100 °C short-term Membrane Electrodes with Electrodes with Electrodes with Large surfaces Electrodes with surface large membrane medium to large small membrane medium to large surface membrane surface (micro- membrane surface (mini- electrodes) surface electrodes) Special features For strongly Measurements in Measurements in Responds very Quick response, alkaline solutions, non-aqueous small-volume quickly, so excellent stability long-term meas- sample solutions samples particularly suitable in continuous use urements and for measurements measurements at in ion-deficient or high temperatures weakly buffered solutions Membrane resist- < 500 < 150 < 120 < 250 < 250 ance (MΩ) With reference to sphere membrane 10.5 mm diameter 102 Why are there different types of glass for pH electrodes? Different demands are placed on a pH glass electrode depending on the particular application. Various properties such as response time, thermal resistance, chemical stability, shape, size and electrical properties must all be taken into account in order to have an optimal electrode available to solve each problem. In order to be able to do justice to the numerous applications, different glasses are available with different properties (see table 1). Why must a pH glass electrode be calibrated? Figure 5: In the second calibration step with another buffer The potential of a measuring electrode can always only solution the electrode slope is determined and expressed as a percentage of the theoretical value of 0.059 V (at 25 °C). be given relative to that of a reference electrode. To be able to compare systems, the electrode zero point is defined as being 0 mV for pH 7 and 298.15 K or 25 °C. The electrode zero point is set first (pH 7 corresponding The electrode slope, i.e. the alteration in the measured to 0 mV for Metrosensor pH electrodes). The second and value with the pH, is given by the Nernst equation and at further buffer solutions are used to determine the slope 25 °C is 0.059 V per pH 1. These are ideal values from of the pH electrode. This slope is expressed as a percent-which Metrosensor electrodes only differ slightly. The age of the theoretical value (100% = 0.059 V per ∆pH = electrode zero point is ± 0.015 V. The electrode zero 1 at 25 °C). In order to minimize subsequent measuring point and the electrode slope may change as a result of errors, care should be taken that the expected measured the aging of the glass membrane or changes, (e.g con-value of the sample solution always lies within the pH tamination) on the diaphragm. For this reason the pH range covered by the buffer solutions. Modern pH and meter must be adapted to the characteristics of the ion meters such as the 780 pH Meter, the 781 pH/Ion electrode, i.e. calibrated, at regular intervals by using Meter, the 913 pH meter and 914 pH/conductivity meter buffer solutions. do not require any manual settings to be made. The buffer solutions are recognized automatically and can be presented in any sequence. Calibration always includes a check of the measuring electrode. The calibration buffers have a medium acid-base concentration and their ionic strength is approximately that of the most common sample solutions. The dependency of the electrode slope on the temperature means that the calibration and measuring temperatures must be known. Information about the electrode condition is provided by the electrode slope, electrode zero point, response time of the signal and its streaming dependency. With the Metrohm 781 pH/Ion Meter and 780 pH Meter an automatic electrode test can be carried Figure 4: In the fi rst calibration step with buffer pH = 7 the variation from the electrode zero point (= asymmetry out; this provides an exact statement of the electrode potential) is determined and corrected. condition and often allows a source of error to be local-ized. pH and temperature – an inseparable couple! 103 The temperature has a considerable influence on the pH value and the pH measurement. If an electrode is calibrated at 25 °C then it should be capable of linear measurement throughout the whole pH range and provide correct results. However, if the electrode is then used at a different temperature the electrode slope will change Isotherm – in accordance with the Nernst equation – and possibly intersection the electrode zero point as well. The point at which the two calibration curves (without correction) for different temperatures intersect is known as the isothermal inter-Figure 6: Isothermal intersection point section point. Thanks to the optimized inner buffer and «Long Life» reference system precise measurements can and pH are not measured at the same location. In be made with Metrosensor pH electrodes at different modern pH electrodes the temperature sensor should be temperatures. This means that, although calibration is located within the electrode in the immediate vicinity of only carried out at a single temperature, measurements the glass membrane. This is the only way in which an can then be made throughout the whole temperature accurate pH measurement is possible. If the sensor is range. The real behavior of Metrosensor pH electrodes located outside the membrane then problems when varies from the ideal behavior by maximum ±15 mV. cleaning the electrode could easily occur. Nevertheless it is still true that the accuracy of the measurement is increased when the electrode is calibrated at the temperature to be used for the subsequent measurements. At T = 298.16 K and z = 1, the Nernst potential Table 2: Dependency of the Nernst potential UN on the UN is equal to 59.16 mV. For other temperatures it can be temperature corrected in the Nernst equation by using Table 2. Temperature Slope UN Temperature Slope UN Modern pH meters automatically take the temperature T (°C) (mV) T (°C) (mV) dependency of the Nernst potential into account if a 0 54.20 50 64.12 temperature sensor is connected. In principle, within the 5 55.19 55 65.11 context of GLP/ISO recording and documentation of the 10 56.18 60 66.10 15 57.17 65 67.09 temperature is required for all measurements. 20 58.16 70 68.08 25 59.16 75 69.07 However, it must be remembered that a pH meter can 30 60.15 80 70.07 only correct the temperature behavior of the electrode 35 61.14 85 71.06 and never that of the solution to be measured. For cor-37 61.54 90 72.05 rect pH measurements it is essential that the pH is meas-40 62.13 95 73.04 ured at the temperature at which the sample was taken. 45 63.12 100 74.03 For example, sodium hydroxide c(NaOH) = 0.001 mol/L at 0 °C has a pH of 11.94, at 50 °C it is pH = 10.26 and How to store a pH glass electrode? only at 25 °C is it pH = 11.00. This change in pH is caused The swelling of the glass surface is indispensable for the by the dependency of the ionic product of water on the use of glass as membrane for pH glass electrodes; with-temperature. out this solvated layer, no pH measurement would be possible. Glasses for pH glass electrodes are optimized in In some conventional electrodes the temperature sensor such a way that only protons can penetrate into the glass is not located in the immediate vicinity of the membrane, membrane. However, because of the very slow but i.e. in the electrode foot. This means that it cannot meas-steady swelling of the glass, it is unavoidable that also ure the temperature of the solution correctly and that the other ions penetrate into the glass, e.g. sodium and pH compensation will be incorrect as the temperature potassium ions. At higher concentrations, these lead to 104 the so-called alkali error of the glass electrode. This means that the measured value is falsified at compara-tively low proton concentrations. If the glass electrode is stored for a very long time in a strong solution of potassium or sodium, this leads to prolonged response times Storage solution of the glass membrane since the protons must expulse the «added ions» from the solvated layer. Time/s One of the most used electrolytes for pH measurement is c(KCl) = 3 mol/L, since the aequitransferent KCl causes Figure 8: pH measurement in c(NaHCO3) = 0.05 mmol/L. A only a very small diffusion potential at the diaphragm glass of the Aquatrode stored in the storage solution shows a substantially shorter response time than an electrode glass of and is also economical. Normally a combined pH glass the same type stored during the same period in KCl. electrode is stored in c(KCl) = 3 mol/L only for this reason, as one wants to have it ready for immediate use without conditioning the diaphragm. However, on a long-term response time and alkali error. Moreover, if one uses basis the storage in KCl affects the glass, since it leads to c(KCl) = 3 mol/L as the reference electrolyte, the opti-ever longer response times. For the membrane glass, mized composition of the storage solution keeps the pH storage in distilled water would be optimal, but then the glass electrode ready for measurement. Conditioning diaphragm would have to be conditioned for several before the measurement is not necessary, no matter for hours. The patented storage solution for combined pH how long the electrode has been stored. glass electrodes (6.2323.000) solves exactly this problem. If a combined pH glass electrode is kept in this solution, the glass membrane remains unchanged regarding Table 3: The correct storage of pH glass electrodes Electrode resp. reference electrolyte Storage Separate pH glass electrode Distilled water Combined pH glass electrode with c(KCl) = 3 mol/L, 6.2323.000 Storage solution Porolyte Combined pH glass electrode with another In the respective reference electrolyte reference electrolyte (Idrolyte, non aqueous) Gel (spearhead electrode), Ecotrode Gel 6.2308.000 Electrolyte solution c(KCl) = sat. Troubleshooting hydrated layer The cause of most problems is not to be found in the measuring electrode and its glass membrane, but rather in the reference electrode, as much more critical diaphragm problems can occur there. To avoid incorrect measurements and to increase the working life, attention must still be paid to the following possible sources of error: Figure 7: Cross-section of a pH glass membrane. If several kinds of cations are present in the measuring solution, these compete for the free spaces in the solvated layer. Especially potassium and sodium can penetrate into the glass membrane and prolong the response time. Table 4: Possible sources of error and their remedies for pH glass electrodes 105 Source of error Effects Action Alternatives HF-containing solutions Etching and dissolution Use of the Sb-electrode of the glass membrane g corrosion potential during the measurement/short working life High pH value and high Increased alkali error g Use of electrodes with U alkali content pH too low glass High temperatures Rapid rise in membrane Use of electrodes with U resistance by aging g glass increased polarizability and drift Measurements at High membrane resistance Use of electrodes with low temperature g polarization effects T glass and Idrolyte as reference electrolyte Dry storage Zero point drift Store in water overnight Store in storage solution 6.2323.000 or reference electrolyte Reaction of a solution Slow response, zero point Try other glass types component with the glass shift, slope reduction Non-aqueous media Reduced sensitivity Store in water T glass/non-aqueous electrolyte solution Deposition of solids on Slow response, zero point Solvent or strong acids membrane surface shift, slope reduction Electrostatic charging Slow response No dab-drying of the Grounding of measuring electrode instrument Deposition of proteins on Slow response, zero point 5% pepsin in 0.1 mol/L membrane surface shift, slope reduction HCl Possible sources of error and care information for diaphragm problems are given in Section 1.4. for reference electrodes. 1.3.2. Metal electrodes How does a metal electrode work? Metal electrodes have an exposed metal surface. If ions This concentration-dependent equilibrium is character-of this metal are contained in the sample solution then ized by a corresponding potential E0 (Galvani potential), an equilibrium is formed at the metal surface that e.g. the Ag/Ag+ equilibrium at a silver surface has a value depends on the concentration of the metal ions in the of E0 = 0.7999 V (25°C). If the sample solution does not solution (see «Theory of the electrical double layer» in contain any ions of the corresponding metal then metal electrochemistry textbooks). Metal ions are accepted by electrodes can still form a Galvani potential if a redox the metal surface and simultaneously released into the reaction occurs in the sample solution. solution. S Me Men+ +n ox + n * e– E0 =... * e– Sred (8) (7) 106 The electrode surface is inert to the redox reaction. No In the literature the so-called standard redox potentials E0 metal ions are released from the metal; in this case the can usually be found. metal surface only acts as a catalyst for the electrons. As gold and platinum electrodes are to a large extent Cl2 (g) + 2e– g 2 Cl– E0 = + 1.359 V chemically inert, they are used for the measurement of Fe3+ + e– g Fe2+ E0 = + 0.771 V redox potentials. Silver electrodes are only used as indi-Cd2+ + 2e– g Cd2– E0 = – 0.403 V cator electrodes for titrations. The zero point of these systems is defined (arbitrarily) Calibrating a metal electrode with the standard hydrogen electrode (SHE) which is Redox-buffer solutions (6.2306.020) are used for quickly assigned a standard potential of 0 mV. If electrons are checking metal or redox electrodes. As the potential released by a redox system to the SHE then this is measured in a redox buffer solution is insensitive to the reduced and the redox pair receives a negative sign; if electrode’s surface condition, contamination of the electrons are accepted then the SHE is oxidized and the metal electrode is often not recognized. For this reason result is a redox potential with a positive sign. The stand-redox-buffer solutions are rather more suitable for check-ard hydrogen reference electrode is difficult to handle. ing the reference electrode. If the potential is displaced The specifications of the SHE stipulate that a platinized then the metal electrode is contaminated, the redox platinum wire must be used; this is located in a stream of buffer partly oxidized or the functioning of the reference hydrogen gas at a partial hydrogen pressure of 1.0 bar, electrode is affected. Under no circumstances should the and that the activity of the hydrogen ions in the solution indicated potential be set to the theoretical value. in which the platinized platinum wire is immersed is to be exactly 1.00 mol/L. The normal alternative is the Ag/ If measurements are made in weakly redox-buffered AgCl/KCl reference electrode, which has a potential E0 = solutions then a suitable pretreatment of the metal +207.6 mV at c(KCl) = 3 mol/L and T = 25 °C. The elec trode is recommended to adapt the surface condi-Metrohm redox standard (6.2306.020) can be used for tion as much as possible to the measurement conditions checking separate and combined metal electrodes. (abrasive pretreatment: carefully clean the electrode with Platinum and gold electrodes together with the Ag/AgCl/ abrasive paste). The reference electrode can either be KCl reference electrode (c(KCl) = 3 mol/L and T = 20 °C) checked against a second reference electrode that has produce a potential of +250 ± 5 mV. already been checked in buffer solutions 4 and 7 (re s - ponse behavior and reference potential) or by using the redox buffer. Table 5: Measuring data for 6.2306.020 redox standard as a function of the temperature Temp. (°C) 10 20 25 30 40 50 60 70 mV ± 5 + 265 + 250 + 243 + 236 + 221 + 207 + 183 + 178 pH ± 0.05 7.06 7.02 7.00 6.99 6.98 6.97 6.97 6.98 If instead of an Ag/AgCl/KCl reference electrode c(KCl) = from Metrohm, the correction to be applied is -37 mV. 3 mol/L an Ag/AgCl/KCl reference electrode c(KCl) = sat. The Titrodes are checked by a standard titration as no is used for the measurement then at 25 °C a correction suitable calibration or buffer solutions are available. For of +10 mV must be applied; if the measurement is made example, the certified ion standard c(NaCl) = 0.1 mol/L using an Hg/Hg2Cl2/KCl calomel reference electrode, (6.2301.010) can be titrated with a silver nitrate standard which for toxicological reasons is no longer available solution. Troubleshooting 107 Table 6: Problems encountered when measuring with metal electrodes Electrode Source of error Effects Cleaning Alternatives Ag Electrode poisons Passivation of Ag layer g Cleaning with abrasives such as S2–, I–, Br– slow response Pt/Au Fats or oils Isolating layer g slow Cleaning with solvent response, incorrect potential Weakly redox- Adsorbed ions on the Abrasive, oxidative (for Use of Au or Pt buffered solution surface (e.g. oxides) g oxidizing solutions) or slow response reducing (for reducing solu- tions) pretreatment COD determination Deactivation of Pt Use of Au 1.3.3. Ion-selective electrodes best-known examples of such a cross-sensitivity is the How does an ion-selective electrode work? so-called alkali error of pH glass electrodes. With some An ion-selective electrode (ISE) can selectively recognize types of glass the linear range does not extend through-an ion in a mixture of ions in a solution. There are various out the whole pH range from 0 to 14 and at high pH types of ion-selective electrodes, the most commonly values a departure from linear behavior can be observed. used ones are: The reason for this is that at very low H+-concentrations any alkali ions present in the solution (possibly released Glass membrane framework of silicate glass from the walls of the vessel) will falsify the measured with interstitial sites for H+ and Na+ value. Unfortunately there are only a very few ion-selective electrodes that have a linear range similar to that of Crystal membrane crystal lattice containing defined pH glass electrodes. The use of an ISE is normally restrict-gaps for the ion to be measured ed to a concentration range of 6 to 8 powers of ten. If an ISE is used for a measurement right at the limit of the Polymer membrane polymer membrane containing a linear range then the Nernst equation (Eq. (5), Section molecule (= ionophore) that only 1.2.) must be extended by the contribution made by the binds the ion to be measured particular interfering ion for the evaluation of the measured potential: In contrast to metal electrodes, an ISE does not measure a redox potential. If the ion to be measured is contained U = U0 + 2.303 * R * T * log (aM+KS*aS) in the sample solution then this ion can penetrate the z * F membrane. This alters the electrochemical properties of (Nikolsky equation) (9) the membrane and causes a change in potential. One hundred percent selectivity for exactly one type of ion is KS is the so-called selectivity coefficient of the ion-selec-only possible on rare occasions. Most ion-selective elective electrode for interfering ion S. This is a factor that trodes have «only» a particular sensitivity for a special describes the influence of the interfering ion in relation-type of ion, but also often react with ions with similar ship to the ion to be measured. These selectivity coeffi-chemical properties or a similar structure (see Table 7). cients are known for the most important interfering ions This is why the cross-sensitivity to other ions that may be for an ISE and therefore a simple estimation can be made contained in the sample solution must always be taken as to whether an interfering ion contained in the sample into consideration when selecting an ISE. One of the solution will influence the measured value or not. 108 Direct measurement or standard addition? Sample addition The question often arises as to which determination Similar to standard addition, with the difference that method is most suitable for a particular sample. In prin-defined volumes of the sample solution are added to a ciple there are three different ways of carrying out an ion defined amount of an ion standard. measurement with ion-selective electrodes: Modern ion meters such as the 781 pH/Ion Meter from Direct measurement Metrohm can carry out these addition methods auto- Direct measurement is chiefly of benefit with high sam-matically. The addition of the standard or sample solution ple throughputs or with a known sample solution of a is automatically controlled from the ion meter – by press-simple composition. The ion-selective electrode is cali-ing a single key – and evaluated by using the Nikolsky brated with special standard solutions of the ion to be equation. measured before the measurement itself in a similar way to the calibration of a pH glass electrode and can then be ISA and TISAB – when and why? used for several determinations in series. The activity coefficient of an ion (Section 1.2.) is a function of the ionic strength. For this reason care must be Standard addition taken that ion-selective measurements are always carried Standard addition is recommended whenever a determi-out in solutions with approximately the same ionic nation only needs to be carried out occasionally or when strength. In order to achieve this, the so-called ISA solu-the composition of the sample is unknown. Defined tions (Ionic Strength Adjustor) or TISAB solutions (Total volumes of a standard solution of the ion to be measured Ionic Strength Adjustment Buffer) should be added to are added to the sample solution in several steps. The the sample solution (see Table 7). These are chemically concentration in the original solution can then be calcu-inert and have such a high ionic strength that the ionic lated from the initial potential and the individual poten-strength of the sample solution can be neglected after tial steps after the addition of the standard. The advan-their addition. tage of standard addition is that the ISE is calibrated directly in the sample solution, which eliminates all matrix effects. Table 7: Interfering ions and recommended ISA and TISAB solutions for ion-selective electrodes Ion Membrane pH range1 ISA Most important Remarks material or TISAB2 interfering ions3 Ag+ Crystal 2...8 c(KNO3) = 1 mol/L Hg2+, Proteins 1) The given pH range only Br– Crystal 0...14 c(KNO applies to ion-selective 3) = 1 mol/L Hg2+, Cl–, I–, S2–, CN– Ca2+ Polymer 2...12 c(KCl) = 1 mol/L Pb2+, Fe2+, Zn2+, Cu2+, Mg2+ electrodes from Metrohm AG Cl– Crystal 0...14 c(KNO 2– 3) = 1 mol/L Hg2+, Br–, I–, S2–, S2O3 , CN– 2) Alternatives or more de- CN– Crystal 10...14 c(NaOH) = 0.1 mol/L Cl–, Br–, I–, tailed compositions can be Cu2+ Crystal 2...12 c(KNO3) = 1 mol/L Ag+, Hg2+, S2– found in the manual «Ion F– Crystal 5...7 NaCl/glacial acetic acid/ OH– Selective Electrodes (ISE)», CDTA order number 8.109.8042 I– Crystal 0...14 c(KNO 2– 3) = 1 mol/L Hg2+, S2–, S2O3 , K 3) More detailed informa- + Polymer 2.5...11 c(NaCl) = 0.1…1 mol/L TRIS+, NH + 4 , Cs+, H+ tion about interfering ions Na+ Polymer 3...12 c(CaCl2) = 1 mol/L SCN–, K+, lipophilic ions and other interferences NH + 4 Gas membrane 11 – – can be found in the NO – – 3 Polymer 2.5...11 c((NH4)2SO4) = 1 mol/L Cl–, Br–, NO2 , OAC– manual «Ion Selective Pb2+ Crystal 4...7 c(NaClO Electrodes (ISE)», order 4·H2O) = 1 mol/L Ag+, Hg2+, Cu2+ number 8.109.8042 S2– Crystal 2...12 c(NaOH) = 2 mol/L Hg2+, Proteins Troubleshooting Table 8: Possible sources of interference and remedies for ion-selective electrodes 109 Electrode Source of inter- Effects Action ference Ion-selective crystal Dissolution processes, Rough surface g slow response, Polish with polishing cloth membrane oxidation processes poor detection limits Electrode poisons Formation of more sparingly soluble Polish with polishing cloth, salts on the electrode surface than with mask interfering ion the ion to be measured g zero point shift, reduced linearity range Ion-selective Dissolution processes Diffusion into the membrane or Elimination of interfering polymer membrane dissolution of membrane component components NH3 sensor Volatile bases Electrolyte becomes contaminated g Change electrolyte (amines) displacement of calibration line, limited linearity Surfactants Membrane becomes wetted g Replace membrane slow response 1.4. Reference electrodes Reference electrodes are usually electrodes of the second tion purposes. Some titrations offer the possibility of kind. In this type of electrode a metal electrode is in using pH glass electrodes as reference electrodes. Even if contact with a sparingly soluble salt of the same metal. protons are transferred during the titration it is usually The potential depends only on the solubility of the salt. still possible to make an accurate determination of the As a first approximation, electrodes of the second kind endpoint. do not themselves react with the solution and therefore supply a constant potential. 1.4.1. Silver/silver chloride reference electrode The reference element of the silver/silver chloride refer-The most frequently used reference electrode is the ence electrode is the silver/silver chloride/potassium silver/silver chloride electrode (Ag/AgCl/ KCl). The calomel chloride solution system: Ag/AgCl/KCl. The reference electrode (Hg/Hg2Cl2/KCl), which was formerly widely electrode is usually filled with c(KCl) = 3 mol/L or satu-used, is hardly used at all today as mercury and its salts rated KCl solution. Tables 9 and 10 show the potentials are extremely toxic and all the applications can also be of the reference electrode as a function of the reference carried out with the silver/ silver chloride reference elec-electrolyte and temperature. Each of these values has trode. The standard hydrogen electrode SHE is also an been measured against the standard hydrogen electrode electrode of the second kind. It is only used for calibra-under isothermal conditions. Table 9: Standard redox potentials of the silver/silver chloride reference electrode as a function of the temperature and concentration Temp. (°C) 0 +10 +20 +25 +30 +40 +50 +60 +70 +80 +90 +95 E0 (mV) with +224.2 +217.4 +210.5 +207.0 +203.4 +196.1 +188.4 +180.3 +172.1 +163.1 +153.3 +148.1 c(KCl) = 3 mol/L E0 (mV) with +220.5 +211.5 +201.9 +197.0 +191.9 +181.4 +170.7 +159.8 +148.8 +137.8 +126.9 +121.5 c(KCl) = sat. Table 10: Standard redox potentials of the silver/silver chloride reference electrode as a function of the concentration c(KCl) / mol/L (25 °C) 0.1 1.0 3.0 3.5 sat. E0 (mV) +291.6 +236.3 +207.0 +203.7 +197.0 110 1.4.2. The Metrosensor «Long Life» reference system year the concentration of complexated silver ions in the Most electrodes are equipped with the silver/silver chlo-outer electrolyte has only reached 5% of the saturation ride reference system. The solubility product of silver value. chloride in water is very small (10-10 mol2/L2). In the concentrated, chloride-containing solution of the reference The advantages of the «Long Life» reference systems at a electrolyte soluble complexes of the series (AgCl2)-, glance: (AgCl3)2-, (AgCl4)3- are formed. This means that the reference system poses several problems. Outside the elec- • Long working life of the electrode trode the chloride concentration is frequently lower and • Rapid response to changes in pH the complexed silver chloride precipitates in the region • Rapid response to temperature changes surrounding the diaphragm («liquid junction»). The result: • Less sensitive to electrode poisons, e.g. S2-precipitated silver chloride blocks the diaphragm, and the response time of the pH electrode increases. A further Blocking the diaphragm by crystallized AgCl also affects problem is presented by the dependency of the solubility the electrolyte flow. If the «Long Life» reference system is product of AgCl on the temperature. If the electrode is used then the flow of the KCl solution through the dia-used at a different temperature then the equilibrium that phragm into deionized water only decreases slightly. determines the potential of the reference electrode must be reestablished. The larger the surface with solid AgCl in As in the «Long Life» reference system the silver chloride relationship to the electrolyte volume, the shorter the is present in a smaller volume of potassium chloride time required. The «Long Life» reference system prevents solution, the thermodynamic equilibrium between silver, high concentrations of complexed AgCl from occurring silver chloride (solid) and silver chloride (dissolved) is in the outer electrolyte, as the silver chloride reservoir is established very quickly and the potential of the refer-connected with the outer electrolyte by a highly effective ence electrode becomes stable after a very short time. diffusion barrier. The concentration of the silver complex in the reference electrolyte remains low. Even after one 1.4.3. Diaphragms Faulty measurements, unstable measured values and very long response times usually have their source in the Figure 9: «liquid junction» between the sample solution and the Conventional Ag/AgCl/ AgCl-coated KCl system. The chloride reference electrode. The diffusion, streaming and Donnan Ag-wire concentration outside potentials that occur there – which are normally known the electrode is usu-together as the diaphragm potential – have various ally lower than in the AgCl causes and can result in a very incorrect measured value. electrolyte chamber. The soluble silver chloride diaphragm complexes precipitate The measuring error may assume vast proportions if mea-out in the region surements are made under the following conditions: surrounding the • with a blocked, virtually impermeable diaphragm, diaphragm and may block it. • in ion-deficient solutions with an unsuitable diaphragm, • in strong acids and bases with an unsuitable diaphragm, Ag-wire Figure 10: The Metrohm «Long • in colloidal solutions. Life» reference system. AgCl-cartridge with The dissolved AgCl is diffusion barrier retained in the AgCl car tridge and can no longer block the diaphragm diaphragm. In all such cases errors may occur that cannot be toler-urements. On the other hand, because of their small 111 ated. This is why the following questions must be in the pores and large polar surface (>>500 mm2), ceramic foreground whenever an electrode and therefore the diaphragms tend to become blocked and therefore optimal type of diaphragm are to be selected: should not be used in solutions containing precipitates. • Does the reference electrolyte react with the sample An important advance with regard to the prevention of solution to form a precipitate in the diaphragm? diaphragm blockages by silver chloride and silver sulfide • Does the electrolyte flow alter the composition of has been achieved by the introduction of the «Long Life» the sample solution in an unacceptable way? reference system (see Section «The Metrosensor «Long • Is there a risk of depositing sample solution Life» reference system»). components on the diaphragm? • Is the chemical resistance assured? Ground-joint diaphragms with fixed or separable • Can physical parameters such as flow, pressure or ground-joint temperature cause measuring errors? Ground-joint diaphragms with fixed or separable ground- • Does the process allow cleaning/maintenance of the joint are used in ion-deficient media, among others, as electrode at certain intervals? they produce a steady signal that is almost independent • Is a short response time and/or high reproducibility of sample flow conditions. The risk of blockage by silver necessary? chloride or by precipitates formed in the sample solution is relatively low because of the large surface area. The time required for cleaning and maintenance can Streaming potentials, which may occur in measurements usually be considerably reduced if the correct choice of in flowing or stirred solutions, remain negligibly small. electrode is made. The most frequent cause of measuring These properties are particularly important for a SET titra-problems is contamination of the diaphragm. This is why tion to a defined pH or potential value. For example: the with pH electrodes the chief attention is paid to the determination of the carbonate alkalinity by a SET titra-diaphragm during maintenance with the pH membrane tion to pH = 5.4 according to ISO 9963-2 is a widely used being of secondary importance. If existing means cannot method in the routine analysis of drinking water. During be used to determine whether the indicator electrode or a titration it is not possible to dispense with stirring, i.e. the reference electrode requires cleaning/regeneration, with an incorrectly measured pH or potential at the start then it is usually best to treat the reference electrode. of the titration an incorrect endpoint is the inevitable Various types of diaphragm are available to satisfy the result. Figures 11 and 12 clearly show the difference diverse requirements. These requirements have already between the Aquatrode Plus (6.0253.100), which was been taken into consideration for the electrode recom-specially developed for this application, and a conven-mendations in the application lists on pages 6 and 7. tional pH glass electrode with ceramic pin diaphragm. Ceramic pin diaphragms Ceramic pin diaphragms are frequently used diaphragms. They are primarily suitable for clear, aqueous sample solutions. They normally have pore diameters of up to 1 μm with a length and diameter each of about 1 mm. This results in an electrolyte flow rate of up to 25 μL/h, depending on the condition of the diaphragm. This means that the reference electrolyte only requires refilling at long intervals; this is why electrodes with ceramic pin diaphragms are particularly suitable for long-term meas- 112 The ring-shaped geometry and the small polar surface of the ground-joint diaphragm have a favorable effect on the measurement. The increased electrolyte flow influences the sample solution more than if a ceramic pin start pH diaphragm was to be used, the reference electrolyte Ceramic pin diaphragm normally needs refilling on a daily basis during long-term measurements. An alternative is the easyClean diaphragm. It allows easy, stirring speed contact-free cleaning just by pressing once on the electrode head. The spring in the electrode head returns to Figure 11: Measured pH of a solution with c(Na2CO3) = 0.14 mmol/L. Even under vigorous stirring the Aquatrode Plus the defined starting position thereby ensuring greater deviates by only approx. 0.05 pH units (corresponding to accuracy and reproducibility of the electrolyte outflow. approx. 3 mV) from the unstirred value, in contrast the pH glass electrode with ceramic pin diaphragm deviates by approx. Capillary diaphragms 0.2 pH units. In pH measurements in critical samples the very small pores of conventional ceramic diaphragms are easily blocked. The concept that has been realized in the Porotrode (6.0235.100), with two capillaries and a flow rate of 15...25 μL/h ensures unhindered contact between the reference electrolyte and the sample solution (liquid/ liquid phase boundary), while the two capillaries of the EP volume / mL Ceramic pin diaphragm Porotrode are practically insensitive to contamination. The reference electrode is filled with Porolyte, which has been specially developed for this electrode. The constant stirring speed flow of Porolyte ensures that the potential is established quickly and reproducibly. The flow rate and therefore the Figure 12: Endpoint volumes of a SET titration of a solution refilling intervals are comparable to those of conven-with c(Na2CO3) = 0.14 mmol/L with the titrant c(H2SO4) = 0.035 tional electrodes. Extra maintenance work is not neces-mol/L to pH 5.4. The endpoints of the Aquatrode Plus are virtually independent of the stirring speed. At higher stirring speeds sary. Measurements in problematic samples can be the deviation from the theoretical value of the pH electrode carried out easily and reproducibly thanks to the concept with ceramic diaphragm amounts to approx. 5%. that has been realized in the Porotrode. The pH of samples containing protein, such as milk and beer, can now Fixed ground-joint diaphragms have a uniform and re - be determined without any diaphragm problems. In pro ducible electrolyte flow and are therefore particularly contrast to traditional pH electrodes the Porotrode meas-suitable for use with sample changers. ures correctly even at high surfactant concentrations. Separable ground-joint diaphragms are easy to clean and therefore particularly suitable for applications where contamination of the diaphragm cannot be prevented. The electrolyte flow may reach up to 100 μL/h and is nor- mally considerably higher than the amount of electrolyte flowing from a ceramic or fixed ground-joint diaphragm. Twin pore long-term behavior: even when used in difficult media 113 Measuring the pH in semi-solid samples such as cheese, the electrode zero point retains its long-term stability. meat and fruit places special demands on an electrode. The use of polymer electrolytes means that refilling a Proteins, fats and carbohydrates and other semi-solid liquid reference electrolyte is no longer necessary. substances in foodstuffs tend to block the fine pores of the ceramic diaphragms used in most pH electrodes, as The new Ecotrode Gel electrodes (6.0221.x00) are such substances adhere extremely well to the fine-pore equipped with this diaphragm which keeps maintenance ceramic surface. With the development of the spearhead effort low. electrode (6.0226.100) and the polymer electrolytes this problem has been elegantly eliminated: two pinhole Plied platinum wire diaphragms take over the function of the «liquid junc-In combination with the reference electrolyte Idrolyte, tion» between the sample and the reference electrode. which contains glycerol, the plied-platinum-wire dia-The polymer electrolyte adjacent to the openings, which phragm is outstandingly suitable for applications in bio-is spiked with potassium chloride and thickened, is to a logical media. The precipitation of proteins is suppressed large extent insensitive to contamination by media con-by using an electrolyte with a low KCl content. The taining proteins and fats. This insensitivity to contamina-multi-capillary system (channels between the platinum tion, the efficient protection of the reference electrode wires) reduces contamination effects and the electrically against the penetration of electrode poisons and the conductive platinum reduces the response time and the optimized inner buffer of the measuring electrode ensure diaphragm resistance. However, cross-sensitivity may that the new spearhead electrode has an outstanding occur in strongly redox-buffered solutions. Cleaning and care of diaphragms Table 11: Recommended ways of cleaning diaphragms Type of diaphragm Type of contamination Cleaning General Preventiv and regular care pHit kit (6.2325.000) according to instructions Precipitates of silver halides Immerse diaphragm for several hours in and silver sulfides a solution of 7% thiourea in 0.1 mol/L HCl. Proteins, polypeptides Immerse diaphragm for several hours in a solution of 5% pepsin in 0.1 mol/L HCl. Suspensions, solids, resins, Clean electrode with suitable solvent glues, oils, fats Fixed ground-joint All types of contamination Aspirate off reference electrolyte and immerse electrode in the corresponding cleaning solution. Separable ground-joint All types of contamination Loosen the ground-joint sleeve (using hot water if necessary) and clean according to the type of contamination. Capillary Electrolyte flow interrupted Apply slight counterpressure to electrolyte refilling opening 114 1.4.4. Reference electrolytes and bridge electrolytes extent achieved by the use of c(KCl) = 3 mol/L. On the The reference or bridge electrolyte is in electrical contact one hand the ionic mobilities of K+ and Cl– are practically with the sample solution via the diaphragm. The sample the same, on the other hand the ionic concentration in solution and electrolyte form a phase boundary with the sample solution is normally negligibly low in com-different ion concentrations on each side. This difference parison to c(KCl) = 3 mol/L. This is why the equal-trans-in concentration causes diffusion of the ions to the other ference KCl electrolyte is used as standard in all com-side and, because of the different ion mobilities, a bined Metrohm electrodes and reference electrodes. so-called diffusion potential occurs. In order to achieve a However, certain media require the use of other electro-high degree of measuring accuracy the electrolyte com-lyte compositions in order to suppress effects that occur position must be selected so that any diffusion potentials in addition to the diffusion potential. formed are as negligible as possible; this is to a large Table 12: Alternatives to the standard reference electrolyte c(KCl) = 3 mol/L Medium Problems with standard electrolytes Alternative electrolyte c(KCl) = 3 mol/L Silver ions Reaction with Cl– with precipitation of AgCl g slow c(KNO3) = 1 mol/L (or Titrode for response more or less constant pH value) Non-aqueous Precipitation of KCl, solutions and electrolyte c(LiCl) = 2 mol/L in ethanol or LiCl immiscible g unsteady signal saturated in ethanol Ion-deficient water Contamination of the medium by salt g drift KCl solution of lower concentration Proteins/polypeptides Precipitation of the proteins with KCl and AgCl g Idrolyte1 zero point shift/reduced slope Semi-solid substances Contamination of diaphragm g zero point shift/slow Solid electrolyte in combination response with pinhole diaphragm Surfactants (proteins) Adsorption on diaphragm g zero point shift/ Porolyte2 reduced slope 1 Idrolyte is a glycerol-based electrolyte whose chloride ion activity corresponds to that of a KCl solution with c(KCl) = 3 mol/L. This means that the latter can also be readily replaced by Idrolyte. Idrolyte is excellent for use with solutions containing proteins and aqueous solutions with an organic fraction. 2 Porolyte is a KCl solution that has been gelled by polymerization and is used in electrodes with a capillary diaphragm (Porotrode). Table 13: Electrolyte fl ow rates and viscosities Electrolyte Viscosity Flow rate μL/h (10 cm water column) (25 °C) Ceramic pin Flexible ground- Fixed Ceramic Plied Pt (mPas) joint ground- capillary wire joint c(KCl) = ~1 Standard electrode Ø 10 mm: 20...100 5...30 – – 3 mol/L 5...25 Microelectrode 5...15 Ø 5 mm: 5...30 c(KNO3) = ~1 10...25 Ø 10 mm: 20...100 – – – 1 mol/L Ø 5 mm: 5...30 Idrolyte 8...10 – – – – 3...25 Porolyte 1200...1500 – – – 5...30 – 2. Fundamentals of conductometry 2.1. General 115 Conductometry means measuring the conductivity – a c = distance between Pt sheets [cm–1] conductometer measures the electrical conductivity of electrode surface area ionic solutions. This is done by applying an electric field between two electrodes. The ions wander in this field. Cell constant (10) The anions migrate to the anode and the cations to the cathode. In order to avoid substance conversions and the must be known. The result of the measurement is there-formation of diffusion layers at the electrodes (polariza-fore always given as the specific conductivity  with the tion), work is carried out with alternating voltage. The unit Siemens per cm (S·cm–1). rule of thumb is that the frequency of the alternating voltage must be increased as the ion concentration in -  L * c [S cm–1] creases. Modern conductometers automatically adapt Specifi c conductivity (11) the measuring frequency to the particular measuring con ditions. This means that the conductometer must be calibrated before each measurement by determining the cell con- Ion migration in an electric field depends on many fac-stant in a solution of known specific conductivity. The tors. The temperature has a decisive influence on the specific conductivity for various concentrations of many viscosity of the solution and therefore on the mobility of salts is given in tables. The specific conductivity  is the ions. As the temperature increases the viscosity de - linked with the concentration c i of the individual ion i via creases and the conductivity increases. Dissociation con-the concentration-dependent equivalent conductivity  i. stants are also temperature-dependent quantities. This is The equivalent conductivity  i is similar to the activity why it is important to make measurements at a constant coefficient  (see Section 1.2.) and is also a quantity that temperature or to compensate for changes of tempera-depends on the concentration. ture by using the so-called temperature coefficient. The temperature coefficient of most salt solutions is approx. 2%/°C, but depends on the temperature in very dilute  ∑ ( c i i * zi * i) solutions. Specifi c conductivity and concentration (12) The measuring unit used in conductivity measurements is At great dilutions, i.e. c i ≤0.001 mol/L, the equivalent the electrical resistance of the solution. This means that conductivity  i can be equated with the equivalent con-the conductivity is a sum parameter which includes all ductivity shown in the tables for an infinite dilution. dissolved ions. Conductivity cannot be used for the de - termination of a single type of ion, unless the sample is a solution of a single salt or the concentrations of the other ions are known. The reciprocal value of the measured resistance of the solution, the so-called conductance L with the unit Siemens (S = Ω-1) is by itself less meaningful, as the shape of the measuring cell must be taken into account. The cell constant c of a conductometric measuring cell 116 Table 14: Conductivity of various substances and solutions Conductor T () Conductivity due to Conductivity  (μS cm–1) Metallic copper 273 Electron conduction 645,000,000,000 Potassium hydroxide 291 Ionic conduction resulting from the complete 184,000 solution (c = 1 mol/L) dissociation of KOH KCl solution 293 Ionic conduction resulting from the complete 11,660 (c = 0.1 mol/L) dissociation of KCl Brackish water 273 Ionic conduction resulting from the dissociation of salts 20,000 to 1,000,000 and carbonic acid Acetic acid 291 Ionic conduction resulting from the partial dissociation 1300 (c = 1 mol/L) of CH3COOH Drinking water 298 Ionic conduction resulting from the dissociation of salts 10 to 2000 and carbonic acid Graphite 273 Electronic conduction 1200 Distilled water 273 Ionic conduction resulting from contamination 0.06...10 by salts, dissociation of water and carbonic acid Ultrapure water 273 Ionic conduction resulting from low self-dissociation 0.056 Pure benzene 273 Ionic conduction resulting from the dissociation of 0.00000005 traces of water Conductometry is used for direct measurements and in Conductivity measurements titration. The theory is identical for both methods. Whereas the instruments used for potentiometry have Whereas in direct measurements it is the absolute value been standardized (input impedance >1012 Ω, zero that is of interest, in titrations it is the change in the point at pH 7), this is not the case with conductometers. measured value. Direct measurement is often used for The influence of the cable capacity, the measuring fre-monitoring surface waters, waterworks, water desalinaquency level, the conductivity range and the adjustable tion plants and in the preparation of ultrapure water, cell constant, the method used for conductivity measure-where particular limits must not be exceeded. Conductivity ments (phase-sensitive, frequency-dependent, bipolar detection is mostly used for precipitation titrations, pulse, etc.) vary and depend on the type of instrument. where the equivalent point is recognized by the conduc-This means that the instrument must be taken into tivity reaching a minimum value. The absolute value is of ac count for solving application problems. Important secondary importance. parameters are: • Platinizing quality (platinum black) g high series capacity CS • Electrode area A g high series capacity CS • Cell constant c • Measuring frequency f • Cable capacity CP • Cable resistance RC • Instrument measuring range (resistance range) Selecting the right cell constant Interferences, care 117 The cell constant c is defined for conductometric meas-Conductivity measuring cells with Pt sheets uring cells. A measuring cell with two parallel electrodes Conductivity cells have a very porous black platinum at a distance of 1 cm and each with an area of 1 cm2 coating in order to avoid polarization effects in media theoretically has a cell constant c = l · A-1 = 1 cm-1. The with a high conductivity. However, the properties of this cell constant is never exactly l · A-1, as the electric field is coating may change in time (contamination, abrasion of not strictly homogeneous. The rules of thumb given in the platinum coating, etc.); this could alter the cell conTable 15 are used for selecting the correct measuring cell: stant. This is why it is absolutely necessary to calibrate the conductometric measuring cell before making a measurement in order to avoid measuring errors. For the exact determination of cells with a cell constant of <1 cm-1 a solution with a conductivity of about 100 mS/ cm is recommended. If measurements are made in well c(1/cm) conducting media then a check of the activity of the platinum layer is additionally recommended, e.g. in a cell constant 0.1 mol/L KCl solution. If a lower specific conductivity is shown then cleaning with a suitable oxidizing agent or solvent is indicated. If measurements are made in ion-deficient water then specific conductivity K frequent calibration is unnecessary, as in this case the Figure 13: Cell constants and recommended conductivity activity (series capacity) of the platinum layer is not very intervals. important and the deposition of highly isolating sub- stances is not to be expected. The measuring cell must be thoroughly cleaned after calibration in order to avoid incorrect measuring results caused by adherent KCl solution. Table 15: Recommended cell constants Cell constant Sample c = 0.1 cm–1 For very poorly conducting solutions such as distilled water, deionized or partly deionized water, etc. For applications according to USP 645 and EP 2.2.38 c = 1 cm–1 For moderately conducting solutions such as drinking water, surface water, wastewater, etc. c = 10 cm–1 For solutions with good conductivity such as seawater, rinsing water, physiological solutions, etc. c = 100 cm–1 For solutions with very good conductivity such as electroplating baths, salt solutions, etc. 118 Conductivity measuring cells (stainless steel) These are usually substantially more insensitive to con-order to achieve the highest possible measuring accuracy. tamination or corrosion. However, also these measuring For cleaning, water and/or ethanol alone should be used. cells should be calibrated before the measurements in Table 16: Conductivity measurement – interferences Source of Effects Measures interference Low conductivity Values too high, drift Drive off atmospheric CO2 with inert gas with open vessel (Ar, N2) or use flow-through cell, avoid carryover of salt solutions (e.g. too frequent calibration, inadequate rinsing) Oils, precipitation Isolating layer on electrode g Clean with solvent or oxidizing agent products cell constant increases, measuring range limited to higher values Unstable Unstable values Temperature compensation, if temperature temperature coefficient is known, or thermostatting (temperature coefficient generally approx. 2%/°C) Conductance Stray fields outside electrode shaft Watch distance from vessel during depends on (particularly for cells with constants >1 cm-1) calibration and measurement or select electrode position g measured value displaced cell constant 1 cm–1 Use of 5-ring conductivity measuring cells Foreign salts Carryover of residual salts when changing Thorough previous rinsing of electrode to solutions with low conductivity g drift to higher values Air bubbles Air bubble located between Remove air bubble by tapping electrode plates g unsteady signal 2.2. Conductivity measurement in accordance standard are to be used that allow to determine the cell with USP and Pharm. Europe (EP) constant with a maximum measuring error of 2%. To There are special requirements for the conductivity meas-prevent the uptake of carbon dioxide, the measurement urement in water for pharmaceutical use («water for should be carried under exclusion of air and/or in a flow injections») according to USP 645, EP 2.2.38 resp. the cell. The sample fulfills the specification if one of the latest EP -4.8-07/2004:0169. Besides a precision conduc-following three conditions is met: tometer whose temperature compensation can be disa- bled, a conductivity measuring cell and a conductivity Stage 1: Stage 3: 119 The sample is measured directly without further pretreat-However, if the sample does not fulfill the specification ment and without temperature compensation. If the of stage 2, a sample of exactly 100 mL is mixed with water fulfills the specification indicated in table 17, the 0.3 mL saturated KCl solution. Then the pH value of this test is considered as passed. solution is measured exactly to 0.1 pH units. Only if the conductivity fulfills the conditions specified in table 18 Stage 2: the test is considered as passed. Otherwise the water If the conditions are not fulfilled by stage 1, continue as cannot be used for pharmaceutical purposes. follows: The conductivity of at least 100 mL sample is measured under strong agitation at 25 °C ±1 °C as soon as the drift caused by the uptake of carbon dioxide is smaller than 0.1 μS/cm per five minutes. If the measured value is smaller than 2.1 μS/cm, the test is considered as passed. Table 17: First step of the conductivity measurement according to USP 645 and EP -4.8-07/2004:0169 Temperature Conductivity Temperature Conductivity not larger than (μS/cm) not larger than (μS/cm) 0 0.6 55 2.1 5 0.8 60 2.2 10 0.9 65 2.4 15 1.0 70 2.5 20 1.1 75 2.7 25 1.3 80 2.7 30 1.4 85 2.7 35 1.5 90 2.7 40 1.7 95 2.9 45 1.8 100 3.1 50 1.9 Table 18: pH and conductivity criteria for stage 3 pH Conductivity pH Conductivity not larger than (μS/cm) not larger than (μS/cm) 5.0 4.7 6.1 2.4 5.1 4.1 6.2 2.5 5.2 3.6 6.3 2.4 5.3 3.3 6.4 2.3 5.4 3.0 6.5 2.2 5.5 2.8 6.6 2.1 5.6 2.6 6.7 2.6 5.7 2.5 6.8 3.1 5.8 2.4 6.9 3.8 5.9 2.4 7.0 4.6 6.0 2.4 3. Temperature measurement 120 Only a few of the electrodes offered are fitted with a pensation. Under such circumstances it is possible to built-in temperature sensor. The decision whether tem-dispense with the use of a temperature sensor. perature measurement/compensation is necessary de - pends on the required accuracy. Differing diffusion However, if a high degree of reproducibility of the meas-potentials, e.g. in highly concentrated or very dilute solu-ured values is demanded or if GLP requirements have to tions, or changes to the diaphragm or the membrane be met then temperature measurement/compensation is glass can result in measuring errors that are far in excess absolutely necessary. of the errors caused by the absence of temperature com-Table 19: Temperature measurement or temperature compensation: yes or no? Measurement requirements Temperature compensation or measurement Are GLP requirements to be met? Yes: temperature measurement Is high measuring accuracy required? Yes: temperature compensation (see Nernst potential) Direct measurement? Yes: temperature compensation (see Nernst potential) Titration? No: relative measurement Is the pH of the sample about 7? Yes: temperature compensation not absolutely necessary (low influence, as electrode zero point is at pH = 7), possibly temperature measurement Does the pH value differ greatly from pH 7? Yes: temperature compensation (see Nernst potential) Are measurements made at different temperatures? Yes: temperature compensation/measurement (see Nernst potential) Is the pH of the sample solution very temperature- Yes: temperature measurement (measurement dependent? temperature must be mentioned) Does the application require a different type of Yes: separate temperature sensor (electrodes with diaphragm than a ceramic pin? built-in temperature sensors are only available with ceramic pin and fixed ground-joint) Is the working life of the electrode very short? Yes: for cost reduction use separate temperature sensor 121 Technical specifications 122 odes ange short-term (°C) ange long-term (°C) e sensor e r e r atur atur atur ange 6.01 - 6.02 pH glass electr Max. installation length (mm) Shaft diameter (mm) Shaft diameter bottom (mm) Min. immersion depth (mm) Shaft material Plug-in head Temper Temper Temper Shape pH r 6.0150.100 142 12 12 15 Glass G 0...80 0...80 Sphere 0...14 6.0220.100 113 12 12 15 PP G 0...80 0...80 Hemisphere 0...14 6.0221.100 125 12 12 20 Glass G 0...60 0...40 Hemisphere 1...11 6.0221.600 125 12 12 20 Glass U NTC 0...60 0...40 Hemisphere 1...11 6.0223.100 113 12 12 15 PP G 0...40 0...40 Hemisphere 1...12 6.0224.100 113 12 3 7 Glass G 0...60 0...60 Hemisphere 1...11 6.0226.100 98 12 6 10 Glass G 0...60 0...40 Needle 1...11 6.0228.010 113 12 12 15 PP Fixed cable with plug F NTC (2 mm) 0...80 0...80 Hemisphere 0...14 6.0228.020 113 12 12 15 PP Fixed cable with plug I (IP67) NTC (2 mm) 0...80 0...80 Hemisphere 0...14 6.0228.600 113 12 12 15 PP U Pt1000 0...80 0...80 Hemisphere 0...14 6.0229.010 125 12 12 20 Glass Fixed cable with plug F 0...70 0...70 Sphere 0...14 6.0229.020 125 12 12 20 Glass Fixed cable with plug F 0...70 0...70 Sphere 0...14 6.0229.100 113 12 12 30 Glass G 0...70 0...70 Sphere 0...14 6.0233.100 113 12 12 20 Glass G 0...80 0...80 Hemisphere 0...14 6.0234.100 113 12 6.4 20 Glass G 0...80 0...80 Hemisphere 0...14 6.0234.110 168 12 6.4 20 Glass G 0...80 0...80 Hemisphere 0...14 6.0235.200 125 12 12 20 Glass G 0...80 0...80 Hemisphere 0...14 6.0239.100 113 12 12 30 Glass G 0...80 0...80 Hemisphere 0...14 6.0248.600 288 12 12 25 Glass U Pt1000 0...100 0...80 Cylinder 0...14 6.00249.600 438 12 12 25 Glass U Pt1000 0...100 0...80 Cylinder 0...14 6.0253.100 135 12 12 20 Glass G 0...60 0...60 Sphere 0...13 6.0255.100 113 12 12 30 Glass G 0...100 0...80 Cylinder 0...14 6.0255.110 170 12 12 30 Glass G 0...100 0...80 Cylinder 0...14 6.0255.120 310 12 12 30 Glass G 0...100 0...80 Cylinder 0...14 6.0256.100 125 12 12 1 Glass G 0...60 0...60 Flat membrane 0...13 6.00257.000 135 12 12 20 Glass Fixed cable with plug F Pt1000 (2 mm) 0...60 0...60 Sphere 0...13 6.0257.020 260 12 12 20 Glass Fixed cable with plug F Pt1000 (4 mm) 0...60 0...60 Sphere 0...13 6.0257.600 135 12 12 20 Glass U Pt1000 0...60 0...60 Sphere 0...13 6.0258.010 125 12 12 25 Glass Fixed cable with plug F Pt1000 (2 mm) 0...100 0...80 Cylinder 0...14 6.0258.600 125 12 12 25 Glass U Pt1000 0...100 0...80 Cylinder 0...14 6.0259.100 113 12 12 25 Glass G 0...100 0...80 Cylinder 0...14 6.0260.010 125 12 12 20 Glass Fixed cable with plug F Pt1000 0...100 0...100 Hemisphere 0...14 6.0260.020 125 12 12 20 Glass Fixed cable with plug F Pt1000 0...100 0...100 Hemisphere 0...14 6.0262.100 125 12 12 20 Glass G 0...80 0...80 Hemisphere 0...13 6.0269.100 125 12 12 20 Glass G 0...80 0...80 Sphere 0...13 6.0277.300 135 12 12 20 Glass K Pt1000 0...60 0...60 Sphere 0...13 6.0278.300 125 12 12 25 Glass K Pt1000 0...100 0...80 Cylinder 0...14 6.0279.300 113 12 12 30 Glass K 0...70 0...70 Sphere 0...14 6.0280.300 125 12 12 20 Glass K 0...80 0...80 Hemisphere 0...13 6.00200.300 125 12 12 20 Glass Q Pt1000 0...100 0...80 Hemisphere 0...14 6.00201.300 125 12 12 20 Glass Q 0...80 0...80 Hemisphere 0...13 6.00202.300 125 12 12 20 Glass Q Pt1000 0...60 0...60 Sphere 0...13 6.00203.300 125 12 12 20 Glass Q 0...70 0...70 Sphere 0...14 6.00204.300 125 12 12 30 Glass Q 0...100 0...70 Cylinder 0...14 6.00226.600 98 12 6.4 10 Glass U Pt1000 0...60 0...40 Needle 1...11 123 )Ω )Ω μL/h) olyte low ( esistance (M o point (mV) esistance (k ane glass ane r ode zer ode slope agm ence electr olyte outf ence system ence r symmetry potential (mV) Membr Membr Electr Electr A Diaphr Refer Electr Refer Refer T 40...150 ±15 >0.97 ±15 – – – – – T 200...500 ±15 >0.97 ±15 Ceramic c(KCl)=3 mol/L 3...10 LL system 5 E <400 ±15 >0.97 ±15 Twin pore Gel 0 LL system <20 E <400 ±15 >0.97 ±15 Twin pore Gel 0 LL system <20 Spec. 100...650 ±15 >0.97 ±15 Ceramic c(KCl)=3 mol/L 3...10 LL system 5 Spec. 300...600 ±15 >0.97 ±15 Platinum wire Idrolyt 3...30 LL system 30 Spec. 200...500 ±15 >0.97 ±15 Twin pore Gel 0 LL system 20 T 200...400 ±15 >0.97 ±15 Ceramic c(KCl)=3 mol/L 3...10 LL system 5 T 200...400 ±15 >0.97 ±15 Ceramic c(KCl)=3 mol/L 3...10 LL system 5 T 200...400 ±15 >0.97 ±15 Ceramic c(KCl)=3 mol/L 3...10 LL system 5 T 50...150 0...100 >0.90 ±15 EasyClean LiCl/EtOH 3...50 LL system <250 T 50...150 0...100 >0.90 ±15 EasyClean LiCl/EtOH 3...50 LL system <250 T 50...150 0...100 >0.90 ±15 Ground-joint LiCl/EtOH 3...50 LL system <250 T 150...400 ±15 >0.97 ±15 Ceramic c(KCl)=3 mol/L 10...25 LL system 5 T 200...500 ±15 >0.97 ±15 Ceramic c(KCl)=3 mol/L 5...15 LL system 5 T 200...500 ±15 >0.97 ±15 Ceramic c(KCl)=3 mol/L 5...15 LL system 5 T 200...400 ±15 >0.97 ±15 Double capillary (ceramic) Porolyt 5...30 LL system <15 T 150...400 ±15 >0.97 ±15 Ground-joint c(KCl)=3 mol/L 20...100 LL system 5 U 150...500 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 3...30 LL system 5 U 150...500 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 3...30 LL system 5 A 80...200 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L (gel) 5...20 LL system 50 U 150...500 ±15 >0.97 ±15 Ground-joint c(KCl)=3 mol/L 20...100 LL system 5 U 150...500 ±15 >0.97 ±15 Ground-joint c(KCl)=3 mol/L 20...100 LL system 5 U 150...500 ±15 >0.97 ±15 Ground-joint c(KCl)=3 mol/L 20...100 LL system 5 Spec. <2000 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L <2 LL system 5 A 80...200 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L (gel) 5...20 LL system 50 A 80...200 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L (gel) 5...20 LL system 50 A 80...200 ±15 >0.97 ±15 Fixed ground-joint c(KCL)=3 mol/L (gel) 5...20 LL system 50 U 150...500 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 3...30 LL system 5 U 150...500 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 3...30 LL system 5 U 150...500 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 3...30 LL system 5 U 150...500 ±15 >0.97 ±15 EasyClean c(KCl)=3 mol/L 5...50 LL system 5 U 150...500 ±15 >0.97 ±15 EasyClean c(KCl)=3 mol/L 5...50 LL system 5 E 150...400 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 5...30 LL system 5 A 80...200 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 5...30 LL system 10 A 80...200 ±15 >0.97 ±15 Fixed ground-joint c(KCl) = 3 mol/L 5...20 LL system 50 U 150...500 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 3...30 LL system 5 T 50...150 0...100 >0.90 ±15 Ground-joint LiCl/EtOH 3...50 LL system <250 E <400 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 5...30 LL system <5 U <600 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 3...30 LL system 5 E 150...400 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L 3...30 LL system 5 A 80...200 ±15 >0.97 ±15 Fixed ground-joint c(KCl)=3 mol/L (gel) 3...30 LL system 5 T 40...150 10...60 >0.90 ±15 Ground-joint c(LiCl in EtOH)=sat. 0.4...1.2 LL system 100 U 150...500 ±15 >0.97 ±15 Ground-joint c(KCl)=3 mol/L 20...100 LL system 5 Spec. 200...500 ±15 >0.97 ±15 Twin pore Gel 0 LL system 20 Technical specifications 124 ange short-term ange long-term (°C) ate metal ange e r e r odes atur atur ange 6.03 Separ electr Max. installation length (mm) Shaft diameter (mm) Shaft diameter bottom (mm) Min. immersion depth (mm) Shaft material Plug-in head Type Temper (°C) Temper Shape Measuring r pH r 6.0301.100 125 12 12 10 Glass B Pt -20...70 -20...70 Wire -2000...2000 mV 0...14 6.0309.100 101 12 12 10 Glass G Pt -20...70 -20...70 Sheet -2000...2000 mV 0...14 6.0338.100 96 8 8 5 Glass G Pt -20...70 -20...70 Wire -2000...2000 mV 0...14 6.0340.000 103 5.3 5.3 10 Glass Fixed cable/ Plug F Pt -20...70 -20...70 Wire -2000...2000 mV 0...14 6.0341.100 101 12 8.75 10 Glass G Pt -20...70 -20...70 Wire -2000...2000 mV 0...14 6.0343.100 86 8 8 10 Plastic Plug-in connector Pt 0...80 0...80 Rod -2000...2000 mV 0...14 5.5 mm 6.0344.100 108 24 24 15 Glass G Pt -20...70 -20...70 Grid/Sheet 0...14 6.0345.100 108 24 24 15 Glass G Pt -20...70 -20...70 Grid/Sheet 0...14 6.00350.100 125 12 6 7 Glass G Ag -20...80 -20...80 Ring -2000...2000 mV 0...14 6.0351.100 125 12 12 7 Glass G Pt -20...80 -20...80 Ring -2000...2000 mV 0...14 6.00353.100 125 12 6 20 Glass G Au -20...80 -20...80 Ring -2000...2000mV 0...14 125 )Ω )Ω μL/h) olyte ange short-term ange long-term (°C) low ( e r e r ange esistance (k esistance (k odes atur atur agm agm r ange ence electr olyte outf ence system ence r 6.04 Combined metal electr Max. installation length (mm) Shaft diameter (mm) Shaft diameter bottom (mm) Min. immersion depth (mm) Shaft material Plug-in head Type Temper (°C) Temper Shape Measuring r pH r Diaphr Refer Electr Diaphr Refer Refer 6.0421.100 113 12 12 10 Noryl/ G Sb-Stift 0...70 0...70 2...11 Ceramic c(KCl)= 3...10 1.2...1.8 LL system 5 PP 3 mol/L 6.00430.100 125 12 6 20 Glass G Ag/pH 0...80 0...80 Ring/hemi- -2000...2000 0...14 pH 150...400 sphere mV 6.0431.100 125 12 12 20 Glass G Pt/pH 0...80 0...80 Ring/hemi- -2000...2000 0...14 pH 150...400 sphere mV 6.0433.110 178 12 6.4 20 Glass G Ag/pH 0...80 0...80 Ring/hemi- -2000...2000 0...14 pH 200...500 sphere mV 6.0434.110 178 12 6.4 20 Glass G Pt/pH 0...80 0...80 Ring/hemi- -2000...2000 0...14 pH 200...500 sphere mV 6.0435.110 178 12 6.4 20 Glass G Au/pH 0...80 0...80 Ring/hemi- -2000...2000 0...14 pH 200...500 sphere mV 6.00450.100 125 12 6 15 Glass G Ag 0...80 0...80 Ring -2000...2000 0...14 Fixed ground- c(KNO3)= 10...25 0.4...0.9 LL system 5 mV joint 1 mol/L 6.00450.300 125 12 6 15 Glass K Ag 0...80 0...80 Ring -2000...2000 0...14 Fixed ground- c(KNO3)= 10...25 0.4...0.9 LL system 5 mV joint 1 mol/L 6.0451.100 113 12 12 15 Glass G Pt -5...80 -5...80 Ring -2000...2000 0...14 Ceramic c(KCl)= 10...25 0.4...0.9 LL system 5 mV 3 mol/L 6.0451.300 113 12 12 15 Glass K Pt -5...80 -5...80 Ring -2000...2000 0...14 Ceramic c(KCl)= 10...25 0.4...0.9 LL system 5 mV 3 mol/L 6.0452.100 113 12 12 15 Glass G Au -5...80 -5...80 Ring -2000...2000 0...14 Ceramic c(KCl)= 10...25 0.4...0.9 LL system 5 mV 3 mol/L 6.00470.300 125 12 6 20 Glass K Ag/pH 0...80 0...80 Ring/hemi- -2000...2000 0...14 pH 150...400 sphere mV 6.0471.300 125 12 12 20 Glass K Pt/pH 0...80 0...80 Ring/hemi- -2000...2000 0...14 pH 200...500 sphere mV 6.00401.300 125 12 12 20 Glass Q Pt/pH 0...80 0...80 Ring/hemi- -2000...2000 0...14 pH 150...400 sphere mV 6.00402.300 125 12 12 20 Glass Q Ag 0...80 0...80 Ring -2000...2000 0...14 Fixed ground- c(KNO3)= 3...30 < 2 kΩ LL system < 5 kΩ mV joint 1 mol/L 6.00403.300 125 12 12 20 Glass Q Pt -5...80 -5...80 Ring -2000...2000 0...14 Fixed ground- c(KCl)= 3...30 < 2 kΩ LL system < 5 kΩ mV joint 3 mol/L 6.00404.300 125 12 6 20 Glass Q Ag/pH 0...80 0...80 Ring/hemi- -2000...2000 0...14 pH 150...400 sphere mV 6.00435.120 308 12 6.4 20 Glass G Au/pH 0...80 0...80 Ring/hemi- -2000...2000 0...14 pH 200...500 sphere mV Technical specifications 126 ange short-term ange long-term (°C) e r e r ange odes atur atur ange 6.05 Ion-selective electr Max. installation length (mm) Shaft diameter (mm) Shaft diameter bottom (mm) Min. immersion depth (mm) Shaft material Plug-in head Type Temper (°C) Temper Shape Measuring r pH r 6.0502.100 125 12 12 1 EP G Crystal (Br) 0...50 0...50 Flat 1x10–6...1 mol/L 0...14 6.0502.120 125 12 12 1 EP G Crystal (Cl) 0...50 0...50 Flat 1x10–5...1 mol/L 0...14 6.0502.130 125 12 12 1 EP G Crystal (CN) 0...80 0...80 Flat 8x10–6...10–2 mol/L 10...14 6.0502.140 125 12 12 1 EP G Crystal (Cu) 0...80 0...80 Flat 1x10–8...0.1 mol/L 2...12 6.0502.150 125 12 12 1 EP G Crystal (F) 0...80 0...80 Flat 1x10–6...sat. mol/L 5...7 6.0502.160 125 12 12 1 EP G Crystal (I) 0...50 0...50 Flat 5x10–8...1 mol/L 0...14 6.0502.170 125 12 12 1 EP G Crystal (Pb) 0...80 0...80 Flat 1x10–6...0.1 mol/L 4...7 6.0502.180 125 12 12 1 EP G Crystal (Ag/S) 0...80 0...80 Flat 1x10–7...1 mol/L 2...12 6.0506.100 125 12 12 5 PEEK/POM G NH3-permeable 0...50 0...50 Flat 5x10–6...10–2 mol/L 11 membrane 6.0506.150 125 12 12 5 PEEK/POM G NH3-permeable 0...50 0...50 Flat 10–4...1 mol/L 11 membrane 6.0507.010 125 12 2.5 20 PVC G Non-ionic surfactants 0...40 0...40 Pin surfactant- 0...12 dependent 6.0507.120 125 12 2.5 20 PVC G Non-ionic surfactants 0...40 0...40 Pin surfactant- 0...12 dependent 6.0507.130 125 12 12 5 POM G Ionic surfactants 10...50 10...50 Flat surfactant- 0...10 dependent 6.0507.140 125 12 12 1 PEEK G Ionic surfactants 0...40 0...40 Flat surfactant- 0...13 dependent 6.0507.150 125 12 2.5 20 PVC G Ionic surfactants 0...40 0...40 Pin surfactant- 0...12 dependent 6.0508.100 125 12 12 1 PVC G Polymer (Na) 0...40 0...40 Flat 5x10–7...1 mol/L 3...12 6.0508.110 125 12 12 1 PVC G Polymer (Ca) 0...40 0...40 Flat 5x10–6...1 mol/L 2...12 6.0510.100 113 12 12 10 PMMA/PP G Polymer (Ca) 0...40 0...40 Flat 5x10–7...1 mol/L 2...12 6.0510.110 113 12 12 10 PMMA/PP G Polymer (K) 0...40 0...40 Flat 1x10–7...1 mol/L 2.5...11 6.00502.300 113 12 12 10 PMMA/PP Q Polymer (Ca) 0...40 0...40 Flat 5x10–7...1 mol/L 2...12 6.00510.120 113 12 12 10 PMMA/PP G Polymer (NO3) 0...40 0...40 Flat 1x10–6...1 mol/L 2.5...11 127 odes l ) l C Ω C olyte ange short-term (°C) ange long-term (°C) ence electr olyte e r e r esistance (k μL/h) atur atur agm ence electr low ( ence system ence r elation to 3 mol/L K elation to 3 mol/L K 6.07 Refer Max. installation length (mm) Shaft diameter (mm) Shaft diameter bottom (mm) Min. immersion depth (mm) Shaft material Plug-in head Temper Temper Diaphr Refer Bridge electr Outf in r Refer Refer in r 6.0724.140 43 12 8 20 Glass B 0...80 0...80 variable 0 <1 6.0726.100 100 12 12 10 Glass B 0...80 0...80 Ground- variable variable 5...50 Ag wire/AgCl <3 joint 6.0726.107 100 12 12 10 Glass B 0...80 0...80 Ground- c(KCl)=3 mol/L c(KCl)=3 5...50 Ag wire/AgCl <3 joint mol/L 6.0726.110 138 12 8 10 Glass B 0...80 0...80 Ground- variable variable 5...50 Ag wire/AgCl variable joint 6.0727.000 83 18 18 PTCFE Plug pin 2 mm Ceramic c(KCl)=3 mol/L 0 <3 6.0728.100 28 15 7 3 PTCFE Plug-in connector 0...60 0...60 Ceramic variable 1...2,5 Ag wire/AgCl <3 5.5 mm 6.0728.100 58 18 9 3 Plug-in connector variable +6.1245.000 5.5 mm 6.0728.110 53 15 7 3 PTCFE Plug-in connector 0...60 0...60 Ceramic variable 1...2,5 Ag wire/AgCl <3 5.5 mm 6.0728.120 53 15 7 3 PTCFE Plug-in connector 0...60 0...60 Ceramic c(KCl)=3 mol/L 1...2,5 Ag wire/AgCl <3 5.5 mm 6.0728.130 53 15 7 3 PTCFE Plug-in connector 0...60 0...60 Ceramic c(KCl)=3 mol/L 1...2,5 LL system <5 5.5 mm 6.0728.110 65 15 5 3 Plug-in connector variable -6.0728.130 5.5 mm +6.1245.010 6.0729.100 100 12 12 10 Glass G 0...80 0...80 Ground- variable variable 5...50 Ag wire/AgCl <3 joint 6.0729.110 138 12 12 10 Glass G 0...80 0...80 Ground- variable variable 5...50 Ag wire/AgCl <3 joint 6.0730.100 65 12 6 3 Glass Plug-in connector 0...40 0...40 Ceramic c(KCl)=3 mol/L c(KCl)=3 LL system <20 5.5 mm (Gel) mol/L (Gel) 6.0733.100 125 12 5 10 Glass B 0...80 0...80 Ceramic c(KCl)=3 mol/L 5...15 LL system <3 6.0736.110 178 12 6.4 10 Glass B 0...80 0...80 Ground- variable variable 5...50 Ag wire/AgCl <3 joint 6.0750.100 125 12 12 1 Glass B 0...80 0...80 Fixed c(KCl)=3 mol/L c(KCl)=3 3...30 Ag wire/AgCl <40 ground-joint (Gel) mol/L Technical specifications 128 odes, e sensors ange short-term ange long-term (°C) e r e r ange e sensor atur atur atur atur 6.08-6.11 carbon electr Conductivity cells, temper Installation length (mm) Shaft diameter (mm) Shaft diameter bottom (mm) Min. immersion depth (mm) Shaft material Plug-in head Type Temper (°C) Temper Measuring r Temper 6.0901.040 108 12 20 50 Glass Fixed cable 2xB (4 mm) Pt platinized 5...70 5...70 0.1...10000 μS/cm 6.0901.260 125 12 20 80 Glass Fixed cable 2xB (4 mm) Pt platinized 5...70 5...70 10...1000000 μS/cm 6.0908.110 123 12 12 40 Glass Fixed cable 4xB (4 mm) Pt platinized 5...70 5...70 1...100000 μS/cm Pt100 6.0910.120 120 12 12 16 Glass G Pt platinized 5...70 5...70 1...100000 μS/cm 6.0912.110 125 12 12 35 PP Fixed cable 4xB (4 mm) Pt platinized 5...70 5...70 1...100000 μS/cm Pt1000 6.0914.040 125 12 12 35 Steel, stainless Fixed cable 4xB (4 mm) Steel, stainless 0...70 0...70 0...300 μS/cm Pt1000 6.0915.100 125 12 12 34 PEEK Fixed cable, plug N 5-ring, Pt 0...70 0...70 5...20000 μS/cm Pt1000 (ideal) 6.0915.130 142 12 12 50 PEEK Fixed cable, plug N 5-ring, Pt 0...70 0...70 5...100000 μS/cm Pt1000 (ideal) 6.0916.040 125 12 12 35 Steel, stainless Fixed cable, plug N Steel, stainless 0...70 0...70 0...300 μS/cm Pt1000 6.0917.080 125 12 12 30 PEEK Fixed cable, plug O 4-wire, Pt 0...70 0...70 0.015…250 mS/cm Pt1000 6.0918.040 125 12 12 35 Steel, stainless Fixed cable, plug O Steel, stainless 0...70 0...70 0…300 uS/cm Pt1000 6.0919.140 125 12 12 40 Glass Fixed cable, plug O 3-ring, Pt 0...70 0...70 0.1…1000 mS/cm Pt1000 6.0920.100 125 12 12 34 PEEK Fixed cable, plug N 5-ring, Pt 0...70 0...70 5…20000 uS/cm Pt1000 6.0920.130 142 12 12 50 PEEK Fixed cable, plug N 5-ring, Pt 0...70 0...70 5 …. 100000 uS/cm Pt1000 6.1103.000 121 12 5 20 Glass Fixed cable -50...100 -50...100 -50...100 °C Pt100 6.1110.010 120 12 5 20 Glass Fixed cable 2xB (2 mm) -50...180 -50...180 -50...180 °C Pt1000 6.1110.100 125 12 5 20 Glass G -50...180 -50...180 -50...180 °C Pt1000 6.1110.110 178 12 6.4 20 Glass G -50...180 -50...180 -50...180 °C Pt1000 6.1111.120 90 12 5 20 Glass G -50...180 -50...180 -50...180 °C Pt1000 6.1114.010 140 12 3 10 PEEK Fixed cable, plug 2x2 B Steel, stainless -50...100 -50...100 -50...100 °C Pt1000 6.1115.000 135 12 12 30 Glass Fixed cable 0...40 0...40 129 odes ange short-term ange long-term (°C) ., RDE., RRDE.) e r e r atur atur oelectr RDE/RRDE tips/ micr (6.12, PT Length (mm) Shaft diameter (mm) Shaft material Disk diameter (mm) Disk material Ring width (mm) Ring material Gap between ring and disk (mm) Connector Temper (°C) Temper 6.1204.130 52.5 7 PEEK 2 Ag M3 0…40°C 0…40°C 6.1204.140 52.5 7 PEEK 2 Au M3 0…40°C 0…40°C 6.1204.170 52.5 7 PEEK 3 Pt M3 0…40°C 0…40°C 6.1204.190 52.5 7 PEEK 2 Pt M3 0…40°C 0…40°C 6.1204.300 52.5 10 PEEK 3 GC M4 0…40°C 0…40°C 6.1204.310 52.5 10 PEEK 3 Pt M4 0…40°C 0…40°C 6.1204.320 52.5 10 PEEK 3 Au M4 0…40°C 0…40°C 6.1204.330 52.5 10 PEEK 3 Ag M4 0…40°C 0…40°C 6.1204.600 52.5 8 Glass 2 GC M3 0…50°C 0…50°C 6.1204.610 52.5 8 Glass 1 Pt M3 0…50°C 0…50°C AG.100 52 2 Glass 0.1 Ag B (2 mm, male) 0…40°C 0…40°C AG.25 52 2 Glass 0.025 Au B (2 mm, male) 0…40°C 0…40°C AG.30 52 2 Glass 0.03 Ag B (2 mm, male) 0…40°C 0…40°C AG.300 52 2 Glass 0.3 Ag B (2 mm, male) 0…40°C 0…40°C AU.10 52 2 Glass 0.01 Au B (2 mm, male) 0…40°C 0…40°C AU.100 52 2 Glass 0.1 Au B (2 mm, male) 0…40°C 0…40°C AU.200 52 2 Glass 0.2 Au B (2 mm, male) 0…40°C 0…40°C AU.25 52 2 Glass 0.025 Au B (2 mm, male) 0…40°C 0…40°C AU.300 52 2 Glass 0.3 Au B (2 mm, male) 0…40°C 0…40°C AU.40 52 2 Glass 0.04 Au B (2 mm, male) 0…40°C 0…40°C AU.50 52 2 Glass 0.05 Au B (2 mm, male) 0…40°C 0…40°C AU.500 52 2 Glass 0.5 Au B (2 mm, male) 0…40°C 0…40°C IR.75 52 2 Glass 0.075 Ir B (2 mm, male) 0…40°C 0…40°C PD.100 52 2 Glass 0.1 Pd B (2 mm, male) 0…40°C 0…40°C PD.25 52 2 Glass 0.025 Pd B (2 mm, male) 0…40°C 0…40°C PD.300 52 2 Glass 0.3 Pd B (2 mm, male) 0…40°C 0…40°C PD.500 52 2 Glass 0.5 Pd B (2 mm, male) 0…40°C 0…40°C PT.10 52 2 Glass 0.01 Pt B (2 mm, male) 0…40°C 0…40°C PT.100 52 2 Glass 0.1 Pt B (2 mm, male) 0…40°C 0…40°C PT.1000 52 2 Glass 1 Pt B (2 mm, male) 0…40°C 0…40°C PT.20 52 2 Glass 0.02 Pt B (2 mm, male) 0…40°C 0…40°C PT.200 52 2 Glass 0.2 Pt B (2 mm, male) 0…40°C 0…40°C PT.25 52 2 Glass 0.025 Pt B (2 mm, male) 0…40°C 0…40°C PT.300 52 2 Glass 0.3 Pt B (2 mm, male) 0…40°C 0…40°C PT.50 52 2 Glass 0.05 Pt B (2 mm, male) 0…40°C 0…40°C PT.500 52 2 Glass 0.5 Pt B (2 mm, male) 0…40°C 0…40°C RDE.AG50 52.5 10 PEEK 5 Ag M4 0…40°C 0…40°C RDE.AU50 52.5 10 PEEK 5 Au M4 0…40°C 0…40°C RDE.BLANK 52.5 10 PEEK 5 Empty M4 0…40°C 0…40°C RDE.CU50 52.5 10 PEEK 5 Cu M4 0…40°C 0…40°C RDE.GC50 52.5 10 PEEK 5 GC M4 0…40°C 0…40°C RDE.PT50 52.5 10 PEEK 5 Pt M4 0…40°C 0…40°C RDE.STEEL 52.5 10 PEEK 5 Stainless steel M4 0…40°C 0…40°C RDE.ZN50 52.5 10 PEEK 5 Zn M4 0…40°C 0…40°C RRDE.AUPT 51.5 11.5 PEEK 5 Au 0.375 Pt 0.375 M4 0…40°C 0…40°C RRDE.GCPT 51.5 11.5 PEEK 5 GC 0.375 Pt 0.375 M4 0…40°C 0…40°C RRDE.PTPT 51.5 11.5 PEEK 5 Pt 0.375 Pt 0.375 M4 0…40°C 0…40°C Technical specifications o- ation 130 odes and digitated odes/micr odes ate size (mm) ate material een-printed UX material Scr electr inter electr electr WE material WE dimension (mm) A Cell configur Substr Substr Units/box 110 Carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 75 units C110 Carbon d. 4 Carbon Work in solution 34 x 10 x 0.5 Ceramic 75 units C11L Carbon d. 4 Carbon Work in solution 34 x 10 x 0.5 Ceramic 75 units 150 Carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 75 units 220AT Gold AT d. 4 Platinum Standard 34 x 10 x 0.5 Ceramic 75 units 220BT Gold BT d. 4 Gold BT Standard 34 x 10 x 0.5 Ceramic 75 units C220AT Gold AT d. 4 Gold AT Work in solution 34 x 10 x 0.5 Ceramic 75 units C220BT Gold BT d. 1.6 Gold BT Work in solution 34 x 10 x 0.5 Ceramic 75 units C223AT Gold AT d. 1.6 Gold AT 1.6 d 34 x 10 x 0.5 Ceramic 75 units C223BT Gold BT d. 4 Gold BT 1.6 d 34 x 10 x 0.5 Ceramic 75 units 250AT Gold AT d. 4 Platinum Standard 34 x 10 x 0.5 Ceramic 75 units 250BT Gold BT d. 4 Platinum Standard 34 x 10 x 0.5 Ceramic 75 units 410 Co-phthalocyanine/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 75 units 550 Platinum d. 4 Platinum Standard 34 x 10 x 0.5 Ceramic 75 units 550BT Platinum BT d. 4 Platinum BT Standard 34 x 10 x 0.5 Ceramic 75 units C550 Platinum d. 4 Carbon Work in solution 34 x 10 x 0.5 Ceramic 75 units 610 Meldolaś blue/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 75 units 710 Prussian blue/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 75 units F10 Ferrocyanide/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 75 units 810 Ruthenium oxide d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 910 Palladium d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 010 Silver d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 75 units C013 Silver d. 1.6 Carbon 1.6 d 34 x 10 x 0.5 Ceramic 75 units 110AGNP Silver nanoparticles/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110BI Bismuth oxide/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110CNF Carbon nanofibres/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units Carbon nanofibres-gold 110CNF-GNP d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units Nanoparticles/carbon 110CNT Multi-walled carbon nanotubes/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units Multi-walled carbon 110CNT-GNP d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units Nanotubes-gold nanoparticles/carbon 110CSQD Core-shell quantum dots d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units ZnS/CdSe/carbon 110GNP Gold nanoparticles/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units Streptavidin modified gold 110GNP-STR d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units Nanostructured/carbon 110GPH Graphene/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110GPH-GNP Graphene-gold nanoparticles/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110GPHOX Graphene oxide/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110MC Mesoporous carbon/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110NI Nickel oxide/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110OMC Ordered mesoporous carbon/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110PANI Polyaniline/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110QD Core quantum dots CdSe/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110RGPHOX Reduced graphene oxide/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 110STR Streptavidin/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units Single-walled carbon nanotubes/ 110SWCNT d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units Carbon 110XTR Extravidin/carbon d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units 4W110 Carbon d. 2.95 Carbon 4WE sharing AUX and REF 38 x 20 x 1.0 Ceramic 20 units 8W110 Carbon d. 2.95 Carbon 8WE sharing AUX and REF 38 x 20 x 1.0 Ceramic 20 units 8X110 Carbon d. 2.56 Carbon Array of 8X ectrochemical cells 34 x 79 x 1.0 Ceramic 20 units 8X110STR Streptavidin/Carbon d. 2.95 Carbon Array of 8X ectrochemical cells 34 x 79 x 1.0 Ceramic 10 units 8X220AT Gold AT d. 2.56 Gold Array of 8X ectrochemical cells 34 x 79 x 1.0 Ceramic 20 units 8X550 Platinum d. 2.56 Gold AT Array of 8X ectrochemical cells 34 x 79 x 1.0 Ceramic 20 units 96X110 Carbon d. 3 Carbon ELISA 96X electrochemical cells 74 x 110 x 5.0 PCB 4 plates 96X110CNT Multi-walled carbon nanotubes/carbon d. 3 Carbon ELISA 96X electrochemical cells 74 x 110 x 5.0 PCB 2 plates o- ation 131 odes and digitated odes/micr odes ate size (mm) ate material een-printed UX material Scr electr inter electr electr WE material WE dimension (mm) A Cell configur Substr Substr Units/box Multi-walled carbon 96X110CNT-GNP d. 3 Carbon ELISA 96X electrochemical cells 74 x 110 x 5.0 PCB 2 plates Nanotubes-gold nanoparticles/carbon 96X110GNP Gold nanoparticles/carbon d. 3 Carbon ELISA 96X electrochemical cells 74 x 110 x 5.0 PCB 2 plates Streptavidin modified gold 96X110GNP-STR d. 3 Carbon ELISA 96X electrochemical cells 74 x 110 x 5.0 PCB 2 plates Nanostructured/carbon 96X110STR Streptavidin/carbon d. 3 Carbon ELISA 96X electrochemical cells 74 x 110 x 5.0 PCB 2 plates 96X110SWCNT Single-walled carbon nanotubes/carbon d. 3 Carbon ELISA 96X electrochemical cells 74 x 110 x 5.0 PCB 2 plates 96X110XTR Extravidin/carbon d. 3 Carbon ELISA 96X electrochemical cells 74 x 110 x 5.0 PCB 2 plates 96X220 Gold d. 3 Gold ELISA 96X electrochemical cells 74 x 110 x 5.0 PCB 4 plates 96X550 Platinum d. 3 Platinum ELISA 96X electrochemical cells 74 x 110 x 5.0 PCB 4 plates X1110 Carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 75 units X4410 Co-phthalocyanine/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 75 units XFF10 Ferrocyanide/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 75 units X1110AGNP Silver nanoparticles/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110BI Bismuth oxide/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110CNF Carbon nanofibres/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units Carbon nanofibres-gold X1110CNF-GNP d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units Nanoparticles/carbon X1110CNT Multi-walled carbon nanotubes/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units Multi-walled carbon nanotubes- X1110CNT-GNP d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units Gold nanoparticles/carbon Core-shell quantum dots X1110CSQD d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units ZnS/CdSe/carbon X1110GNP Gold nanoparticles/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units Streptavidin modified X1110GNP-STR d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units Gold nanostructured/carbon X1110GPH Graphene/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110GPH-GNP Graphene-gold nanoparticles/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110GPHOX Graphene oxide/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110MC Mesoporous carbon/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110NI Nickel oxide/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110OMC Ordered mesoporous carbon/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110PANI Polyaniline/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110QD Core quantum dots CdSe/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110RGPHOX Reduced graphene Oxide/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110STR Streptavidin/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110SWCNT Single-walled carbon nanotubes/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units X1110XTR Extravidin/carbon d. 4 Carbon 2WE sharing AUX and REF 34 x 10 x 0.5 Ceramic 50 units GLU10 Glucose d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units LACT10 Lactate d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units UA10 Uric Acid d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 50 units Transparent ITO10 ITO d. 4 Carbon Standard 34 x 10 x 0.5 20 units Plastic Transparent P10 PEDOT d. 4 Carbon Standard 34 x 10 x 0.5 75 units Plastic Transparent AUTR10 Transparent Gold d. 4 Carbon Standard 34 x 10 x 0.5 20 units Plastic Transparent COTE10 Transparent Carbon d. 4 Carbon Standard 34 x 10 x 0.5 20 units Plastic AL10 Aluminium d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units Transparent BIOFV1 PEDOT d. 4 Carbon Standard 34 x 10 x 0.5 75 units Plastic BDD10 Boron doped diamond d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units CBDD10 Boron doped diamond d. 4 Carbon Work in solution 34 x 10 x 0.5 Ceramic 20 units BI10 Bismuth d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units CR10 Chromium d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units CST10 Carbon Steel d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units CU10 Copper d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units Technical specifications 132 o- ation odes and digitated odes/micr odes ate size (mm) ate material een-printed UX material Scr electr inter electr electr WE material WE dimension (mm) A Cell configur Substr Substr Units/box MO10 Molybdenum d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units NI10 Nickel d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units PB10 Lead d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units SB10 Antimony d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units SN10 Tin d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units ST10 Steel d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units TA10 Tantalum d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units TI10 Titanium d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units W10 Tungsten d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 20 units PW-AU10 Gold d. 4 Carbon Standard 34 x 10 x 0.5 White Plastic 20 units TLFCL010-CIR Silver d. 4 Carbon Thin layer flow-cell incorporated 80 x 25 x 0.1 Ceramic 10 units TLFCL110 Carbon 12.6 mm2 Carbon Thin layer flow-cell incorporated 80 x 25 x 0.1 Ceramic 10 units TLFCL110-CIR Carbon d. 4 Carbon Thin layer flow-cell incorporated 80 x 25 x 0.1 Ceramic 10 units TLFCL110S Carbon 2 mm2 Carbon Thin layer flow-cell incorporated 80 x 25 x 0.1 Ceramic 10 units TLFCL1110 Carbon 2 mm2 x 2 Carbon Thin layer flow-cell incorporated 80 x 25 x 0.1 Ceramic 10 units TLFCL210AT-CIR Gold AT d. 4 Carbon Thin layer flow-cell incorporated 80 x 25 x 0.1 Ceramic 10 units TLFCL210BT-CIR Gold BT d. 4 Carbon Thin layer flow-cell incorporated 80 x 25 x 0.1 Ceramic 10 units 0.8 x 5 (external) TLFCL2222AT Gold AT Gold AT Thin layer flow-cell incorporated 80 x 25 x 0.1 Ceramic 10 units 0.4 x 5 (internal) TLFCL510-CIR Platinum d. 4 Carbon Thin layer flow-cell incorporated 80 x 25 x 0.1 Ceramic 10 units SPESMIX Mix: Carbon, gold, platinum d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 100 units Standard, 1.6 d and work in AUMIX Mix: Gold d.4 and d.1.6 Gold 34 x 10 x 0.5 Ceramic 100 units solution Mix: silver, gold BT, copper and SERSMIX d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 85 units silver-coated copper Mix: Co-phthalocyanine, meldolaś MEDIATORSPES d. 4 Carbon Standard 34 x 10 x 0.5 Ceramic 100 units blue,prussian blue, ferrocyanide/carbon Mix: ITO, PEDOT, transparent gold Transparent OTEMIX d. 4 Carbon Standard 34 x 10 x 0.5 40 units and transparent carbon plastic 10 microns G-IDE222 Gold Gold Interdigitated with AUX and REF 22 x 7.0 x 0.7 Glass 20 units lines and gaps 10 microns G-IDE555 Platinum Platinum Interdigitated with AUX and REF 22 x 7.0 x 0.7 Glass 20 units lines and gaps 5 microns lines G-IDEAG5 Silver Silver Interdigitated squared format 22 x 7.0 x 0.7 Glass 20 units and gaps 10 microns G-IDEAU10 Gold Gold Interdigitated squared format 22 x 7.0 x 0.7 Glass 20 units lines and gaps 5 microns G-IDEAU5 Gold Gold Interdigitated squared format 22 x 7.0 x 0.7 Glass 20 units lines and gaps 5 microns lines G-IDECU5 Copper Copper Interdigitated squared format 22 x 7.0 x 0.7 Glass 20 units and gaps 10 microns G-IDEPT10 Platinum Platinum Interdigitated squared format 22 x 7.0 x 0.7 Glass 20 units lines and gaps 5 microns G-IDEPT5 Platinum Platinum Interdigitated squared format 22 x 7.0 x 0.7 Glass 20 units lines and gaps 5 and 10 Mix: G-IDEMIX Mix: Gold, platinum microns lines gold, Interdigitated:concentric; squared 22 x 7.0 x 0.7 Glass 20 units and gaps platinum 10 microns G-IDECONAU10 Gold Gold Interdigitated concentric format 22 x 7.0 x 0.7 Glass 20 units lines and gaps 10 microns G-IDECONPT10 Platinum Platinum Interdigitated concentric format 22 x 7.0 x 0.7 Glass 20 units lines and gaps o- 133 ation odes and digitated odes/micr odes ate size (mm) ate material een-printed UX material Scr electr inter electr electr WE material WE dimension (mm) A Cell configur Substr Substr Units/box d. 3 / Interdigitated microelectrode G-MEA222 Gold Microholes Gold 22 x 7.0 x 0.7 Glass 20 units array d. 3mm 10 microns d. 3 / Interdigitated microelectrode G-MEA555 Platinum Microholes Platinum 22 x 7.0 x 0.7 Glass 20 units array d. 3mm 10 microns Microband 10 Interdigitated microelectrode G-MEAB222 Gold Gold 22 x 7.0 x 0.7 Glass 20 units microns array Microband 10 Interdigitated microelectrode G-MEAB555 Platinum Platinum 22 x 7.0 x 0.7 Glass 20 units microns array 200 microns IDEAU200 Gold Gold Interdigitated squared format 22 x 7.0 x 0.7 Ceramic 20 units lines and gaps 200 microns IDEAU200-HPT-WB Gold Gold Squared design / Pt heater 22 x 7.0 x 0.7 Ceramic 50 units lines and gaps 100 microns Transparent P-IDEAU100 Gold Gold Interdigitated squared format 22 x 7.0 x 0.7 50 units lines and gaps plastic 100 microns PW-IDEPD100 Palladium Palladim Interdigitated squared format 22 x 7.0 x 0.7 White plastic 50 units lines and gaps 100 microns PW-IDEAU100 Gold Gold Interdigitated squared format 22 x 7.0 x 0.7 White plastic 50 units lines and gaps www.metrohm.com witzerland G, CH-9100 Herisau, S ohm A , Printing Metr SW 10 Subject to change without notice. Design Ecknauer+Schoch A 8.000.5302EN – 2019-