Application Work AW IC ES6-0007-082017_G Sulfite determination in Cider by amperometric detection with Metrosep Carb 2 Branch Food, stimulants, beverages, flavors Keywords IC, DC, Amperometric detection, 930 858 Drinks, Food, Alcohols, Sulfite, Sulphite, Cider, Metrosep Carb 2-150/4.0, branch 7 Summary Sulfite IC Conductivity determination presents two difficulties: one is the chemical instability of this anion due to its nature and low peak resolution of chromatograms with sulfate analyte. Nevertheless, Sulfite anion has electrochemical activity that allows DC amperometric detection Reagents Due to sulfite chemical low stability in aqueous solution is necessary to stabilize samples and standards with a stability • Sodium hydroxide, puriss. 50 – 52% solution (e.g. Formaldehyde and NaOH) which produces a CAS 1310-73-2, Fluka 72064 Formaldehyde peak near sulfite retention time with DC • Sodium Acetate anhydrous >99,0 % CAS 127-09-3; amperometric detection. Sigma-Aldrich S2889 This AW describes the combination an IC high capacity • Formaldehyde solution ≥34.5 wt.% 15512 SIGMA-Column as Metrosep Carb 2 with NaOH- NaOAc (300mM-ALDRICH 300mM) eluent to improve peak resolution between sulfite • Sodium sulfite 71988 SIGMA BioUltra, anhydrous, and stability solution with DC amperometric detection. ≥98% (RT) Previous studies with lower columns capacity showed less • Soda lime p.a., with indicator, pellets; CAS 8006-28-8; peak resolution causing a slightly matrix effect on sample Sigma-Aldrich 72073 results. • Ultrapure water (UPW) resistivity >18.2 MΩ·cm (25 °C), Samples type I grade (ASTM D1193) from Flex 5 ELGA water Cider and sulfite spiked cider samples system Instruments Solutions 930 Compact IC pro 2.930.2460 Eluent Sodium Hydroxide 300.0 mmol.L-1 858 Professional Sample Processor 2.858.0020 Sodium Acetate 300.00 mmol.L-1 CO IC Amperometric Detector 2 free ultrapure water 2.850.9110 Rinsing Solution UPW : Methanol (1:1) IC equipment Wall-Jet cell: Carb (Au, Pd) 6.5337.010 Stablilization Formaldehyde 1.00 mmol.L-1l Metrosep Carb 2 150/4.0 6.1090.420 solution (SS) Sodium Hydroxide 0.20 mmol.L-1 Metrosep Carb 2 Guard 6.1090.500 MagIC Net™ 3.2 Professional 6.6059.322 Standard solutions IC equipment for ultrafiltration 6.5330.110 Sulfite anion solution from 0.5 to 50 mg.L-1 with stabilization Adsorbing tube, large and bent 6.1609.000 solution Sample preparation Samples prepared with stabilization solution Page 1 of 7 Application Work AW IC ES6-0007-082017_G Sulfite determination in Cider by amperometric detection with Metrosep Carb 2 Analysis Date Every solution was filtrated with 0.2 um inline ultrafiltration 04th Aug 2017 previously to injection Authors Eluent Flow 0.5 mL.min-1 Maria Aguirre Detector Mode DC IC Specialist Gomensoro S.A. E(V) 150 mV Javier Espuelas Range AUTO Lab Manager / IC Specialist Gomensoro S.A. DAMPING OFF DETECTOR TEMP 35 ºC Range 200 μA Channel measurement Current (nA) Col. Oven temperature 35 °C Sample Loop 20 uL Calculation Automatic integration using peak areas evaluated with MagIC NetTM 3.2 Results See appendix with chromatograms below Comments Other studies showed DC amperometry as a good solution for Sulphite determination. To improve peak resolution between the stability solution and the analyte is always a key point because of the possibility of a slightly sample matrix effect. In the present AW, the combination a very high capacity Column as Metrosep Carb 2 with the eluent NaOH-NaOAc (300mM-300mM) reveled an important improvement of peak resolution between Formaldehyde and Sulfite, reducing sample matrix effect. Is important to note, as existing AWs about amperometric detection revealed, the combination of high concentration NaOH (300 mM) eluent with the Metrosep Carb 2 column showed high stability of retention times of analytes almost for 4-5 days working with the same eluent bottle. Using of degassed water and plastic bottle (HDPE) for eluent are necessary to achieve optimum eluent stability results References [1] AW IC CH6-1089-032012 - Determination of sulfite using the Amperometric Detector with the DC Mode and two different stabilization solutions [2] AN-S-225 Sulfite in the presence of standard anions in beer on the column Metrosep A Supp 10 - 100/4.0 [3] Determination of Lactose in Lactose-free Yogurt, with Pulsed Amperometric Detection Ion Chromatography (PAD-IC). AW IC ES6-0003-092013_G Gomensoro IC team SPAIN Page 2 of 7 Application Work AW IC ES6-0007-082017_G Sulfite determination in Cider by amperometric detection with Metrosep Carb 2 Appendix Example Calibration Chromatograms for 20 uL injection volume Fig 1. 20 uL injection of sulfite standard 500 ug.L-1 Fig 2. 20 uL injection of sulfite standard 10 mg.L-1 Page 3 of 7 Application Work AW IC ES6-0007-082017_G Sulfite determination in Cider by amperometric detection with Metrosep Carb 2 Fig 3. Overlay of Chromatograms of Sulfite standards Fig 4. Calibration curve for sulfite standards (0.5 – 50 mg.L-1) Page 4 of 7 Application Work AW IC ES6-0007-082017_G Sulfite determination in Cider by amperometric detection with Metrosep Carb 2 Sample Chromatograms for 20 uL injection volume Fig 5 Overlay of Blank sample and Blank sample spiked with sulfite (stabilization solution) Fig 6. Cider Sample with Formaldehyde – Sodium Hydroxide stabilization solution Page 5 of 7 Application Work AW IC ES6-0007-082017_G Sulfite determination in Cider by amperometric detection with Metrosep Carb 2 Fig 7. Overlay of Cider sample and Cider sample sulfite spiked with 20 mg.L-1 with stabilization solution Fig 8. Magnified Overlay of Cider sample and Cider sample sulfite spiked with 20 mg.L-1 with stabilization solution Page 6 of 7 Application Work AW IC ES6-0007-082017_G Sulfite determination in Cider by amperometric detection with Metrosep Carb 2 Sample Results for 20 uL of injection Fig 9. Table with results of Cider Sample and Cider sulfite spiked Sample Page 7 of 7