ASTM D664 – Acid number More efficient with revised ASTM D664 Acid number determination 02 The acid number (AN) is a sum parameter for acidic com-vessel and a toluene-isopropanol(IPA)-water solvent pounds in petroleum products. The AN is crucial to mixture is added. The sample is then titrated with assure the quality of petroleum products and is an impor-c(KOH in IPA) = 0.1 mol/L until after the equivalence tant parameter in corrosion control. point. After the titration, the electrode and buret tip are rinsed first with the solvent mixture, followed by IPA, The AN according to D664 is determined by potentio-and then dist. H O. To rehydrate the membrane, the 2 metric titration. An appropriate amount of well-mixed electrode is placed for 3 to 5 min in dist. H O. Before 2 sample (see table 1 below) is weighed into a titration the next determination, the electrode is rinsed with IPA. Table 1. Sample size in dependency of the expected AN and solvent amount Sample weight/[g] Sample weight/[g] Expected acid number Solvent = 125 mL Solvent = 60 mL 0.05 – <1.0 20.0 ± 2.0 10.0 ± 1.0 1.0 – <5.0 5.0 ± 0.5 2.5 ± 0.25 5 – <20 1.0 ± 0.1 0.5 ± 0.05 20 – <100 0.25 ± 0.02 0.25 ± 0.02 100 – <260 0.1 ± 0.01 0.1 ± 0.01 New ASTM D664 – more cost-efficient While previous ASTM D664 required 125 mL solvent mixture per sample, the new version of ASTM D664 now offers the possibility to work with only 60 mL. This con-siderable reduction is not only a step towards green chemistry, it further reduces the costs and increases the analysis throughput. Reduce cost and make your chemistry green Save almost 50% of your solvent and save 50% of your money and save the environment. Increased productivity For automated systems, the lower amount of solvents allows the use of smaller beakers (e.g., 120 mL beakers). The rack can thus house more beakers and so the un-attended running time of the system prolongs which further reduces cost per sample. OMNIS – even more efficient OMNIS is Metrohm’s new, fully integrated titration sys-We measured the total analysis time for the acid num-03 tem that caters to the needs of today’s laboratories. The ber (AN) determination of 28 motor oil samples on an OMNIS Sample Robot provides space for up to 4 work-OMNIS Sample Robot S and compared it to an equiva-stations at which you can carry out up to 4 determina-lent system with a turntable autosampler. The OMNIS tions simultaneously – fully automated. Once the sam-Sample Robot S is equipped with 2 workstations and ples have been processed on your OMNIS Sample Robot, the determinations were carried out on the two work-they can be exchanged for new samples at any time – stations in parallel. Table 2 shows the total analysis even during ongoing operation. times for the two systems. To learn more about the advantage of automating the acid number (AN) determination with an OMNIS system watch the available video. Table 2. Results of the comparison System Sample Robot S/OMNIS Classical turntable autosampler Total analysis time 4 h 14 min 6 h 23 min Metrohm the reliable partner As an analytical instrument manufacturer, we frequently gaseous fuels (D03); aromatic, industrial, specialty, and encounter customers who face very similar issues in their related chemicals (D16); and water (D19). daily work. This firsthand knowledge uniquely positions us to identify broader industry problems and work Our work with industry partners at ASTM has allowed through the ASTM International process to develop clear us to pioneer novel applications, including the use of and concise standards that address those problems. thermometric titration for the analysis of acid number in petroleum products (ASTM D8045) and the use of We are actively involved in numerous committees that combustion ion chromatography for determining total touch many industries, from environmental to refining, fluorine, chlorine, and sulfur in liquefied petroleum gas with the largest contributions made in committees on (ASTM D7994). petroleum products, liquid fuels, and lubricants (D02); Literature [1] ASTM D664-17, Standard test method for acid number of petroleum products by potentiometric titration. [2] Metrohm Application Bulletin AB-404, Determination of the total acid number in petroleum products. [3] Metrohm Application Note AN-T-179, Determination of the acid number according to ASTM D664 and the base number in fresh motor oil. [4] Collaborating to solve industry problems, ASTM Standardization News, July/August 2017 issue, p. 38–39. Ordering information 04 Possible OMNIS system for the parallel acid number determination according to the revised ASTM D664 Component Quantity Order number OMNIS Professional Titrator 1 2.1001.0310 OMNIS Dosing Module 3 2.1003.0010 OMNIS Rod Stirrer «Sample Robot» 2 2.1006.0010 Main module Pick&Place S 1 2.1010.0010 Pick&Place module 2 2.1014.0010 «Peristaltic» (4-channel) pump module 1 2.1016.0110 FEP tubing / M6 / 150 cm 4 6.1805.030 dSolvotrode 2 6.00203.300 Sample beaker (20×) PP 120 mL (P&P) 2 6.01400.200 Titration head 3×NS14 / 4 × 6.4 mm (P&P) 2 6.01403.030 Beaker adapter for OMNIS 120 mL PP sample beaker 4 6.01404.030 Stirring propeller 20 mm ETFE 2 6.01900.030 OMNIS sample rack 16 × 120 mL 2 6.02041.030 Digital measuring module 2 6.02100.010 Cable MDL PL/SO 0.5 m 1 6.02102.010 Cable MDL PL/SO 1 m 2 6.02102.020 Electrode cable plug-in head Q / plug P, 1.5 m 2 6.02104.310 Network cable, 2m 2 6.02107.010 Gripper fingers 42.8–65 mm 1 6.02601.010 OMNIS 20 mL cylinder unit 2 6.03001.210 OMNIS 50 mL cylinder unit 2 6.03001.250 OMNIS instruments license: 1 license 1 6.06002.010 OMNIS Stand-alone license 1 6.06003.010 witzerland G, CH-9100 Herisau, S www.metrohm.com ohm A , printed by Metr SW Subject to change without prior notice Layout by Ecknauer+Schoch A 8.000.5259EN – 2018-06