AOAC OMB Final Action Recommendation (December 2019)-2016.14

2016.14 (Jan. 2019) FOS-03 MLT Report FOR ERP USE ONLY DO NOT DISTRIBUTE

(n) Analytical column. —CarboPac PA20 (150 x 3 mm, 6.5 µm) with no guard, or CarboPac PA1 (250 x 2 mm, 10 µm), with PA1 guard (50 x 2 mm, 10 µm) (Thermo Fisher Scientific, MA USA), or equivalent. (o) Metal free liquid chromatograph consisting of : - Quaternary gradient pump able to deliver a flow of 0.5 mL/min (PA20) or 0.25 mL/min (PA1). - Helium degassing system. - Autosampler (cooling system recommended) able to inject 25 µL (PA20) or 20 µL (PA1). - Column compartment able to maintain a temperature of 30 °C (PA20) or 20 °C (PA1). - Electrochemical detector working in pulsed amperometric detection mode, equipped with a gold working electrode and an Ag/AgCl reference electrode (or equivalent). - Isocratic pump for post-column delivery, with pulse dampener, 125-µL reaction coil (or equivalent) and T-piece. - Data acquisition system. (c) Acetonitrile .—Gradient grade for liquid chromatography. (d) Acetic acid .—Glacial 100 % anhydrous, GR for analysis. (e) Potassium cyanohexaferrate(II)trihydrate .—[Optional]. (f) Zinc acetate .—[Optional]. (g) Trifluoroacetic acid (TFA) .—99 %. (h) Hydrochloric acid .—1 M . (i) Sodium acetate .—Anhydrous, ≥99.0 % (Only when using PA1 column for HPAEC- PAD). (j) Sodium hydroxide .—50 % ( w/w ). Carbonate is a divalent anion at pH ≥ 12 and binds strongly to the analytical column. It causes decrease of column selectivity and reduction of resolution and efficiency. To keep the concentrated NaOH solution carbonate free and avoid production of carbonate, several precautions should be taken: - The bottle should be handled with care to keep the precipitated carbonate at the bottom (do not shake or stir before use). - The solution should never be poured from the bottle. - Only plastic pipettes should be used. Chemicals and Standards (a) Deionised Water. —Purified with resistivity ≥18 MΩ . (b) Maleic acid. —Puriss., ≥ 99.0 %.

C.