6. AOACSPIFANMethods-2018Awards

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Joseph et al.: J ournal of AOAC I nternational V ol. 98, N o . 3, 2015  1123

the potassium dihydrogen phosphate and quantitatively transfer into a 1 L Schott bottle. Add a further 300 mL deionized water to the beaker to dissolve any remaining potassium dihydrogen phosphate, quantitatively transfer into the Schott bottle, make up to 1 L. Cap, mix, and adjust the pH to 2.3 ± 0.1 with concentrated phosphoric acid. Store at room temperature. ( i )  0.1 M sodium hydrogen carbonate (1000 mL) .—Weigh 8.40 g sodium hydrogen carbonate into a 500 mL beaker. Add 300 mL deionized water to dissolve the sodium hydrogen carbonate and quantitatively transfer into a 1 L Schott bottle. Add a further 300 mL deionized water to the beaker to dissolve any remaining sodium hydrogen carbonate, quantitatively transfer into the Schott bottle, make up to 1 L, cap, and mix to ensure full solubility. Store at room temperature. ( j )  AG 1-X8 anion exchange resin .—Before use, soak the AG 1-X8 anion exchange resin in deionized water for 18–24 h, and store in deionized water until use. Store in a refrigerator. ( k )  HPLC mobile phase A: 10 mM ammonium acetate in water (1000 mL) .—Weigh 0.77 g ammonium acetate into a 1 L Schott bottle, followed by 1000 mL deionized water. Cap and mix to ensure full solubility. Store at room temperature. ( l )  HPLC mobile phase B: 10 mM ammonium acetate in 97% acetonitrile (1000 mL) .—Weigh 0.77 g ammonium acetate into a 50 mL beaker. Use 30 mL deionized water to quantitatively transfer to a 1 L Schott bottle. Stir to fully dissolve and add 970 mL acetonitrile. Sonicate for 10 min to ensure full solubility. Store at room temperature.

the pellets have dissolved, allow the solution to cool and then transfer quantitatively through a glass funnel into a 2000 mL measuring cylinder and bring to volume with deionized water. Store at room temperature. ( d )  20 mg/mL 3-nitroaniline (100 mL) .—( Caution : Wear gloves when working with this chemical.) Weigh 2.0 g aliquots of 3-nitroaniline into 100 mL Schott bottles and cap tightly. Store at room temperature. To one preweighed bottle of 3-nitroaniline add 100 mL acetonitrile using a graduated measuring cylinder. This is sufficient for two batches of 36 sample tubes. Prepare fresh daily. (e)  100 mg/mL EDAC (25 mL) .—( Caution : Exposure to moisture degrades this reagent.) Preweigh 2.5 g aliquots of EDAC into 50 mL polypropylene tubes and cap tightly. Store in a freezer at or below –10°C in a desiccated container. To one preweighed tube of EDAC add 25 mL deionized water. Prepare fresh daily. ( f )  TBME–n-hexane (70 + 30, v/v; 2000 mL) .—Measure 1400 mL TBME into a 2000 mL Schott bottle and add 600 mL n -hexane. Cap and mix. Store at room temperature. ( g )  Sulfuric acid in water (25%, v/v; 2000 mL) .—( Caution : Preparation of solution should be performed inside a fume cupboard.) Add approximately 1200 mL deionized water to a 2 L volumetric flask followed by slow addition of 500 mL sulfuric acid. Mix and allow to cool to room temperature. Bring to 2 L volume and store in a Schott bottle. Store at room temperature. ( h )  0.05 M potassium dihydrogen phosphate, pH 2.3 (1000 mL) .—Weigh 6.80 g potassium dihydrogen phosphate into a 500 mL beaker. Add 300 mL deionized water to dissolve

Figure 2015.02B. Chromatograms of confirmation ion for recovery 1 (matrix blank; top), recovery 2 (0.1 µg/kg, ≈LOQ; middle), and recovery 4 (1.0 µg/kg, LOR; bottom).