2016 OMB Summer Meeting

AOAC OMB Meeting Book

391

AOAC 2012.22 (FINAL VERSION REVIEW) - JUNE 2016 FOR ERP USE ONLY DO NOT DISTRIBUTE

(g). TCA — Merck, or equivalent.

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(h). TCEP.— Fluka, or equivalent.

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(i). Isoascorbic acid.— Fluka, or equivalent.

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(j). Orotic acid.- Sigma, or equivalent .

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D.

Preparation of Solutions

(a). Sodium acetate solution 500 mmol/L (pH 5.4). — Into a 500 mL volumetric flask,

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weigh 34.0 g sodium acetate trihydrate, add about 400 mL of water and dissolve

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well. Adjust pH to 5.4 with phosphoric acid 85 % and make up to volume with

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water.

(b). TCA (15 %) .— Into a 500 mL volumetric flask, weigh 75.0 g of TCA, dissolve

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and make up to volume with water

(c). TCEP (250 µg/mL).— Into a 500 mL volumetric flask, weigh 125 mg of TCEP,

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dissolve and make up to volume with water.

(d). Mobile phase for UHPLC.- Into a 250 mL flask, mix 0.4 g decylamine, 2.5 mL

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acetonitrile, 25 mL sodium acetate solution 500 mmol/L (pH 5.4) and 205 mL of

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water. No making up to volume is preferred. Adjust pH to 5.4 with phosphoric

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acid 85 %. Add 10 mg TCEP.

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E.

Preparation of Standards

(Note: Vitamin C is sensitive to light and oxygen, conduct operations under subdued light, or 46

use amber glassware. Keep all solutions away from direct light.) 47

(a). Ascorbic acid stock solution (500 µg/mL). — Into a 25 mL amber glass

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volumetric flask, weigh 12.5 mg ascorbic acid. Dissolve and make up to

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volume with TCEP solution. This solution can be kept for 3 months if stored at

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4 °C away from light.