420 / 435
(g).
TCA —
Merck, or equivalent.
28
(h).
TCEP.—
Fluka, or equivalent.
29
(i).
Isoascorbic acid.—
Fluka, or equivalent.
30
(j).
Orotic acid.-
Sigma, or equivalent
.
31
D.
Preparation of Solutions
32
(a).
Sodium acetate solution 500 mmol/L (pH 5.4).
— Into a 500 mL volumetric flask,
33
weigh 34.0 g sodium acetate trihydrate, add about 400 mL of water and dissolve
34
well. Adjust pH to 5.4 with phosphoric acid 85 % and make up to volume with
35
water.
36
(b).
TCA (15 %) .—
Into a 500 mL volumetric flask, weigh 75.0 g of TCA, dissolve
37
and make up to volume with water
38
(c).
TCEP (250 µg/mL).—
Into a 500 mL volumetric flask, weigh 125 mg of TCEP,
39
dissolve and make up to volume with water.
40
(d).
Mobile phase for UHPLC.-
Into a 250 mL flask, mix 0.4 g decylamine, 2.5 mL
41
acetonitrile, 25 mL sodium acetate solution 500 mmol/L (pH 5.4) and 205 mL of
42
water. No making up to volume is preferred. Adjust pH to 5.4 with phosphoric
43
acid 85 %. Add 10 mg TCEP.
44
E.
Preparation of Standards
45
(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
48
volumetric flask, weigh 12.5 mg ascorbic acid. Dissolve and make up to
49
volume with TCEP solution. This solution can be kept for 3 months if stored at
50
4 °C away from light.
51
AOAC 2012.22 (FINAL VERSION REVIEW) - JUNE 2016
FOR ERP USE ONLY
DO NOT DISTRIBUTE
AOAC OMB Meeting Book
391