AOAC SPIFAN ERP Meeting Book (3-16-16)

AOAC FIRST ACTION 2012.22

MULTI LABORATORY TESTING

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Analysis

a. Chromatographic conditions

i. Injection volume, 5 µL

ii. Autosampler temperature: 10 °C

iii. Column temperature: 25 °C

iv. Flow rate, 0.35 mL/min

v. Run time, 4.0 minutes

vi. Mobile phase for LC, see (D.d)

Note

At the end of each analytical series, rinse column with 50% acetonitrile:water for 10

minutes at 0.4 mL/min

System suitability test

.- Equilibrate the chromatographic system for ≥ 0.5 h. Inject a

working standard solution at least 6 times and check peak retention times and

response (peak height or area). Inject working standard solutions on a regular basis

within a series of analyses.

Calibration

.- Make single injections of each of the working standard solutions at least

at the beginning and the end of each analytical series. Establish the calibration

curve (7-point) by plotting peak response (height or area) vs ascorbic acid

concentration. Calculate the linear regression parameters. Calculate slope (S) and

intercept (I).

Analysis

.- Make single injections of sample solutions.

Identification

.- Identify ascorbic acid peak in the chromatograms of the sample

solutions by comparison with the retention time and UV spectrum of the

corresponding peak in the standard solution (see example chromatograms in H).

Calculations

Calculate the concentration of vitamin C, in mg ascorbic acid/100 g expressed in product “as is”

for liquid products or as “reconstituted powder” for powder samples, as follows:

1000 x

x Vm x S

100 x

x V x V I)- (A C



Where:

A = response (height or area) of the ascorbic acid peak obtained for the sample solution

I = intercept of the calibration curve

S = slope of the calibration curve

m = weight of the test portion, in g (2.0 g)

= volume of the test solution (volume used to dissolve the test portion) in mL (10 mL)

= volume used in the sample dilution (1.0 mL)

= volume of the final sample dilution (10 mL)

100 = conversion to 100 g basis

1000 = conversion from μg to mg.

Note: if results expressed in powder sample are needed, use the reconstitution rate

to calculate (c*225 g/25 g).

2012.22/VitC-03 (February 2016) - MLT

FOR ERP USE ONLY

DO NOT DISTRIBUTE