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Additional data on Multi-Laboratory Validation – Vitamin C method AOAC First
Action 2012.22 / F. Martin, NRC/AS
23.Nov.2015
CONFIDENTIAL
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MLT code
Bottle #
Conc (mg/100g)
XKIP216
1
12.7
12.6
2
10.6
10.5
HYJU890
1
14.9
15.1
2
11.6
11.6
While the duplicates from the same bottle present excellent CV (from 0.1 % to 0.9%). The range of
concentration spans from 10.5 to 15.1 mg/100 g. It can indicate that the high precision data
obtained for the Infant Formula RTF is due to the variability within the samples and not on the
method.
To confirm these findings, it was decided to analyse samples at NRC, in duplicates, using a different
method (AOAC Official method 985.33). This method is based on a different chemical approach: the
reduction of the dye 2,6-dichlorophenolindophenol (DCPIP) by ascorbic acid. The results obtained
can be found in the table below:
MLT code
Bottle #
Conc (mg/100g)
XKIP216
1
14.5
XKIP216
1
14.9
XKIP216
2
11.4
XKIP216
2
11.7
HYJU890
1
14.9
HYJU890
1
14.8
HYJU890
2
13.7
HYJU890
2
13.7
For these samples the range of concentrations spans from 11.4 to 14.9 mg/100 gr.
Both tables tend to indicate that the high precision data collected during this additional MLT could
come from the variability of the samples, and not from the method AOAC 2012.22. Moreover this
variability has been observed using two distinct analytical methodologies.