AOAC SPIFAN ERP Meeting Book-March 16, 2016

Additional data on Multi-Laboratory Validation – Vitamin C method AOAC First Action 2012.22 / F. Martin, NRC/AS

23.Nov.2015

MLT code

Bottle #

Conc (mg/100g)

12.7 12.6 10.6 10.5 14.9 15.1 11.6 11.6

1

XKIP216

2

1

HYJU890

2

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 XKIP216 XKIP216 XKIP216 XKIP216 HYJU890 HYJU890 HYJU890 HYJU890

Bottle #

Conc (mg/100g)

14.5 14.9 11.4 11.7 14.9 14.8 13.7 13.7

1 1 2 2 1 1 2 2

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.

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