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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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R E S U L T S A N D C O N C L U S I O N
Participation to MLT
From the 12 laboratories that initially initially accepted to participate, two of them did not receive
the MLT samples due to customs restrictions. The remaining 10 laboratories reported valid data.
Results
Summarized results of the additional MLT set of samples can be found in the table below. Full set of
data is given in Annex B
.
Requirements (SMPR 2012.012)
≤ 5 % ≤ 10 %
Sample
n
Mean
(mg/100 g RTF)
RSD
r
(%)
RSD
R
(%)
HorRat
Adult Nutritional Powder Low Fat
10
17.6
1.5
6.5
0.88
Infant Formula RTF Milk Based
10
12.0
10.7
13.2
1.70
n = number of laboratories (after outliers removal)
RSD
r
: relative standard deviation of repeatability
RSD
R
: relative standard deviation of reproducibility
The results for the Adult Nutritional Powder Low Fat product are now well within the SMPR
requirements. The repeatability went down from 31.8 % for the first round to 1.5 % in the present
study, whereas the reproducibility went down from 33.0 % to 6.5 %. The hypothesis that during the
first round the high precision data came from either homogeneity of the sample itself, storage
spoilage or can mislabelling seems to be confirmed.
Regarding the Infant Formula RTF Milk Based, even if the precision numbers improved (repeatability
down from 25.6 % to 10.7 %, reproducibility from 30.6 % to 13.2 %), they remained slightly outside
of the requirements.
One of the participant laboratories analysed duplicate samples the four bottles they received. The
data are presented in the table below:
AOAC OMB Meeting Book
378