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C
ampos
G
iménez
&
M
artin
:
J
ournal of
AOAC I
nternational
V
ol
.
100, N
o
.
1, 2017
143
the SMPR. Repeatability decreased from 31.8% in the part 2
to 1.5%, whereas reproducibility decreased from 33.0 to 6.5%;
both values well below requirements. For infant formula RTF
(milk-based), despite improved precision numbers (repeatability
went from 25.6 to 10.7%, whereas reproducibility went from
30.6 to 13.2%), these values remained outside of the SMPR.
The hypothesis that either sample spoilage (presumably of the
RTF) or can mislabeling (most likely the powder) took place
during the first round seemed to be confirmed.
One of the participants decided to analyze the four bottles
received in duplicate. To mirror this experiment, the decision
was made to also analyze the samples at the Nestlé Research
Center using a different method (AOAC
Official Method
SM
985.33
). Both sets of data (data not shown) confirmed that
the variability observed in the RTF sample came from sample
heterogeneity not the method. These data were presented to the
ERP in March 2016 and subsequently accepted.
Conclusions
The precision figures obtained during this collaborative study
show that Method
2012.22
complies with the requirements
set in the corresponding SMPR, and thus, that the method is
fit for purpose for the analysis of vitamin C (
l
-ascorbic acid)
in infant formula and adult/pediatric nutritionals. Both HPLC
(5) or UHPLC (6) conditions are of equivalent performance,
provided that suitability conditions are respected, thereby
allowing for method applicability in all laboratories. These data
were submitted to the ERP for review at the Mid-Year AOAC
Meeting annual meeting held in March 2016 in Gaithersburg,
MD. The ERP determined that the presented data met the SMPR
set by SPIFAN, and thus recommended the method be granted
Final Action status.
Acknowledgments
We especially thank Colleen Fehrenbach at Covance
Laboratories (Madison, WI) for dispatching samples to the
participants. We greatly thank the following participants
and their associates for their valuable contributions to the
study: Karen Schimpf and Linda Butler Thompson, Abbott
Laboratories (Columbus, OH); Dalal Aoude-Werner and Julie
Dalmas-Le Grandois, Aérial (Illkirch, France); Jeanette Wong
and Joanne Chia, ALS Global (Singapore); Isabelle Malaviole,
Laboratoire Aquanal (Pessac, France); Maggie Mapar, Tiffany
Nguyen, and Michael Hoard, Arizona Nutritional Supplements
(Chandler, AZ); George Joseph, Asure Quality (Auckland, New
Zealand); Lifu Ma, Certified Laboratories (Plainview, NY);
Bolong Wu, Chinese Academy of Inspection and Quarantine
(Beijing, People’s Republic of China); Tom Rogers and John
Austad, Covance Laboratories (Madison, WI); Bente Marianne
Jensen, Ina Pedersen, and Sabine Meng Jensen, Eurofins Steins
Laboratorium A/S (Vejen, Denmark); Yinghui Zhang and
Wenjuan Jobgen, Eurofins Scientific, Inc. (Des Moines, IA);
Table 2. Results of statistical analysis on original set of data
a
SMPR 2012.012
requirements
n
b
Avg.,
mg/100 g
≤5% ≤10%
HorRat
RSD
r
, % RSD
R
, %
Adult nutritional
RTF (high-fat)
c
21
17.6
4.2
11.3
1.5
SRM 1849a
d
17
8.1
3.5
3.7
0.5
Child formula
powder
19
4.9
2.6
4.5
0.5
Adult nutritional
powder (milk
protein-based)
19
6.3
1.4
3.2
0.4
Infant formula
powder
(soy-based)
17
10.3
1.6
6.0
0.8
Infant formula RTF
(milk-based)
19
3.5
25.6
e
30.6
e
3.3
e
Adult nutritional
powder (low-fat)
21
11.0
31.8
e
33.0
e
4.2
e
Adult nutritional
RTF (high-protein)
18
19.7
1.7
9.3
1.3
Infant elemental
powder
21
34.0
7.3
11.4
1.7
Infant formula
powder (partially
hydrolyzed,
soy-based)
22
19.5
2.4
8.0
1.1
a
Average, RSD
r
, RSD
R
, and HorRat values after removal of outliers.
b
n
represents the number of laboratories considered in the evaluation
(after removal of outliers). Twenty-two laboratories reported data.
c
RTF=Ready-to-feed.
d
SRM=Standard Reference Material.
e
Results suspected to be related to sample integrity.
See
Table 4 for
the final reproducibility results on these two matrixes.
Table 3. Full set of additional data on matrixes suspected
to be spoiled (liquid) or mislabeled (powder) in the original
testing
a
Lab
No.
Infant formula RTF
(milk-based)
b
Adult nutritional
powder (low-fat)
1
17.5
18.0
13.1
13.0
2
20.0
20.1
12.9
12.2
3
18.2
18.0
11.7
14.1
4
17.7
17.6
12.5
10.9
5
17.5
17.3
13.2
12.0
6
18.0
17.7
12.7
15.0
7
16.0
15.3
13.8
9.8
8
16.4
17.0
11.5
10.5
9
17.1
17.5
10.7
11.0
10
17.8
17.9
9.0
9.8
a
All results are in mg/100 g of reconstituted powder (25 g+200 g water)
or are as-is for RTF.
b
RTF=Ready-to-feed.
Table 4. Results of statistical analysis of the additional set
of data: average, RSD
r
, RSD
R
, and HorRat values
SMPR 2012.012
requirements
n
a
Avg.,
mg/100 g
≤5% ≤10%
RSD
r
, % RSD
R
, % HorRat
Infant formula RTF
(milk-based)
b
10
12.0 10.7 13.2
1.7
Adult nutritional
powder (low-fat)
10
17.6
1.5
6.5
0.9
a
n
represents the number of laboratories in the evaluation. No outliers
were removed.
b
RTF=Ready-to-feed.
226