334 / 435
C
ampos
-G
iménez
et al
.:
J
ournal of
AOAC I
nternational
V
ol
.
96, N
o
. 5, 2013
1067
products or as “reconstituted powder” for powder samples, as
follows:
[ [ 9P[6
[ [ 9 [ 9 ,$ &
where A = response (height or area) of the ascorbic acid peak
obtained for the sample solution, m = weight of the test portion
in g (2.0 g), V
1
= volume of the test solution (volume used to
dissolve the test portion) in mL (10 mL), V
2
= volume used
in the sample dilution (1.0 mL), and V
3
= volume of the final
sample dilution (10 mL).
Note
: If results expressed in powder sample are needed, use
the reconstitution rate to calculate (c
×
225/25).
Results
The results from the single-laboratory validation in a selected
set of matrixes presented here show the method is suitable for the
determination of vitamin C in infant formula and adult/pediatric
nutritional formula. Accuracy rates were 90–100%. Duplicate
analyses on 7 days showed RSD of repeatability (RSD
r
) ranged
from 1.4 to 2.5%, and intermediate precision RSD (RSD
iR
)
from 1.3 to 7.5% (Table 1). The linearity was demonstrated by
R
2
> 0.999 and calibration error lower than 5% in the range
of 0.5–10 µg/mL, which corresponds to a quantification range
of 2.5–50 mg/100 g (expressed for reconstituted product).
Standard Reference Material SRM 1849a (infant/adult
nutritional formula) was analyzed in duplicate over 7 days; the
overall mean was found to be 8.39 mg/100 g, with an SD of the
mean of duplicates of 0.10 mg/100 g, which was statistically
not different from the reference value (7.84 ± 0.65 mg/100 g).
The average recovery from spiked samples (duplicate analysis,
3 days) at 50 and 100% of target levels ranged from 94 to 101%
with an RSD of 4.7–14.5%, and from 94 to 100% with an RSD
of 3.9–5.8%, respectively (Table 2). These results validate the
modified method for determining vitamin C in infant formula
and adult/pediatric nutritional formula. Figures 1 and 2 show
example chromatograms.
References
(1) Türkez, H., & Aydin, E. (2012)
Toxicol. Ind. Health
28
,
684–654
(2) Fontannaz, P., Kilinc, T., & Heudi, O. (2006)
Food Chem.
94
,
626–631.
http://dx.doi.org/10.1016/j.foodchem.2005.02.012(3) AOAC SMPR 2012.012 (2013)
J. AOAC Int.
96
, 491. http://
dx.doi.org/10.5740/jaoac.int.SMPR2012.012$VFRUELF
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Figure 1. Example chromatograms of infant formula
powders/certified reference material.
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Figure 2. Example chromatograms of nutritional
products.
AOAC OMB Meeting Book
309