296 / 620
milk protein based powder was slightly above the SMPR guideline of ≤ 11% for
repeatability (RSD
r
), while the Indian vitamin D
2
infant formula powder, adult nutritional
low fat powder and the adult nutritional high fat RTF were slightly above the SMPR
guideline of ≤ 15% for reproducibility (RSD
R
).
Historically, adult nutritional powders that are high in fat and protein have been difficult
to analyze for fat soluble vitamins. Laboratories often experience more variability with
this type of a matrix when compared to other types of adult nutritional matrices [3] [4]
[5]. The single laboratory validation (SLV) conducted by Covance Laboratories
demonstrated a relative standard deviation (RSD
r
) of 11.0% for the adult nutritional milk
protein based powder and was amongst one of the higher RSD
r
values obtained during
this study [6]. Despite the RSD
r
value of 13.5%, the HorRat value is 0.36 or this matrix,
which is well below the maximum limit of 2.0 and the RSD
R
meets the SMPR guideline.
Given the low level of analyte in this matrix, the study directors consider the high RSD
r
value to be acceptable.
For the Indian vitamin D
2
infant formula powder, the adult nutritional low fat powder and
the adult nutritional RTF high fat samples, the RSD
R
values of 16.2, 16.0, and 15.8%
only slightly exceed the maximum limit, while the RSD
r
values are acceptable at 3.52,
3.08, and 4.21%. These samples also demonstrated acceptable HorRat values of 0.52,
0.43, and 0.51 and therefore, the Study Directors consider the level of variability between
laboratories (RSD
R
) to be acceptable.
The overall results demonstrate that the method is fit-for-purpose to determine vitamin
D
2
and D
3
in infant formulas and adult/pediatric nutritional formulas and the Study
Directors recommend that it be adopted Official Final Action.
Laboratory Comments
The comments made by the participating laboratories are presented below. All the
comments were reviewed and did not indicate any issues or concerns with the data. The
use of reagent alcohol to address emulsions will be added to the method as suggested by
Laboratory M. It was also suggested by a member of the ERP to include a
spectrophotometric reading of the standard material to determine the purity. This
procedure will be included and outlined in the method.
Laboratory B noted that the %RSD for both the vitamin D
2
and D
3
standards were above
the targeted 3% for the instrument check.
Laboratory C used an Accucore C18 column with an Accucore C18 guard column for
analysis.
Laboratory D found the method relatively easy to perform in their laboratory and allows
for the analysis of an appropriate number of samples per day. Their recommendation
would be to clarify the different transitions in the method.
Laboratory G noted that a sample size of 11-12 g was used for the RTF and reconstituted
powders. They used a single tube for saponification and extraction and the sample was
pulled using a vacuum prior to dry down and reconstitution. This laboratory also
collected two days of data but only day one was included in the study results.
2011.11 VITAMIN D MLT-Sept 2015
FOR ERP USE ONLY
DO NOT DISTRIBUTE