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Stakeholder Comments
2.
The NIST 1849a table line 81. Arginine is listed twice. Actually I would suggest removing the
NIST 1849a data from the SMPR altogether The reason for this is how confident are we that the
.
reference values for the NIST standards are accurate for all amino acids? There are two facets to
this question. The first is that traditional methods for determining amino acids (ie, 24 hr HCl
hydrolysis at 110oC for the bulk of the amino acids, performic acid oxidation/HCl hydrolysis for
cysteine and methionine and base hydrolysis for tryptophan) do not accurately determine all
amino acids. For example, serine and threonine can be underestimated by as much 10‐15% and
some of the branched chain amino acids are difficult to hydrolysis and can be underestimated by
up to 10%. If traditional methods have been used to determine the amino acid composition of
the NIST 1849a then some of the values may not be accurate. The second facet relates to the fact
that if the NIST 1849a has been prepared in a similar way to regular infant formulas/adult
nutritionals then it potentially contain amino acids that have been modifies during the processing
of the material and if present, it is quite possible that some of these modified derivatives
interfere with the accurate determination of some amino acids.
Stakeholder Comments
2.(cont)
Arginine is not listed twice, the upper one is Alanine. It is true that the labeled reference
values of each amino acid for the NIST 1849a may be not as accurate as it should be when using
more advanced, more scientifically sound methodology. Some may change, how much we don’t
really know, as more research/discovery is made. For most of the amino acids, there is really no
special reason to suspect that the data may inaccurate. If results for select amino acids change
based on updated methodology, we would hope that NIST might issue a revised certificate or an
addendum. We believe that, despite the potential gaps, NIST 1849a remains the best choice as a
relevant SRM.
