the interlaboratory determination of npr and rnpr was also more reproducible than that of most essential amino acids ( cv up to 10.0 % ) , especially tryptophan ( cv up to 23.7 % ) , cystine ( cv up to 17.6 % ) , and methionine ( cv up to 16.1 % ) .
C0002525
essential amino
C0025646
methionine