GB/T 18246-2019 Active

This standard specifies the methods for determining total amino acids (peptide bond-bound and free) and free amino acids (natural and added) in feed, including conventional acid hydrolysis, oxidative acid hydrolysis, alkaline hydrolysis, and acid extraction. Conventional acid hydrolysis is suitable for determining the content of amino acids (aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine, and arginine) except sulfur-containing amino acids (cysteine, cystine, and methionine) in feed raw materials, compound feed, concentrated feed, supplementary feed, and premix feed. Oxidative acid hydrolysis is suitable for determining the content of sulfur-containing amino acids (cysteine, cystine, and methionine) in feed raw materials, compound feed, concentrated feed, and supplementary feed. When sodium metabisulfite is used as the oxidation terminator, other proteolytic amino acids except tyrosine and tryptophan can be determined; when hydrobromic acid is used as the terminator, other proteolytic amino acids except tyrosine, phenylalanine, histidine, and tryptophan can be determined. Alkaline hydrolysis is suitable for determining the content of tryptophan in feed raw materials, compound feed, concentrated feed, and supplementary feed. Acid extraction is suitable for determining the content of free amino acids in compound feed, concentrated feed, supplementary feed, and premix feed. The quantitative limits of each amino acid are shown in Table A.1 in Appendix A.