ISO 17180:2013 specifies a method for the quantitative determination of free (non-protein-bound) lysine, methionine, and threonine in commercial products and premixtures containing more than about 10 % mass fraction of the respective amino acid. It does not distinguish between d- and l-forms.
NOTE For the purposes of this International Standard, the term “amino acids” used in Clause 2 onwards refers to lysine, methionine, and threonine.
