Ligand exchange amino acid analysis: Resolution of some amino sugars and cysteine derivatives

A new buffer system has been developed for the Hitachi Perkin-Elmer model KLA-3B ligand-exchange amino acid analyzer (protein-hydrolyzates analysis) which allowed for virtually complete resolution of glucosamine and either mannosamine or galactosamine from the basic amino acids tyrosine and phenylalanine. The same buffer resolved S-(β-aminoethyl)cysteine from histidine. Although the resolution of the amino sugars was not affected by small pH changes in the buffer, the retention time of histidine was markedly changed. Elevation of the pH by 0.06 units caused histidine to elute with S-(β-aminoethyl)cysteine, while a similar decrease in pH caused it to elute with ammonia. A modified procedure for sample preparation was also tested that allowed for the complete resolution of S-carboxymethylcysteine from aspartic acid.