A new method for the determination of optical purity of synthetic peptides

A novel and very accurate method was established for the determination of the optical purity of a peptide by use of the following procedure: (1) hydrolysis of the peptide in deuterium chloride, (2) gas chromatographic separation of each amino acid enantiomer on a chiral phase, and (3) determination of the D/L ratio by mass fragmentography. In this manner, one can estimate the true chiral purity of each amino acid residue with an accuracy of ∼0.2%. The recemization effected during hydrolysis could be eliminated in principle, since the artificially formed DL‐amino acids are necessarily labeled at the α‐position with deuterium and can thus be distinguished mass spectrometrically from the D‐ and L‐isomer originally present in the peptide. The versatility of the method was proven by analysis of model peptides, as well as by a racemization test in fragment condensation.