Rapid and simultaneous analysis of protein and non-protein amino acids as N(O,S)-isobutoxycarbonyl methyl ester derivatives by capillary gas chromatography

A simple and rapid gas chromatographic method is described for the simultaneous determination of protein and non-protein amino acids present in aqueous samples. The amino acids were converted into their N(O,S)-isobutoxycarbonyl methyl ester derivatives and measured by gas chromatography equipped with a split inlet mode, an electronic pressure control system and a hydrogen flame ionization detector using a DB-17ht capillary column. Using this method, the 21 protein amino acids and the 33 non-protein amino acids were quantitatively and reproducibly resolved within 25 min. The calibration curves were linear in the range 0.2-20 mu g of each amino acid, with correlation coefficients being above 0.998, and the relative standard deviations in each point ranged from 0.2 to 9.2%. The detection limits of amino acids were 0.09-1.15 ng per injection.