CAPILLARY GAS-CHROMATOGRAPHY OF PROTEIN AMINO-ACIDS AS N(O,S)-ISOBUTYLOXYCARBONYL TERT-BUTYLDIMETHYLSILYL DERIVATIVES IN AQUEOUS SAMPLES

A method for the quantitative determination of the nineteen protein amino acids by gas chromatography is described. The amino acids were allowed to react with isobutyl chloroformate in a basic aqueous medium and the resulting N(O,S)-isobutyloxycarbonyl (isoBOC) amino acids were extracted into an organic solvent after acidification. The isolated N(O,S)-isoBOC amino acids were then converted to stable tert.-butyldimethylsilyl (TBDMS) derivatives, which were analyzed by gas chromatography and gas chromatography-mass spectrometry. The characteristic [M - 57], [M - 113], [M - 159], [M - 174], etc. ions in the mass spectra of N(O,S)-isoBOC TBDMS derivatives enabled rapid confirmation of the amino acids. Temperature-programmed retention index (1) sets measured on DB-5 and DB-17 capillary columns were characteristic of each amino acid thus being useful for the quick identification by computer I matching. The overall extraction and derivatization yields of the amino acids studied were linear in the range of 20-80-mu-g.