Plasma amino acid analysis by isotope ratio gas chromatography mass spectrometry computer techniques.

A routine analysis for micro samples of plasma amino acids by a gas chromatography mass spectrometry computer system has been developed. Isotope ratio determination was used as the quantitating technique via multiple internal standards. The speed of the analysis is increased by omitting the ion exchange purification step and its flexibility is maximized by using repetitive scanning rather than selective ion monitoring. This procedure yields excellent precision and accuracy, as demonstrated by the analysis of a known amino acid mixture and of neonatal plasma.