A micromethod for the analysis of free amino acids by gas chromatography and its application to biological systems.

A gas chromatographic procedure was developed for determination of minute amounts of free amino acids in natural waters and laboratory models simulating biological systems. Sample pretreatment included removal of interfering organic substances by chloroform extraction and isolation of amino acids by cation exchange. Amino acids were converted to their N-heptafluorobutyryl isobutyl ester derivatives in glass capillary tubes, permitting considerable concentration of the sample prior to gc injection. The derivatives of 19 amino acids were successfully separated on either a glass column packed with a mixture of OV-101 and OV-17 on Chromosorb W, a glass capillary column coated with OV-101, or a support-coated capillary column supported with SE-30. One to five nanograms of individual amino acids were detected using flame ionization detector. The detection limit was reduced more than 100-fold using the electron capture detector and more than 1000-fold by mass fragmentography. The procedure allowed determination of less than 1 ppb of individual amino acids in lake and river water samples and was used to estimate the exeretion of free amino acids from microbial populations.