DETERMINATION OF TOTAL PLASMA HOMOCYSTEINE AND RELATED AMINOTHIOLS BYGAS-CHROMATOGRAPHY WITH FLAME PHOTOMETRIC DETECTION

A selective and sensitive method for the determination of total homocy steine (Hcy) and related aminothiols, such as cysteine (Cys) and cyste inylglycine (CysGly), in plasma samples by gas chromatography (GC) has been developed. After reduction of the sample with sodium borohydride , the liberated Hcy and other aminothiols were converted to their N,S- diisopropoxycarbonyl methyl ester derivatives and measured by GC with flame photometric detection using a DB-17 capillary column. The calibr ation curves were linear over the range 0.5-10 nmol for Hcy and CysGly , and over the range 5-100 nmol for Cys, and the correlation coefficie nts were above 0.996. Using this method, total plasma Hcy, Cys and Cys Gly could be directly analysed without prior clean-up of the sample an d without any interference from coexisting substances. Overall recover ies of Hcy and other aminothiols added to plasma samples were 95-106%. Analytical results for the determination of total plasma Hcy, Cys and CysGly from normal subjects are presented.