Determination of glutathione and related aminothiols by gas chromatography with flame photometric detection

A selective and sensitive method for the determination of glutathione (GSH) and related aminothiols such as cysteine (Cys), cysteinylglycine (CysGly) and gamma-glutamylcysteine (gamma-GluCys) by gas chromatography (GC) has been developed. GSH and related aminothiols were converted into their N,S-isopropoxycarbonyl methyl ester derivatives and measured by GC with flame photometric detection using a short capillary column (5 m x 0.53 mm i.d.) of cross-linked DB-1. The calibration curves were linear in the range 1-25 nmol for GSH and in the range 0.2-5 nmol for other aminothiols, and the detection limits of GSH, Cys, CysGly and gamma-GluCys were approximately 5, 0.2, 0.3 and 0.5 pmol per injection respectively. This method was successfully applied to blood samples without prior clean-up, and GSH and related aminothiols in these samples could be analysed without any influence from coexisting substances. Overall recoveries of GSH and other aminothiols added to blood samples were 88-107%. The analytical results of free and total blood GSH and related aminothiols in normal subjects are presented.