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

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Abstract
A selective and sensitive method for the determination of glutathione (GSH) and related aminothiols such as cysteine (Cys), cysteinylglycine (CysGly) and γ‐glutamylcysteine (γ‐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 × 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 γ‐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.