Glutathione and cysteine measurement in biological samples by HPLC with a glassy carbon working detector

An HPLC method using a glassy carbon working detector for measuring cysteine and reduced glutathione (GSH) in biological samples was developed. Oxidized glutathione (GSSG) was also measured after reduction with glutathione reductase. This study was conducted in human plasma. Cysteine and GSH standard curves were linear in the physiological range, presenting detection limits of 22.0 pmol and 6.0 pmol respectively. Plasmatic results found were 43.92 +/- 4.15, 4.50 +/- 0.65, and 0.19 +/- 0.12 mM (means +/- SE), for cysteine, GSH and GSSG, respectively. Peak specificity for cysteine and reduced glutathione was certified by their disappearance after treatment with N-ethylmaleimide.