Voltammetric detection of glutathione: an adsorptive stripping voltammetry approach

A simple, sensitive, and rapid detection of glutathione by cyclic voltammetry using a bare glassy carbon electrode is reported in which glutathione forms a 1 : 1 complex compound with copper(II) ions. This complex compound is adsorbed onto the electrode surface and undergoes electrochemical oxidation at a characteristic oxidation potential of ca. -0.20 V vs. the standard mercury/mercurous sulphate reference electrode, which is used to detect the glutathione concentration. The linear dynamic range is obtained for a glutathione concentration from 1 mu M to 12.5 mu M, and the sensitivity is found to be 0.1 +/- 0.002 mu A mu M-1. A low limit of detection (n = 3) of 0.14 mu M and a precision of 1.8% are achieved using a simple, unmodified electrode. The robustness of the present methodology is demonstrated by the successful quantitative analysis of glutathione in the presence of cysteine.