Electrochemical Behavior of Glutathione (Oxidized form) on the Mercury Electrode ?

Abstract

The electrochemical behavior of glutathione (oxidized form, GSSG) on the mercury electrode has been studied in buffer solution of pH 2.5 to 10. In acetate buffer (pH 5.0), GSSG yielded 1 to 3 reduction peaks on cyclic voltammograms with increasing the concentration GSSG. GSSG in the concentration of 3.5× 10-4 moll/ (Eτ = 0 V, V= 3 V/s) gave three reduction peaks at hanging mercury drop electrode (HMDE). The potential of the first peak was O4.2 V, the second peak being O5.1 V and the third peak being 0.7 2 V vs. SCE. The first and the third peaks had the natures of adsorption and diffusion peak, respectively. Since the second psak had the nature of both adsorption and diffusion peak, it was supposed to be the reduction peak of the multilayer. The maximum catho dic peak currents of the first peak of GSSG and the adsorption peak of glutathione (reduced form, GSH) were different from each other. This suggested that the adsorption species of GSSG and GSH were different. Traces of mercury compound were detected after the controlled potential electrolysis at 0 V vs. SCE. This result indicated the change of a little GSSG to (GS) 2Hg. Coulometric reduction of GSSG at mercury pool of 1.0 V vs. SCE gave an n=1.9 9. Therefore the reduction schemes of the first and the thir d peaks were deduced as follows: The first peak; GSSGads+ 2 H + + 2–: e→ + 2 G SHsoin Hg (GS )2Hgads + 2H++2e⇔ 2 GSHBoin + Hg The third peak; GSSGsoin + 2 H + + 2 e→2GSHsoln When the sweep rate was low ered to 10 m V/s, the peak current-concentration curve for GSSG was linear from 1× 10-5 mol/l to 5× 10-4 mol/l. The presence of GSH up to 5×10-4mol/l had no effect on 1× 10-4 m ol/l GSSG for simultaneous quantitative analysis for GS SG and GSH.