Electrochemical determination of reduced glutathione (GSH) by applying the powder microelectrode technique

The apparent reversibility of the electrochemical oxidation of GSH can be significantly improved by using the powder microelectrode (PME) technique. The over-potential of GSH oxidation at an acetylene black-packed powder microelectrode (AB-PME) is about 0.5 V more negative than that obtained with the Pt and glass carbon electrodes. From the value of limiting current on the steady-state polarization curve obtained with the AB-PME, the number of electron involved in the electrochemical oxidation of GSH was calculated to be 1. After stabilizing AB-PME by prolonging incubation and cycling in the solution containing GSH, the exhaustive electrolysis of GSH entrapped within the microcavity of the PME can be achieved during CV measurements. As the result, the peak currents obtained with AB-PME were found to be proportional to the concentration of GSH in the solution. The detection sensitivity is 0.57 mA/mM cm2, and the linear range of calibration curve is 0.1–2.8 mM. Besides, the exhaustive electrolysis of coexisting ascorbic acid (AA) and uric acid (UA) can also be achieved in CV measurements, resulting in the complete separations of the corresponding anodic current peaks from that caused by GSH. Consequently, the interferences due to AA and UA can be completely eliminated. The concentration of GSH in human erythrocyte was successfully determined with the AB-PME by applying the method of ‘internal standard addition’ technique.