Voltammetric sensor for glutathione determination based on ferrocene-modified carbon paste electrode

The electrocatalytic oxidation of glutathione (GSH) has been studied at the surface of ferrocene-modified carbon paste electrode (FMCPE). Cyclic voltammetry (CV), double potential step chronoamperometry, and differential pulse voltammetry (DPV) techniques were used to investigate the suitability of incorporation of ferrocene into FMCPE as a mediator for the electrocatalytic oxidation of GSH in buffered aqueous solution. Results showed that pH 7.00 is the most suitable for this purpose. In the optimum condition (pH 7.00), the electrocatalytic ability of about 480 mV can be found and the heterogeneous rate constant of catalytic reaction was calculated as k(h)' = 83 x 10(-1) cm s(-1). Also, the diffusion coefficient of glutathione, D, was found to be 3.61 x 10(-5) cm(2) s(-1). The electrocatalytic oxidation peak current of glutathione at the surface of this modified electrode was linearly dependent on the GSH concentration and the linear analytical curves were obtained in the ranges of 3.2 x 10(-5) M-1.6 x 10(-3) M and 2.2 x 10(-6) M-3.5 x 10(-3) M with cyclic voltammetry and differential pulse voltammetry methods, respectively. The detection limits (3 sigma) were determined as 1.8 x 10(-5) M and 2.1 x 10(-6) M using CV and DPV, respectively. Finally, the electrocatalytic oxidation of GSH at the surface of this modified electrode can be employed as a new method for the voltammetric determination of glutathione in real samples such as human plasma.