Voltammetric measurement of trace amount of glutathione using multiwall carbon nanotubes as a sensor and chlorpromazine as a mediator

In this work, we propose chlorpromazine as a new mediator for the rapid, sensitive, and highly selective voltammetric determination of glutathione (GSH) using multiwall carbon nanotubes paste electrode (MWCNTPE). The experimental results showed that the carbon nanotubes paste electrode has a highly electrocatalytic activity for the oxidation of GSH in the presence of chlorpromazine as a mediator. Cyclic voltammetry, double potential step chronoamperometry, and differential pulse voltammetry (DPV) are used to investigate the suitability of chlorpromazine at the surface of MWCNTPE as a mediator for the electrocatalytic oxidation of GSH in aqueous solutions. It is shown that chlorpromazine can catalyze the oxidation of GSH in an aqueous buffer solution to produce a sharp oxidation peak current at about +0.70 versus Ag/AgCl as a reference electrode. Kinetic parameters such as electron transfer coefficient and catalytic reaction rate constant, k/h, are also determined. Using DPV and under the optimum conditions at pH 4.0, the electrocatalytic oxidation peak current of GSH shows a linear dependence on GSH concentration in the GSH concentration range of 0.3 to 18.3 µM. The detection limit (3σ) is determined to be 0.16 µM. The relative standard deviation for 1.5 and 5.0 µM GSH are found to be 3.7% and 2.5%, respectively. The proposed method may, thus, also be used as a novel, selective, simple, and precise method for the voltammetric determination of GSH in such real samples as hemolyzed erythrocyte.