A Differential Pulse Voltammetric Sensor for Determination of Glutathione in Real Samples Using a Trichloro(terpyridine)ruthenium(III)/Multiwall Carbon Nanotubes Modified Paste Electrode

A trichloro(terpyridine)ruthenium(III) modified-multiwall carbon nanotubes paste electrode (TChPRuMWCNTPE) was fabricated and used as an electrocatalyst for the oxidation of glutathione (GSH). The effects of variables, such as pH and modifier percentage, were optimized using cyclic voltammetric method. The modified electrode shows a very efficient electrocatalytic activity for the anodic oxidation of GSH in the presence of 0.1 mol L^-1 phosphate buffer solution (pH = 8.0). The oxidation peak potential of the GSH at a surface of TChPRu-MWCNTPE is appeared at 270 mV that is ~330 mV lower than the oxidation peak potential at the surface of a traditional carbon paste electrode in the same condition. The kinetic parameters, such as electron transfer coefficient, rate constant for the chemical reaction between GSH and the redox site in TChPRu-MWCNTPE, and apparent diffusion coefficient (D), was determined in an aqueous buffered solution. The electrocatalytic currents increase linearly with the GSH concentration over the concentration range of 0.6-56.8 μ mol L^-1. The detection limit for GSH was found to be 0.3 μ mol L^-1. In addition, the theoretical calculations were performed to determine the Gibbs free energy changes of the conversion of trichloro(terpyridine)ruthenium(II)(TChPRu´) to TChPRu in the acidic and basic media, separately. Finally, this method was examined as a simple and precise electrochemical sensor for determination of GSH in the real samples such as hemolyzed erythrocyte and urine.