Voltammetric method for determination of glutathione on a gold-carbon-containing electrode

Abstract

Glutathione (GSH) is one of the most important thiol-containing antioxidants involved into various biochemical processes in the human body. Glutathione determination in biological fluids (saliva, urine, serum) and pharmaceutical preparations is rather important for clinical practice. Various analytical methods — spectrophotometry, fluorimetry, high-performance liquid chromatography, NMR spectroscopy, capillary electrophoresis and electrochemical methods — are widely used for this purpose. Electrochemical methods are characterized by easy implementation, low cost and possibility of miniaturization. The electrochemical behavior of reduced (GSH) and oxidized (GSSG) glutathione on a gold-carbon-containing electrode (AuCE) was studied using cathodic voltammetry with different methods of removing oxygen from an electrochemical cell: nitrogen sparging and addition of sodium sulfite (4 mol/dm3). It has been shown that traces of H2O2 that remain in the near-electrode layer on the AuCE even after oxygen removal influence the electrochemical properties of GSH at a cathode sweep of the potential from 0 to –1.8 V: GSH is oxidized by H2O2 to GSSG, the most important product of this reaction is O2. An indirect determination of GSH by the current of oxygen reduction in the Na2SO3 medium in the concentration range from 0.5 × 10–8 to 4.2 × 10–8 mol/dm3 with a detection limit of 2.5 × 10–9 mol/dm3 is proposed. The developed voltammetric method is approved for the determination of GSH in certain pharmaceutical preparations.