Biosensors & Bioelectronics

Quantifying Reduced Glutathione by Square-wave Voltammetry

Abstract

Marcos Vergilio Corrêa-da-Silva, Acácio Antonio Pigoso, Beatriz Felicio Ribeiro, Laís Oliveira Barbosa, Claudio Aparecido Rosado Miloch and Armindo Antonio Alves

This study examines the use of square wave voltammetry (SWV) to quantify reduced glutathione (GSH) dissolved in phosphate buffer (pH 7.5) using a static mercury drop electrode (working), Ag/AgCl electrode (standard) and a platinum wire (auxiliary). The applied voltage ranged from -0.7 to -0.2 V. Increasing concentrations of GSH (13-188 μmol/L) correlated with the voltammogram peak area (R²=0.99) and with the current at peak potential (Ip) (R=0.99). The reaction of GSH with diamide was monitored for validation of the method. Addition of increasing concentrations of diamide (13.3-50.8 μmol/L) to a fixed concentration of GSH (120 μmol/L) decreased the Ip, and the results obtained presented a relative deviation (RD) ≤ 14.5% (compared with expected concentrations by stoichiometry) for GSH concentrations above 33.8 μmol/L, whereas the spectrophotometric method (Elman’s reagent) presented RD ≤ 25.6%. These data indicate that SWV method is more accurate and presented equal precision (SD<8%) as compared to the commonly used spectrophotometric method. This method seems suitable for measuring GSH concentrations at room temperature and pH 7.5 (near biological conditions). Other advantages of this method that make it highly desirable for rapid diagnostic purposes include low cost, simplicity, sensitivity, rapid response and no prior sample preparation.