Novel sensor based on carbon paste/Nafion® modified with gold nanoparticles for the determination of glutathione

Several problems for the direct electrochemical oxidation of reduced glutathione (GSH) challenge the usage of electroanalytical techniques for its determination. In this work, the electrochemical oxidation of GSH catalyzed by gold nanoparticles electrodeposited on Nafion modified carbon paste electrode in 0.04 mol L−1 universal buffer solution (pH 7.4) is proved successful. The effect of various experimental parameters including pH, scan rate and stability on the voltammetric response of GSH was investigated. At the optimum conditions, the concentration of GSH was determined using differential pulse voltammetry (DPV) in two concentration ranges: 0.1 × 10−7 to 1.6 × 10−5 mol L−1 and 2.0 × 10−5 to 2.0 × 10−4 mol L−1 with correlation coefficients 0.9988, 0.9949 and the limit of detections (LOD) are 3.9 × 10−9 mol L−1 and 8.2 × 10−8 mol L−1, respectively, which confirmed the sensitivity of the electrode. The high sensitivity, wide linear range, good stability and reproducibility, and the minimal surface fouling make this modified electrode useful for the determination of spiked GSH in urine samples and in tablet with excellent recovery results obtained.