Electrocatalytic oxidation of ascorbic acid by immobilized silver nanoparticles on self-assembled L-cysteine monolayer modified gold electrode

The electrocatalytic oxidation of ascorbic acid in phosphate buffer solution (pH 7.0) by immobilized silver nanoparticles (Ag@CTAB) on L-cysteine modified gold electrode is reported. The modified electrode has been characterized electrochemically using redox couple [Fe(CN)6] . The electrocatalytic activity of the prepared electrodes is studied using cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical measurements show that the modified electrode (Au/L-cysteine/AgNPs) is highly active towards ascorbic acid oxidation. The oxidation peak of ascorbic acid at the Au/L-cysteine/AgNPs electrode is highly stable upon repeated potential cycling. The oxidation current of ascorbic acid increases upon each increment (0.05−0.35 μM) in differential pulse voltammetry experiments. The oxidation current shows a linear relationship with the concentration of ascorbic acid with a correlation coefficient of 0.996. The detection limit of ascorbic acid was found to be 2×10 M. Common physiological interferents such as glucose, tartaric acid, citric acid and cysteine do not show any interference within the detection limit of ascorbic acid. The silver nanoparticles modified gold electrode has been used to determine the amount of ascorbic acid present in fruit and vegetable juices.