Electrochemical Behaviour of Antioxidants: Part 2. Electrochemical Oxidation Mechanism of Quercetin at Glassy Carbon Electrode Modified with Multi-Wall Carbon Nanotubes; a Voltammetric and Chronocoulometric Study

The electrochemical oxidation mechanism of quercetin at glassy carbon electrode modified with multi-wall carbon nanotubes in aqueous 0.2 M phosphate solutions with different pH values was studied using cyclic voltammetry and the double potential step chronocoulometric method. It was found that the oxidation proceeds in sequential steps, related to the five hydroxyl groups in the three aromatic rings. The oxidation mechanism was deduced by matching the experimental chronocoulometric charge ratio versus the logarithm of duration time plots to the theoretical working curves for different electrode mechanisms. It was concluded that the electrode reaction follows an ECEC, first-order mechanism. The proposed mechanism was confirmed by digital simulation using DigSim 3 software. The simulation was performed by comparing the simulated responses with the experimental ones. The homogeneous and heterogeneous kinetic parameters of the electrode reaction are estimated from the simulated data. Furthermore, it was found that, quercetin is strongly adsorbed on the electrode surface.