Electrochemical behaviour of antioxidants: Part 2. Electrochemical oxidation mechanism of quercetin at glassy carbon electrode modified with multi-wall carbon nanotubes

Electrochemical oxidation mechanism of quercetin was investigated at glassy carbon electrode modified with multi-wall carbon nanotubes in aqueous 0.2 M phosphate solutions with different pHs. The investigation was carried out using cyclic voltammetry, double potential step chronoamperometric and chronocoulometric techniques. It was found that the oxidation mechanism proceeds in sequential steps, related with the five-hydroxyl groups in the three aromatic rings. The mechanism was proposed to be an ECEC, first-order kinetics. The proposed mechanism was confirmed on comparing the digital simulated cyclic voltammetric responses with the experimental ones. The electrode homogeneous and heterogeneous kinetic parameters of electrode reaction are estimated from the simulated data. Moreover, quercetin molecules adsorb on the electrode surface.