On the electrooxidation mechanism of quercetin glucosides at glassy carbon electrode

The present paper reports electrochemical (cyclic voltammetry and a.c. impedance) and spectroscopy (UV–VIS and HPLC–MS) studies of the process of adsorption and electrooxidation of two quercetin glucosides, namely: quercetin 3-O-β-glucoside (Q 3-glc) and quercetin 4′-O-β-glucoside (Q 4′-glc) at a glassy carbon electrode, in 0.1 M sodium acetate–acetic acid buffer in 90% methanol solution. The resulted information provided new insights into the mechanism of electrooxidation for two structurally different glucoside derivatives of quercetin, onto the surface of glassy carbon electrode. In addition, associated charge-transfer resistance (derived for all individual oxidation and electrosorption steps) and capacitance parameters are discussed and compared to those recently presented for quercetin aglycone.