Square-Wave and Cyclic Voltammetry of Native Proanthocyanidins Extracted from Grapevine (Vitis vinifera) on the Glassy Carbon Electrode

Abstract

Condensed tannins are short polymers of flavan-3-ols found in grapes (also known as proanthocyanidins). An investigation on the electrochemical oxidation of grapevine proanthocyanidins (PAs) on glassy carbon electrodes under various conditions was conducted for the first time. To study how the proanthocyanidins were oxidized, square-wave and cyclic voltammetry were used. There is a predominant oxidation peak associated with the extract of proanthocyanidins, and this can be attributed to the oxidation of catechol 3′,4′-dihydroxyl groups, which can form their oxidation peak. There are two electrons and two protons involved in the oxidation of the catechol group, which must be kept in mind when considering the oxidation of the catechol group. On the glassy carbon electrode (GCE), the PAs extracted from grapevine are oxidized by an adsorption-dependent mechanism as they interact with the GCE surface. As a result, it was found that the anodic peak current varied linearly with PAs’ concentrations in the range of 4 to 50 ppm, with a detection limit of 3.07 ppm (S/N = 3). There was a development in the surface concentration of the oxidation products at the GC electrode; as the scans progressed, the surface concentration of oxidation products at the electrode remained at 4.83 × 10−11 mol cm−2, indicating that they were immobilized on the GCE as oxidation products adsorbed on the electrode.