Electrochemical interfacial adsorption mechanism of polyphenolic molecules onto Hanging Mercury Drop Electrode surface (HMDE)

The electrochemical interfacial adsorption of a series of polyphenolic molecules (i.e. polyhydroxybenzoic acids) at the Hanging Mercury Drop Electrode (HMDE)–electrolyte interfaces were investigated using Square Wave-Adsorption Cathodic Stripping Voltammetry (SW-AdCSV) at pH 7.5. Polyhydroxybenzoic acids bearing one 4-hydroxybenzoic acid, two 3,4-dihydroxybenzoic acid (protocatechuic) or three 3,4,5-trihydroxybenzoic acid (gallic) OH-groups at positions C3, C4 and C5 on the benzene ring were studied. The complex interfacial electrochemical behaviour of these molecules has been deconvoluted to (i) adsorption evens and (ii) redox formations at the HMDE interface. The approach presented is based on the comparative analysis of the SW-AdCSV signals in conjunction with the molecular structure of the molecules. Accordingly, theoretical calculations, involving nonlinear-fit, resulted in the identification of the interfacial reaction mechanism of adsorbed gallic acid on the HMDE.