Abstract
Electrochemical oxidation of quercetin, as an important biological molecule, has been studied in non-aqueous media using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. To investigate the electrochemical properties of quercetin, an important flavonoid derivative, on a different surface, a new glassy carbon electrode has been developed using dithiooxamide as modifier in non-aqueous media. The surface modification of glassy carbon electrode has been performed within the 0.0 mV and +800 mV potential range with 20 cycles using 1 mM dithioxamide solution in acetonitrile. However, the modification of quercetin to both bare glassy carbon and dithiooxamide modified glassy carbon electrode surface was carried out in a wide +300 mV and +2,800 mV potential range with 10 cycles. Following the modification process, cyclic voltammetry has been used for the surface characterization in aqueous and non-aqueous media whereas electrochemical impedance spectroscopy has been used in aqueous media. Scanning electron microscopy has also been used to support the surface analysis. The obtained data from the characterization and modification studies of dithioxamide modified and quercetin grafted glassy carbon electrode showed that the developed electrode can be used for the quantitative determination of quercetin and antioxidant capacity determination as a chemical sensor electrode.
Highlights
Electrochemical and spectroelectrochemical measurements leading to the determination of kinetic parameters for antioxidants, are very relevant, for evaluating the antioxidative abilities of flavonoids [1], and for understanding their reaction mechanisms
After the modification of the glassy carbon (GC) electrode, the surface of obtained dithiooxamide modified GC (DTO/GC) electrode was washed in order to remove all impurities from the electrode surface and it was used for other investigations described in this study
The electrochemical and spectrochemical properties of QR on DTO modified GC (DTO/GC) electrode surface was studied in non-aqueous media
Summary
Electrochemical and spectroelectrochemical measurements leading to the determination of kinetic parameters for antioxidants (e.g., redox potential, number of electrons transferred, electrode reaction rate constant, etc.), are very relevant, for evaluating the antioxidative abilities of flavonoids [1], and for understanding their reaction mechanisms. The half-wave potential (E1/2) is a useful parameter for supplying information on the scavenging activity of the flavonoids This has been rationalized on the basis that both electrochemical oxidation and hydrogen-donating free radical scavenging involve the breaking of the same phenolic bond between oxygen and hydrogen, producing the phenoxy radical and hydrogen, in an electron and proton transfer reaction. Liu and Guo [21] studied the interaction of flavonoid, quercetin with organized molecular assemblies of nonionic surfactant On account of these properties it is widely used as beneficial food supplement that is recommended for prevention and suppression of many diseases. The electrochemical mechanism of oxidation of quercetin dihydrate was investigated, for a wide range of non-aqueous solution conditions onto the dithiooxamide modified GC electrode surface, using CV, EIS and SEM techniques. Information on the mechanism of quercetin oxidation obtained from results at studies may play a crucial role in understanding its antioxidant activity
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