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In this study, cyclic voltammetry and electrochemical ımpedance spectroscopy have been used to investigate the electrochemical behaviour of quercetin (3,3′,4′,5,7-pentahydroxyflavone) on the procaine and aminophenyl modified electrode. The modification of procaine and aminophenyl binded electrode surface with quercetin was performed in +0,3/+2,8 V (for procaine) and +0,4/+1,5 V (for aminophenyl) potential range using 100 mV s-1scanning rate having 10 cycle. A solution of 0.1 M tetrabutylammonium tetrafluoroborate in acetonitrile was used as a non-aquous solvent. For the modification process a solution of 1 mM quercetin in 0.1 M tetrabutylammonium tetrafluoroborate was used. In order to obtain these two surface, a solution of 1 mM procaine and 1 mM nitrophenyl diazonium salt in 0.1 M tetrabutylammonium tetrafluoroborate was used. By using these solutions bare glassy carbon electrode surface was modified. Nitrophenyl was reduced to amine group in 0.1 M HCl medium on the nitrophenyl modified glassy carbon elelctrode surface. Procaine modified glassy carbon electrode surface was quite electroactive. Although nitrophenyl modified glassy carbon elelctrode surface was electroinactive, it was activated by reducing nitro group into amine group. For the characterization of the modified surface 1 mM ferrocene in 0.1 M tetrabutylammonium tetrafluoroborate for cyclic voltammetry and 1 mM ferricyanide/ferrocyanide (1:1) mixture in 0,1 M KCl for electrochemical impedance spectroscopy were used.

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In this study, electrochemical modification of a glassy carbon (GC) electrode with apigenin was carried out and the modified electrode was used for determination of copper(II) (Cu(II)) in soil samples. The GC was modified through the electrochemical polymerization of apigenin (PolyApi/GC) on the electrode surface in aqueous media. The electrode surface was modified with apigenin in phosphate buffer solution (PBS), pH 7, from 0 mV to +1400 mV potential ranges, using 100 mV s À1 sweep rate and 30 cycles by cyclic voltammetry (CV). The surface characterizations of this sensor electrode were performed by CV, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Britton-Robinson (BR) buffer solution at pH 5 was used for determination of Cu(II) by differential pulse voltammetry (DPV). The detection limit was obtained as lower as 1.0 Â 10 À11 M. By using this calibration curve, the amount of Cu(II) was determined as 7.34 Â 10 À7 M in soil samples. The results showed that pH, incubation time and interferences of some cations and anions were significant.