Preparation and electrochemical study of fisetin modified glassy carbon electrode. Application to the determination of NADH and ascorbic acid

A new modified electrode, FMGCE, was prepared by electrodeposition of fisetin (F) at the surface of a preactivated glassy carbon electrode. Cyclic voltammetry was used to investigate the electrochemical properties of this electrode. The charge transfer rate constant, k(s), and transfer coefficient, a,, for electron transfer between electrode substrate and surface deposited F were calculated as 16.34 s(-1) and 0.54, respectively. The electrode ability towards the electrocatalytic oxidation of dihydronicotinamide adenine dinucleotide (NADH) and ascorbic acid (AA) was also studied using cyclic voltammetry and chronoamperometry as diagnostic techniques. The catalytic currents of NADH and AA were used for determination of heterogeneous rate constant, k(h), of these substrates oxidation at the surface of modified electrode. The diffusion coefficients of both substrates were also estimated using chronoamperometric results. Finally, FMGCE was used as voltammetric and amperometric sensors for determination of NADH and AA in quiet and moving solutions respectively. The calculated limit of detection of NADH and AA by voltammetry were 0.06 and 0.05 mM, respectively. While, these values decrease to 2.4 and 1.8 mu M, respectively for an amperometric procedure. The latter method was used successfully for quantification of AA in some real samples.