Cyclic voltammetry, differential pulse voltammetry and double potential step chronoamperometry were used to investigate the electrochemical behavior of ascorbic acid (AA) at a chemically modified electrode prepared by incorporating 2,7-bis (ferrocenyl ethynyl) fluoren-9-one (2, 7-BFEFO) into carbon paste matrix. Under the optimized conditions (pH 7.00), the modified electrode showed high electrocatalytic activity toward AA oxidation; the overpotential for the oxidation of AA was decreased by more than 200 mV and the corresponding peak current increased significantly. In fact, the Fc/ Fc+ redox couple acts as a suitable mediator for indirect oxidation of AA. The diffusion coefficient (D =8.65×10-6 cm2 s-1), and the kinetic parameters such as electron transfer coefficient, (α = 0.47) and the catalytic reaction rate constant, (k=8.55×103 M-1 s-1 ) were also determined using electrochemical approaches. The voltammetric response of the modified electrode was linear against the concentration of AA in the ranges of 5×10-5 M-2.65×10-3 M and 9×10-6 M-3.5×10-3 M with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, respectively. The detection limits (2σ) were determined as 1.8×10-5 M and 4.2×10-6 M by CV and DPV methods, respectively. This method was also used for determination of AA in some pharmaceutical preparations.
