Electrochemical Determination of Ascorbic Acid Using Modified Glassy Carbon Electrode by Multiwall Carbon Nanotube-Nafion in Chloroacetic Acid Media

In this study, ascorbic acid was simply determined at lower potential compared to bare glassy carbon by replacement phosphate buffer solution with chloroacetate buffer solution at surface of modified glassy carbon electrode. A film of Nafion with multi-walled carbon nanotubes (MWCNT) was prepared by rapidly casting solution onto the surface of a glassy carbon electrode and drying under room temperature. For MWCNT-Nafion film was not observed any peaks in the used potential range in phosphate buffer solution. However, by replacing phosphate buffer solution with chloroacetate buffer solution, due to interaction between nafion film and component of chloroacetate buffer solution in a positive scan, an oxidation peak was obtained at about 0.442 V and at a reversal scan a reduction peak was observed at about 0.282 V. Scan rate, pH and interference effects for the determination of ascorbic acid were studied. It was found that glassy carbon electrode/MWCNT-Nafion in chloroacetate buffer solution pH = 2, increase significantly the cyclic voltammogram peak currents as well as a decreasing the oxidation overpotentials of ascorbic acid compared to bare glassy carbon. A linear range between 5.0 x 10(-5) mol/L and 2.32 x 10(-2) mol/L and a detection limit (3 sigma) 1.2 x 10(-5) mol/L was obtained for modified electrode. Finally, the novel modified electrode was successfully applied to the determination of ascorbic acid in pharmaceuticals and foods in acetate medium.