Determination of Ascorbic Acid in Citrus Sinensis and Ananas Comosus Using Poly (3, 4-Ethylenedioxythiophene) Modified Glassy Carbon Electrode

Abstract

This study describes the preparation and application of a poly (3, 4-Ethylenedioxythiophene) (PEDOT) modified glassy carbon electrode for ascorbic acid determination in fruit samples by square wave voltammetric method. The PEDOT modified electrode was prepared by electrochemical polymerizing of 3, 4-Ethylenedioxythiophene (EDOT) on a glassy carbon electrode in a non-aqueous medium (0.1 M Tetrabutylammoniumhexafluorophosphate and 0.1 M EDOT in acetonitrile). The best performance of the PEDOT modified electrode in 0.1 M phosphate buffer was obtained at pH 5.0. In addition to this other parameters like electrode thickness, square wave amplitude, and square wave frequency were optimized. Under these conditions, an oxidation potential of ascorbic acid was observed at 395.24 mV versus Ag/AgCl/ reference electrode. The square wave voltammetric study indicated that the PEDOT modified electrode showed a very good electrocatalytic activity by reducing the overpotential by 113.69 mV for ascorbic acid oxidation. The modified electrode also showed a linear response range between 50 and 90µM. The proposed method was checked by determining the recovery of ascorbic acid in two commercially available tablets and provided an excellent recovery (i.e. 99.43 and 93.80%). Finally the method was applied in Orange and Pineapple fruits and 68.11±0.012 and 45.46±0.023 mg ascorbic acid per 100 g of the sample was found in each fruits respectively.