Amperometric determination of sulfide based on its electrocatalytic oxidation at a pencil graphite electrode modified with quercetin

This study describes a new approach for the investigation of electrocatalytic oxidation of sulfide using a pencil graphite electrode modified with quercetin (PGE/QH(2)). Adsorption procedure was used for the preparation of the modified electrodes. It was observed that PGE/QH(2) showed a significant electrocatalytic activity toward sulfide oxidation. Cyclic voltammetric studies show that the peak potential of sulfide shifts from +450 mV at bare PGE to +280 mV at PGE/QH(2). The electrocatalytic currents obtained from amperometric measurements at +300 mV vs. Ag/AgCl/KClsat and at pH 8.0 BR buffer solution containing 0.1 M NH4Cl were linearly related to the concentration of sulfide. The calibration graph consisted of two linear segments of 1-20 mu M and 20-800 mu M with a detection limit of 0.3 mu M (based on 3s(b)). The proposed method was successfully applied to the determination of sulfide in waste waters and was compared with the spectrophotometric method. (C) 2012 Elsevier B.V. All rights reserved.