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/KCl(sat) and at pH 8.0 BR buffer solution containing 0.1M NH(4)Cl were linearly related to the concentration of sulfide. The calibration graph consisted of two linear segments of 1-20 μM and 20-800 μM with a detection limit of 0.3 μM (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.