Determination of Hg(II) by Thiourea Grafted Chitosan Modified Carbon Paste Electrode: Reversibility and Electrochemical Parameters Studies

Mercury(II) was sensitively detected in acidic solutions using chitosan (Cts) reinforced by grafting Thiourea (TU). In order to validate our developed method, the characteristics of the carbon paste electrode (CPE) modified with (TU-gt-Cts) were investigated by several electrochemical techniques, and the surface parameters were determined. Cyclic voltammetry (CV) analysis were realized in the presence of [Fe(CN)6]3−/4− and KCl as a redox probe and the effectives surfaces area (A) were calculated. Electrochemical impedance spectroscopy (EIS) measurements indicated low interfacial charge transfer resistance at the (TU-gt-Cts) modified electrode. The study of the scan rate effect denotes that the electrochemical system presented a diffusion controlled process happened in conjunction with a quasi-reversible electron transfer reaction. Electrochemical parameters of mercury on the surface of (TU-gt-Cts/CPE) were determined with a chronoamperometry (CA) method as D=2.22×10-5 cm2s-1 and k0=1.15×10-3 cms-1, for the diffusion coefficient and standard rate constant of electron transfer respectively. The square wave anodic striping voltammetry (SWASV) was checked as a sensitive detection method. Under the optimized chemical and instrumental parameters, the stripping peak current was linear to the Hg(II) concentration in the ranges of 5.0×10-9 to 1.0×10–6 molL–1 and from 1.0×10–6 to 5.0×10–6 molL–1 with a detection limit (LOD) of 1.61×10–9 molL–1. The studied sensor was successfully applied for Hg(II) detection in tap and seawater with adequate recoveries.