Highly selective and sensitive iodide sensor based on carbon paste electrode modified with nanosized sulfate-doped α-[formula omitted

Abstract

Sulfate-doped α-Fe2O3 nanoparticles-modified carbon paste electrode (CPE) was demonstrated to be an efficient and highly selective sensor for iodide concentration determination. The detection process was characterized by studying the redox behavior of I2/I− couple at both modified and unmodified carbon paste electrodes via cyclic voltammetry and electrochemical impedance spectroscopy. It was shown that α-Fe2O3-incorporated CPE is better than bare CPE for I− oxidation as well as I2 reduction. However, Sulfate-doped α-Fe2O3-CP electrode led to the highest efficiency for I− oxidation among all examined electrode, suggesting that modification of the hematite with sulfate improves the electrocatalytic performance of hematite for iodide ion oxidation. The effect of electrode composition (sulfated α-Fe2O3, carbon, binder) as well as electrochemical determination conditions (including pH and accumulation time) on the response of Sulfate-doped α-Fe2O3-CPE was investigated and the optimum conditions were chosen. A good linear correlation was obtained between iodide concentration and cyclic voltammetry response, in a concentration range of 2.5 × 10−7 to 1.5 × 10−3 mol L−1. The detection limit of the developed sensor for iodide ion was calculated to be 0.1 μmol L−1 (S/N = 3) for an accumulation time of 15 min. The relative standard deviation (RSD) was found to be 3.5% (n = 5). Determination of iodide by the sensor in real samples, such as sea water and soil, led to satisfactory results.