Electrooxidation of thiocyanate on the copper-modified gold electrode and its amperometric determination by ion chromatography

Abstract

Cyclic voltammetry was used to investigate the electrochemical behavior of an Au/Cu electrode towards the electrooxidation of thiocyanate ion in alkaline medium. The effects of pH, copper loading, scan rate and applied potential on the electrocatalytic oxidation of thiocyanate have been investigated. Flow injection experiments and ion-chromatography (IC) were performed to characterise the electrode as an amperometric sensor for the thiocyanate determination. The effects of carbonate concentration and common interferents on the retention time were also estimated. The electrode stability, precision, limit of detection and linear range were evaluated at a constant applied potential of 0.7 V vs. Ag/AgCl. Calibration plots, obtained in IC, were linear from 1.0 to 195 µM (correlation coefficient of 0.9984). The detection limit (LOD) was 0.5 µM (29 ppb) in a 50 µl injection. An example of analytical application, which includes the IC separation and detection of thiocyanate ion present in human urine, is given.