Enhancing the sensitivity towards iodide detection by coupling SECM and an EC acute accent catalytic mechanism

In this work, a gold conventional sized electrode (r = 3 mm) and a gold microelectrode (r = 12.5 mu m) were employed to investigate the EC' mechanism involving the anodic oxidation of iodide in the presence of the non-redox-active species thiosulfate. A significant anodic current increase, due to the electrocatalytic process, was noticed in cyclic voltammograms recorded in an iodide solution in the presence of thiosulfate when compared to iodide solution only, at the same experimental conditions. Aiming to enhance the sensitivity of the electro-analytical method towards iodide detection, Scanning Electrochemical Microscopy (SECM) was employed to confine reactants and products in a thin-layer cell defined by the solution region between the microelectrode tip and a Au substrate. Very low iodide concentrations, in the range of a 1-10 mu mol/L, can be detected at a short tip-substrate distance, and the method was validated by measuring the analyte content in a synthetic urine sample.