Electrochemical Sensor Sytem for Trace Silicic Acid Analysis

A highly sensitive voltammetric detection of silicic acid (SA), the main chemical species of dissolved silica in sea water, is described. The protocol relies on a fast square-wave voltammetric measurement of the decreased molybdenum stripping signal due to the formation of silicomolybdate complex. The cathodic stripping experiments were performed at the mercury film electrodes using HCl-KCl (pH 1.6) buffer solution. Different ligands, pH, ligand concentration, deposition potential and accumulation time were evaluated. Under the optimal conditions, a linear response is observed over the 50 - 400 µg/L SA concentration range with a detection limit of 2 µg/L. A highly stable response, with a relative standard deviation (RSD) of 4.8%, is observed for 10 repetitive measurements. Such electrochemical approach offers great promise for a simple, rapid, sensitive on-site or in situ real-time detection of SA.