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 bismuth film electrode 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 mu g L(-1) SA concentration range with a detection limit of 2 mu g L(-1). A highly stable response, with a relative standard deviation (RSD) of 4.8%, is observed for 10 repetitive measurements. Such an electrochemical approach offers great promise for a simple, rapid, sensitive, and on-site or in situ real-time detection of SA. (c) 2010 Elsevier B.V. All rights reserved.