A functionalized sol-gel thin film modified glassy carbon electrode has been prepared for the determination of mercury. The tetrasulfide in the sol-gel matrix has a high affinity for mercury species. The chemically integrated functional groups in the sol-gel precursor ensure a high chemical and mechanical stability of the modified electrodes, and therefore a stable and reproducible analytical performance. By medium exchange anodic stripping voltammetry, this modified electrode allows reliable, low cost and interference-free determination of mercury. (C) 1999 Elsevier Science B.V. All rights reserved.