This paper describes the performance of an amperometric sensor for thiol detection. The sensor was designed based on a Prussian blue (PB) glassy carbon (GC) electrode. Prussian blue was chemically deposited onto the glassy carbon electrode by a dropletting method. Thiol compounds were detected at the PB-modified GC electrode by electro oxidation. A PB-modified glassy carbon electrode was applied to detect thiol at an applied potential of +0.25 V versus the Ag/AgCl electrode. This sensor showed an excellent electrochemical response for thiol compounds below pmol level with high sensitivity and selectivity and short response time. In the case of aminoethanethiol, the sensor showed a wide linearity range with RSDs < 4% for the whole analyses, which reflected the highly reproducible sensor performance. The optimal conditions were investigated. By using the optimized conditions, the detection limit was found to 0.4 mu M for aminoethanethiol (based on S/N= 3). (C) 2006 Elsevier B.V. All rights reserved.