A two-step sol–gel technique was used here to prepare a carbon ceramic electrode modified with nafion and [Ru(bpy)(tpy)Cl]PF6. Thisinvolves two steps: first, forming a bulk-modified carbon ceramic electrode with nafion, and then immersing the electrode into a Ru-complexsolution (electroless deposition) for a short period of time (5–25s). Cyclic voltammograms of the resulting surface-modified carbon ceramicelectrode show stable and a well-defined redox couple due to Ru(II)/Ru(III) system with surface-confined characteristic. l-Cysteine (CySH)has been chosen as a model to elucidate the electrocatalytic ability of Ru-complex nafion sol–gel composite electrode. Not only the modifiedelectrode shows excellent catalytic activity toward l-cysteine electrooxidation in pH range 3–9, but the antifouling effect of nafion film alsoincreases the reproducibility of results in comparison with CCE modified with homogeneous mixing of graphite powder and Ru-complex(one step sol–gel method). Under the optimized conditions in amperometry method, the concentration calibration range, detection limit andsensitivitywere0.1–100 M,20 nMand 50nA/M, respectively.The advantagesofthis modified electrode aregood reproducibility, excellentcatalytic activity, simplicity of preparation and especially its antifouling properties towards l-cysteineand its oxidation products. Additionally,it is promising as a detector in flow system or chromatography systems.© 2004 Elsevier B.V. All rights reserved.