In this paper, oxidation of D-glucose on RuCl2(azpy)(2) (azpy = 2-phenylazopyridine), as electrochemical mediator is studied. The complexes RuCl2(azpy)(2) were prepared according to literature procedures with some modifications. Two isomers (E-Z or γ-RuCl2(azpy)(2) and E-E or δ-RuCl2(azpy)(2)) were isolated. Each isomer and the crude were investigated electrochemically by immobilizing them with a Nafion/water solution on carbon Toray (CT) as supporting electrode. The voltammetric investigations were in fact used to determine the optimized oxidation potentials, which were helpful to carry out long-term electrolyses of glucose in carbonate buffer. High value products such as 2-ketogluconic and gluconic acids were obtained. The comparison of the results between the crude complex and the two isomers showed that γ-RuCl2(azpy)(2) was the most active catalyst. © 2004 Elsevier Ltd. All rights reserved.