Highly oxidized glassy carbon and other metal (gold and platinum) electrode surfaces were generated by applying 2.0 V vs. SCE for 600 s in pH 7 solution. The effects of oxidation on the functional, physical, and chemical characteristics of the electrodes went beyond the usual conditioning of such electrode surfaces through cycling to slightly beyond the medium decomposition potentials. The oxidized electrodes showed enhanced electrochemical activities and lower background currents. Besides cleaning the surface of contaminants introduced in the polishing stage of electrode preparation, application of such high potentials for an extended time interval changed the chemical nature of the glassy carbon surface itself. The chemical changes influenced the electro-oxidation reaction of bio-molecules such as ascorbic acid and uric acid but did not influence the reaction of the ferri- and ferrocyanide system. As a result the biological molecules (uric acid and ascorbic acid) were detected using an electrochemical method individually and simultaneously without the necessity for any electron relay complex. (C) 2004 Elsevier B.V. All rights reserved.