Two new electrochemiluminescence (ECL) systems, the Ru(bpy)(3)(2+)/formaldehyde system and the Ru(bpy)(3)(2+)/formic acid system, have been reported. Intense ECL was observed from Ru(bpy)(3)(2+) in the presence of formaldehyde or formic acid at glassy carbon electrodes, but not at platinum and gold electrodes. The ECL reactions may involve the oxidation of formaldehyde and formic acid by electrogenerated OH. to form the strong reducing intermediates (CHO)-C-center dot and CO2-center dot that react with Ru(bpy)(3)(3+) to emit light. The ECL intensity increases linearly with the formaldehyde or formic acid concentration over the range of concentration of 3 mu M-1 mM. The detection limit is 1 mu M for formaldehyde and formic acid. (C) 2010 Elsevier B.V. All rights reserved.