Ru(bpy)(3)Cl-2 was used to modify the glass carbon electrodes (GCE) by oxidation and co-deposition on the electrode surface. The modified electrodes were characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). About 2.2 x 10(-9) mol Ru(bpy)(3) (2+) was immobilized on the GCE surface (phi = 4 mm). The modified GC electrodes showed stable electrochemiluminescence with tripropylamine (TPrA) as the co-reactant with a linear range from 10 to 500 mu M (R (2) = 0.999). Among the 10 amino acids tested, the modified electrode system showed selective response to arginine and lysine, indicating that the molecular structure played an important role as co-reactant. This simple and sensitive electrode modifying method when combined with flow-injection or liquid chromatography systems has the potential for amino acid analyses.