Electrogenerated chemiluminescence of tris(2,2′-bipyridyl) ruthenium(II) immobilized in humic acid-silica-poly(vinyl alcohol) composite films

In this paper, we report the first attempt to use humic acid (HA) as modifiers to prepare the organic-inorganic hybrid modified glassy carbon electrodes based on HA-silica-PVA (poly(vinyl alcohol)) sol-gel composite. Electroactive species of tris(2,2 '-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) can easily incorporate into the HA-silica-PVA films to form Ru(bpy)(3)(2+) modified electrodes. The amount of Ru(bpy)(3)(2+) incorporated in the composite films strongly depends on the amount of HA in the hybrid sol. Electrochemical and electrogenerated chemiluminescence (ECL) of Ru(bpy)(3)(2+) immobilized in HA-silica composite films coated on a glassy carbon electrode have been studied with tripropylamine (TPA) as the coreactant. The analytical performance of this modified electrode was evaluated in a flow injection analysis (FIA) system with a homemade flow cell. The as-prepared electrode showed good stability and high sensitivity. The detection limits (S/N= 3) were 0.050 mu mol L-1 for TPA and 0.20 mu mol L-1 for oxalate, and the linear ranges were from 0.10 mu mol L-1 to 1.0 mmol L-1 for TPA and from 1.0 mu mol L-1 to 1.0 mmol L-1 for oxalate, respectively. The resulting electrodes were stable over two months.