Electrogenerated Chemiluminescence from Tris(2,2-bipyridyl)ruthenium(II) Immobilized in Titania-Perfluorosulfonated Ionomer Composite Films

Electrochemical behavior and electrogenerated chemiluminescence (ECL) of tris(2,2ʹ-bipyridyl)ruthenium(II) (Ru(bpy)3^2+) immobilized in sol-gel-derived titania (TiO2)-Nafion composite films coated on a glassy carbon electrode have been investigated. The electroactivity of Ru(bpy)3^2+ ion exchanged into the composite films and its ECL behavior were strongly dependent upon the amount of Nafion incorporated into the TiO2-Nafion composite films. The ECL sensor of Ru(bpy)3^2+ immobilized in a TiO2-Nafion composite with 50% Nafion content showed the maximum ECL intensities for both tripropylamine (TPA) and sodium oxalate in 0.05 M phosphate buffer solution at pH 7. Detection limits were 0.1 (mu)M for TPA and 1.0 (mu)M for oxalate (S/N = 3) with a linear range of 3 orders of magnitude in concentration. The present ECL sensor showed improved ECL sensitivity and long-term stability, as compared to the ECL sensors based on pure Nafion films. The present Ru(bpy)3^2+ ECL sensor based on TiO2-Nafion (50%) composite films was applied as an HPLC detector for the determination of erythromycin in human urine samples. The present Ru(bpy)3^2+ ECL sensor was stable in the mobile phase containing a high content of organic solvent (30%, v/v), in contrast to a pure Nafion-based Ru(bpy)3^2+ ECL sensor. The detection limit for erythromycin was 1.0 (mu)M, with a linear range of 3 orders of magnitude in concentration.