Capillary electrophoresis with gold nanoparticles enhanced electrochemiluminescence for the detection of roxithromycin

Tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy)32+)–roxithromycin based electrochemiluminescence (ECL) was enhanced greatly by gold nanoparticles 10 nm in diameter. Capillary electrophoresis (CE) was coupled with the resultant ECL system as a detector for roxithromycin. This ECL emission is explained by the coreactant mechanism where roxithromycin behaves as a coreactant to generate strong reducing species and gold nanoparticles act as “floating nanoelectrodes”. The reaction of Ru(bpy)33+ with the generated strong reducing species on the Pt working electrode as well as on “floating nanoelectrodes” releases Ru(bpy)32+*, resulting in enhancement of ECL emission. The selectivity of this detection system towards roxithromycin was examined by CE. Under the optimized conditions, the intensity of ECL emission varies linearly with the concentration of roxithromycin from 24 nM to 0.24 mM. The detection limit is 8.4 nM, while without adding gold nanoparticles it is only 84 nM. The detection of roxithromycin in pharmaceutical and urine samples was also performed by the proposed CE–ECL method.