Selectivity of novel chemiluminescence reagents towards various pharmaceuticals and controlled drugs

Iridium(III) complexes are viewed as promising alternatives to the widely used tris(2,2?-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) for chemiluminescence (CL) detection, but they generally display poor water-solubility. In this research, various water-soluble iridium(III) complexes were investigated for CL detection with selected pharmaceuticals and illicit drugs. Cerium(IV) is commonly used for the chemical oxidation of [Ru(bpy)3]2+. It has also been used in CL reactions with some iridium(III) complexes, but examination of their redox potentials has revealed that they will not react with this oxidant. An alternative reaction pathway must occur for the observed CL with these iridium(III) complexes. It was determined through spectroscopic and CL techniques that energy transfer, possibly from an electronically excited cerium(III)* species, is a viable mechanism for the observed CL from the iridium(III) luminophores. An alternative, photoinduced chemical oxidation method, capable of generating the oxidised iridium(IV) species, was examined, however, this strategy demonstrated similarly poor results for CL detection. The photoinduced oxidation of [Ru(bpy)3]2+, however, produced much greater CL intensities for certain analytes and was then applied to post-column CL detection for the high performance liquid chromatography (HPLC) determination of piperazine stimulants.