Evaluation of electrogenerated chemiluminescence from a neutral Ir(III) complex for quantitative analysis in flowing...

Though recently Ir(III) complexes have attracted much interest in electrochemiluminescent (ECL) analysis due to their high emission in various wavelengths, there were a few studies reported on its analytical applications. In this study, we evaluate the ECL from (pq)(2)Ir(acac) (pq = 2-phenylquinolate, acac = acetylacetonate) for the use in flow injection analysis. An aqueous solution of the analyte and (pq)(2)Ir(acac) passes through the reaction/observation cell, and then ECL reaction is generated by electrochemical initiation on the analyte and (pq)(2)Ir(acac). Tri-n-propylamine (TPrA) is used as a representative analyte for evaluation. Additionally, a comparison is made of the relative ECL intensities obtained for a variety of analytes including oxalate, amino acids, aliphatic amines, and NADH. The (pq)(2)Ir(acac) produces efficient ECL upon TPrA exhibiting the limit of detection of 5 nM with a linear range of 3 orders of magnitude in concentration whereas 20 nM is observed in the conventional Ru(bpy)(3)(2+) system. It shows particular sensitivity advantages for oxalate, proline, and tartaric acid. The ECL generation upon various analytes proposes direct applicability of (pq)(2)Ir(acac) as a post-column detection tool.