Quantification of Cu 2+ using 1,1′-oxalyldiimidazole chemiluminescence

Abstract

Emission from two different peroxyoxalate chemiluminescence (PO-CL) reaction pathways (i.e., 1,1′-oxalyldiimidazole (ODI) and bis(2,4,6-trichlorophenyl)oxalate (TCPO) CL reactions) is significantly reduced in the presence of increasing Cu 2+ concentrations. The CL intensity decrease in the ODI-CL reaction results from deactivation of the high-energy intermediate(s) by Cu 2+, whereas the apparent quenching in the TCPO-CL reaction results from both this effect and formation of Cu 2+–imidazole (ImH) complexes [Cu(ImH) n=1–4 ] 2+. Because the reaction between Cu 2+ and ImH occurs competitively with the formation of a high-energy intermediate (X) in TCPO-CL reactions, accurately determining Cu 2+ concentrations with a TCPO-CL-based system is more difficult versus an ODI-CL-based system. Using ODI-CL, the detection limit of Cu 2+ dissolved in water was determined to be 5.0 × 10 −8 M (signal:noise = 3) in a 1 cm fluorescence flow micro-cell. ODI-CL-based systems are expected to be useful for the rapid quantification of many quenchers in environmental and biological samples because the interactions between the high-energy intermediate(s) and quencher are very rapid relative to other competitive reactions.