Quantification of Cu2+ using 1,1′-oxalyldiimidazole chemiluminescence

Emission from two different peroxyoxalate chemilummescence (PO-CL) reaction pathways (i.e., 1,1'-oxalyldiimidazole (ODI) and bis(2,4,6trichlorophenyl)oxalate (TCPO) CL reactions) is significantly reduced in the presence of increasing Cu2+ concentrations. The CL intensity decrease in the ODI-CL reaction results from deactivation of the high-energy intermediate(s) by Cu2+, whereas the apparent quenching in the TCPO-CL reaction results from both this effect and formation of Cu2+-imidazole (ImH) complexes [Cu(ImH)(n = 1-4)](2+). Because the reaction between Cu2+ and ImH occurs competitively with the formation of a high-energy intermediate (X) in TCPO-CL reactions, accurately determining Cu2+ concentrations with a TCPO-CL-based system is more difficult versus an ODI-CL-based system. Using ODI-CL, the detection limit of Cu2+ dissolved in water was determined to be 5.0 x 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. (c) 2006 Elsevier B.V. All rights reserved.