Very fast peroxyoxalate chemiluminescence

Peroxyoxalate chemiluminescence (PO-CL) detection offers an advantage in ch romatographic detection, by the virtue of its multiple unique selectivities and high sensitivity. However, many of the analytical separation technique s available today require observation times in the millisecond range to pre serve the band resolution, and as the reaction kinetics of the PO-CL reacti on is considerably slower, extra flow elements are needed to observe the re action in a time window at maximum emission intensity. Since these flow ele ments increase the complexity of the system and contribute to band-broadeni ng, the rational way to adapt PO-CL detection to miniaturised separation sy stems is to speed up the reaction, so that it emits an initial burst of lig ht within the acceptable detection time-frame. Although this may result in a lower overall quantum yield, the actual detection sensitivity could be eq ual to, or better than slower PO-CL systems. By making careful selections o f oxalic reagent and catalyst(s) the reaction can be fine-tuned to maximise the intensity. In this work, the time-dependent light emission from the re action of bis(2,4,6-trichlorophenyl)oxalate (TCPO) was studied under the ca talytic influence of imidazole, 1,2,4-triazole, 4-dimethylaminopyridine (DM AP), and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) in acetonitrile. Both D MAP and DBU accelerated the reaction substantially, but the best combinatio n of reaction speed and intensity was found for a mixture of 0.5 mM DBU and 5 mM 1,2,4-triazole, which reached its maximum emission after only 40 ms a nd had an emission intensity comparable to that seen with 5 mM imidazole as catalyst. (C) 1999 Elsevier Science B.V. All rights reserved.