Influence of imidazole and bis(trichlorophenyl) oxalate in the oxalyldiimidazole peroxyoxalate chemiluminescence reaction

The complex role of imidazole when used as a catalyst in the bis(2,4,6-trichlorophenyl) oxalate (TCPO) peroxyoxalate chemiluminescence (PO-CL) reaction is explained by the transient formation and subsequent degradation of 1,1'-oxalyldiimidazole (ODI). When ODI was used directly as PO-CL reagent, the stability was improved by addition of TCPO as an ''imidazole sponge'', since ODI is rapidly decomposed in the presence of imidazole. in this way, the imidazole-catalyzed degradation of ODI was hindered efficiently. The stability of ODI was also influenced by the storage vessel material. Polymeric bottles were found to be more suitable than glass containers, A comparison was made between the traditionally used reagent TCPO/imidazole (mixed on-line for formation of ODI) and the new reagent combination ODI-TCPO (premixed) with respect to sensitivity, noise, and background.