Lophine derivatives and analogues as new phenolic enhancers for the luminol–hydrogen peroxide–horseradish peroxidase chemiluminescence system Original Research Article

Of nine compounds tested, two new phenolic compounds, 2-(4-hydroxyphenyl)-4,5-diphenylimidazole (HDI) and 2-(4-hydroxyphenyl)-4,5-di(2-pyridyl)imidazole (HPI), were found to act as potent enhancers of the peroxidase-catalyzed chemiluminescence (CL) reaction of luminol with hydrogen peroxide. The CL reaction conditions were optimized and their enhancement characteristics were compared with that of 4-iodophenol. HDI and HPI produced a stronger enhancement of the CL with the effect of prolonging the light emission. Under the optimum conditions, the detection limits (2 × blank signal) of horseradish peroxidase (HRP) obtained with HDI and HPI were ca. 800 and 430 amol, respectively. Both of the developed enhancers have advantages over 4-iodophenol with respect to the sensitivity in determining HRP and stability on storage.