New phenylboronic acid derivatives as enhancers of the luminol–H2O2–horseradish peroxidase chemiluminescence reaction

The preparation of three new types of phenylboronic acid derivatives and their evaluation as enhancers on the luminol–H2O2–horseradish peroxidase (HRP) chemiluminescence (CL) reaction are described. After optimizing the CL reaction conditions, the CL system was applied to the HRP determination. Among the three phenylboronic acid derivatives, i.e. 4-(4,5-diphenyl-1H-imidazol-2-yl)phenylboronic acid (DPA), 4-[4(or 5)-(4-dimethylaminophenyl)-5(or 4)-phenyl-1H-imidazol-2-yl]phenylboronic acid (DAPA) and 4-[4,5-di(2-pyridyl)-1H-imidazol-2-yl]phenylboronic acid (DPPA), DPPA was found to be the most potent enhancer. The sensitivity obtained with DPPA was about 180 times higher than that without an enhancer. The detection limit of HRP obtained with DPPA was 0.15 ng/assay (ca. 3.5 fmol), which is comparable to that with 4-iodophenol under the conditions examined. All the phenylboronic acid derivatives examined had the effect of prolonging light emission compared to 4-iodophenol. Copyright © 1999 John Wiley & Sons, Ltd.