Chemiluminescence of ABEI-labelled IgG triggered by the N-chloramine-H2O2-p-iodophenol system

Light is emitted in systems containing N-chloramines or hypochlorite, H2O2 and N-(4-aminobutyl)-N-ethylisoluminol (ABEI). The emission is enhanced by 4-iodophenol (PIP) in alkaline solution (1 mol/L NaOH), while at lower pH r ange (9-11) PIP is not only inactive but also its presence reduces chemilum inescence (CL) of the monochloramine-H2O2-ABEI system to the background. Tw o procedures for ABEI-labelled IgG assays were developed, with PIP in 1 mol /L NaOH and without PIP at pH 11, and the standard curves of free ABEI in t hese conditions were examined. We suggest also that the oxidative deaminati on of taurine chloramine leads to the formation of the various carbonyl der ivatives and their formation is accelerated in the presence of H2O2, especi ally in less alkaline solutions (pH ii). Moreover, the formation of enol fo rms of aldehydes in assay buffers was observed. The yield of the phenoxy ra dical mediators of ABEI oxidation and the pi-I-dependent H2O2:HO2 ratio see ms to be decisive for the overall CL in the system examined. The main advan tage of this method is that CL does not need precise timing of measurements and assays can be performed over a long period of time (hours) using a pla te luminometer. Copyright (C) 1999 John Wiley & Sons, Ltd.