Catalytic behaviour of iron(II)-oxime complexes in the chemiluminescence reaction of luminol with hydrogen peroxide

Abstract

Chemiluminescence produced by the catalytic effect of iron(II)-oxime complexes on the oxidation of luminol by hydrogen peroxide was studied. This is a very fast chemiluminescence reaction and the emission spectrum is similar to that of peroxidase-catalysed chemiluminescence. Different kinds of iron(II)-oxime complexes were compared and it was found that the symmetrical dioxime complex (four nitrogen ligands) has a higher catalytic activity than the asymmetric monooxime complex (two nitrogen and two oxygen ligands). The presence of EDTA can greatly accelerate the chemiluminescence reaction, which was considered to be a result of the formation of a mixed-ligand complex. Other homologues of EDTA were tested and showed different degrees of enhancement. Optimum conditions for the chemiluminescence reactions were examined. Combined with a flow-injection technique, trace amounts of hydrogen peroxide (2 X 10 −7 −1 X 10 −4 M) and, using glucose oxidase, glucose (0.79–160 μg ml −1) can be determined by using the iron(II)-dimethylglyoxime complex as a typical catalyst. The detection limit of hydrogen peroxide was 1.3 X 10 −8 M. The relative standard deviation was 1% for the determination of 2 X 10 −7 M H 2O 2 ( n = 11). The feasibility of utilizing the proposed method for the determination of glucose in human serum was examined.