Analysis of antioxidants by microchip capillary electrophoresis with chemiluminescence detection based on luminol reaction

A microchip including two micro-channels for electrophoretic flow and one micro-flow line for pumping flow was designed for the analysis of antioxidants by microchip capillary electrophoresis with a chemiluminescence detection system. The chemiluminescence reaction of luminol with hydrogen peroxide in the presence of Cu(II) catalyst was adopted in the present system, where active oxygen species, such as superoxide radical anions, generates. Nitroblue tetrazolium, superoxide dismutase, and catechin (catechin mixture from green tea) were analyzed as model analytes of antioxidants using the system. Negative peaks from baseline formed by the chemiluminescence reaction were observed based on reaction between active oxygen (superoxide radical anion) and antioxidants (analytes). The components of analytes mixture, nitroblue tetrazolium and superoxide dismutase, were well separated and detected within ca. 2 min. Catechin was also detected around 2 min, resulting in a response curve over the range of 0.1–1 mM. The amounts of catechin in the real samples of commercial green tea beverages were successfully determined.