Abstract
Abstract 2, 2’-azinobis-(3-ethylbenzothiazoline-6- sulfonate acid) radical cation (ABTS•+) decolorization assay is one of the most widely used methods for analyzing the antioxidant capacity（AOC） in biological and environmental samples. A separation technique liquid chromatography combining with ABTS•+ post-column detection step has become a useful analysis approach. In this study, we present an on-line generated ABTS•+ as post-column with capillary electrophoresis for antioxidant capacity analysis. Ultraviolet (UV) irradiation at 254 nm was directly photolyed colorless ABTS to form blue-green colored ABTS•+. Furthermore, PTFE tubing coil was use to constitute a flow-through photoreactor as an on-line direct photolysis device. This system can simplify operating sequence and generate rapidly on-line ABTS•+ to reduce reverse reaction. Whether purging O2 or not, about 70% production of ABTS•+ was obtained individually both in batch and on-line direct photolysis experiments. Based on the on-line assay results, the CZE-UV/ABTS system has good precision and post-column signal was very stable at various pHs. The system can successfully separate five compounds and measure their antioxidant capacities simultaneously. The migration time was smaller than 18 min and detection limitedwas about 0.58 μM （injection sample: 84 nL）. The antioxidant capacity value of compounds shows a good agreement with reported data. In conclusion, the CZE-UV/ABTS system is feasible to determine the antioxidant capacity of real samples.