Determination of hydroxyl radical by capillary zone electrophoresis with amperometric detection

Hydroxyl radical (OH) can cause severe damage to cells and tissues. However, its analysis is very difficult for its high reactivity and very short half-life. In this paper, a simple and highly sensitive method, capillary zone electrophoresis with amperometric detection (CZE-AD) was introduced indirectly to determine OH by determining its reaction products with salicylic acid (SAL), 2,3-dihydroxybenzoic acid (2,3-DHBA) and 2,5-dihydroxybenzoic acid (2,5-DHBA). The optimum conditions of CZE-AD for the determination of 2,3-DHBA and 2,5-DHBA were explored. Under the optimum conditions, SAL, 2,3-DHBA and 2,5-DHBA could be perfectly separated within 15 min, and the linearity ranges of 2,3-DHBA and 2,5-DHBA were between 1.0×10−7 and 1.0×10−4 mol l−1. Their detection limits were as low as 2×10−8 mol l−1, which were much lower than that in CE-UV method. The method was also applied to study the free OH scavenging activity of angelica polysaccharide. The experimental results showed that this CZE-AD method was very sensitive and practical in both the determination of free OH and the evaluation of free OH scavenging activities of antioxidants.