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 15min, and the linearity ranges of 2,3-DHBA and 2,5-DHBA were between 1.0×10^-7 and 1.0×10^-4mol 1^-1. Their detection limits were as low as 2×10^-8mol 1 ^-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.