二甲亚砜捕获-高效液相色谱测定天然水体中羟基自由基的光化学生成

Determination of photogenerated hydroxyl radicals in natural water by high performance liquid chromatography after trapping with dimethyl sulfoxide

利用二甲亚砜捕获羟基自由基定量生成甲醛,甲醛与1,3-环己二酮和氨衍生反应,衍生产物在400 nm的激发波长下,在460 nm处具有特征荧光,建立了一个新的高效液相色谱分离、荧光检测水体中光学反应产生的羟基自由基的方法.考察了捕获剂用量、酸度、温度、时间以及衍生试剂用量对羟基自由基测定的影响,在优化的实验条件下,该方法对羟基自由基的定量下限为0.066μmol·L-1.采用建立的方法对湖水、海水以及湿地水在氙灯模拟光源以及太阳光下羟基自由基光化学生成进行了初步研究,表明太阳光照下羟基自由基的生成速率约为氙灯光照下羟基自由基生成速率的两倍以上,说明羟基自由基在实际自然条件下的生成速率有可能被低估.天然水体中的羟基自由基的生成与水体成分密切相关,由铁和可溶性有机质(DOM)光照产生羟基自由基的机理较为复杂,DOM和铁的相互作用对天然水体中羟基自由基的光化学生成影响有待于进一步研究.

Hydroxyl radicals photochemically generated in natural water play an important role in the transformation of pollutants. A high performance liquid chromatography method for the determination of hydroxyl radicals was developed, based on trapping hydroxyl radicals with dimethyl sulfoxide to generate formaldehyde quantitatively. Formaldehyde then reacted with 1,3-cyclohexanedione and ammonia to producea derivative of formaldehyde, which was separated and analyzed by HPLC with fluorescence detector. Factors influencing the trapping of hydroxyl radical and derivation, such as trapping and derivatization reagent amount, pH, temperature and time, were investigated. Under the optimized condition, the lower limit at quantification reached 0.066 μmol·L-1. The method was applied to the determination of hydroxyl radicals generated in typical natural water （lake, sea and wetland water） under sunlight and Xenon lamp. The results showed that the photochemical generation of hydroxyl radicals under the natural condition was possibly underestimated. The generation of hydroxyl radical was closely related to the constituent in natural water, especially the interaction between DOM and iron.