Key Laboratory of Biogeology and Environmental Geology, MOE & School of Environmental Studies, China University of Geosciences, Wuhan 430074, China.
Anal Bioanal Chem. 2011 Jan;399(1):421-8. doi: 10.1007/s00216-010-4320-5. Epub 2010 Oct 27.
Metronidazole is a nitroimidazole antibiotic derivative used in humans against anaerobic bacteria and protozoa. In light of the recent detection of metronidazole in hospital wastes, sewage treatment plants, and surface waters, along with its known sensitivity toward photolytical degradation, this study aimed to model the photolysis in environmental waters by sunlight as a natural attenuation process. To this end, the degradation of metronidazole in a photoreactor simulating solar radiation (Suntest CPS) was compared in five different aqueous matrices: deionized water, artificial freshwater (AFW), AFW supplemented with nitrate (5 mg/L), AFW containing humic acids, and AFW with both nitrate and humic acids. Irrespective of the test medium, the degradation of the metronidazole solutions (10 and 0.02 mg/L) was found to follow pseudo-first-order kinetics. Degradation rates were dependant on the matrix, with humic acids causing a two to threefold decrease in the rate constants while the presence of nitrate had no marked effect on the kinetics. Therefore, the direct photolysis of metronidazole was apparently attenuated through a filter effect of humic acids. Screening of the irradiated water samples by ultra performance liquid chromatography/quadrupole time-of-flight mass spectrometry allowed separation and characterisation of four principal phototransformation products of the antibiotic. The high-resolution MS data pointed to the formation of two rearrangement products (C(6)H(10)N(3)O(3)) isobaric with metronidazole, a third product deriving from the elimination of NO from the nitro group (C(6)H(11)N(2)O(2)), and a fourth unidentified degradate with a likely elemental composition of C(5)H(10)N(3)O.
甲硝唑是一种用于治疗人类厌氧菌和原生动物感染的硝基咪唑类抗生素。鉴于甲硝唑最近在医院废物、污水处理厂和地表水等环境中被检测到，以及其对光解降解的已知敏感性，本研究旨在通过模拟太阳光的光解来模拟环境水中的自然衰减过程。为此，在模拟太阳辐射的光反应器（Suntest CPS）中比较了甲硝唑在五种不同水基质中的降解情况：去离子水、人工淡水（AFW）、添加硝酸盐（5mg/L）的 AFW、含有腐殖酸的 AFW 以及同时含有硝酸盐和腐殖酸的 AFW。无论测试介质如何，甲硝唑溶液（10 和 0.02mg/L）的降解均遵循拟一级动力学。降解速率取决于基质，腐殖酸使速率常数降低了两到三倍，而硝酸盐的存在对动力学没有明显影响。因此，甲硝唑的直接光解显然通过腐殖酸的过滤效应而减弱。通过超高效液相色谱/四极杆飞行时间质谱对辐照水样进行筛选，可分离并鉴定抗生素的四个主要光转化产物。高分辨率 MS 数据表明形成了两种重排产物（C(6)H(10)N(3)O(3)），与甲硝唑等摩尔，一种来自硝基中 NO 消除的产物（C(6)H(11)N(2)O(2)），以及第四种未知降解产物，其可能的元素组成为 C(5)H(10)N(3)O。
