College of Environmental & Resource Sciences, Zhejiang University, Hangzhou 310058, People's Republic of China.
Chemosphere. 2012 Nov;89(11):1376-83. doi: 10.1016/j.chemosphere.2012.05.105. Epub 2012 Jul 21.
Risk assessment of xenobiotics requires a comprehensive understanding of their transformation in the environment. As most of the transformation processes usually involve a redox reaction or a hydrolysis as the first steps of the transformation, we applied an approach that uses an electrochemical cell to investigate model "redox" reactions in aqueous solutions for environmental processes. We investigated the degradation of a variety of xenobiotics from polar to nonpolar and analyzed their degradation products by on-line coupling of electrochemistry with mass spectrometry (EC-MS). Furthermore, we evaluated possible binding reactions with regard to the generation of non-extractable residues with some model substances (catechol, phthalic acid, γ-L-Glutamyl-L-cysteinyl-glycine (GSH) and L-histidine) deduced from a natural organic matter (NOM) structure model and identified possible binding-sites. Whereas typically investigations in soil/water-systems have been applied, we used to our knowledge for the first time a bottom-up approach, starting from the chemicals of interest and different model substances for natural organic matter to evaluate chemical binding mechanisms (or processes) in the EC-MS under redox conditions. Under oxidative conditions, bindings of the xenobiotics with catechol, GSH and histidine were found, but no reactions with the model compound phthalic acid were observed. In general, no chemical binding has yet been found under reductive conditions. In some cases (i.e. benzo[a]anthracene) the oxidation product only underwent a binding reaction, whereas the xenobiotic itself did not undergo any reactions. EC-MS is a promising fast and simple screening method to investigate the environmental behavior of xenobiotics and to evaluate the potential risks of newly synthesized substances.
外源化学物的风险评估需要全面了解其在环境中的转化。由于大多数转化过程通常涉及氧化还原反应或水解作为转化的第一步，因此我们采用了一种方法，使用电化学池来研究环境过程中模型“氧化还原”反应。我们研究了各种从极性到非极性的外源化学物的降解，并通过电化学与质谱（EC-MS）的在线偶联分析了它们的降解产物。此外，我们还评估了一些模型物质（儿茶酚、邻苯二甲酸、γ-L-谷氨酰-L-半胱氨酸-甘氨酸（GSH）和 L-组氨酸）与天然有机物（NOM）结构模型推断的非提取残留物生成的可能结合反应，并确定了可能的结合部位。虽然通常在土壤/水系统中进行调查，但我们首次使用自下而上的方法，从感兴趣的化学物质和不同的天然有机物模型物质开始，评估在氧化还原条件下 EC-MS 中的化学结合机制（或过程）。在氧化条件下，发现外源化学物与儿茶酚、GSH 和组氨酸结合，但未观察到与模型化合物邻苯二甲酸的反应。一般来说，在还原条件下尚未发现化学结合。在某些情况下（例如苯并[a]蒽），氧化产物仅发生结合反应，而外源化学物本身未发生任何反应。EC-MS 是一种很有前途的快速简便的筛选方法，可用于研究外源化学物的环境行为，并评估新合成物质的潜在风险。
