School of Energy and Environmental Engineering, University of Science and Technology Beijing, Xueyuan Road No.30, Haidian District, Beijing 100083, PR China; Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Permoserstraße15, Leipzig 04318, Germany.
Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Permoserstraße15, Leipzig 04318, Germany.
Chemosphere. 2018 Dec;212:133-142. doi: 10.1016/j.chemosphere.2018.08.034. Epub 2018 Aug 10.
Tributyl phosphate (TBP) belongs to the group of trialkyl substituted organophosphate esters. Its chemical reactivity depends on the stability of various chemical bonds. TBP was used as a model compound for the development of a concept using stable isotope fractionation associated with bond cleavage reactions for better understanding the fate of TBP in the environment. Carbon isotope enrichment factors (ε) of TBP hydrolysis were found to be pH dependent (-3.8 ± 0.3‰ at pH 2, -4.6 ± 0.5‰ at pH 7, -2.8 ± 0.1‰ at pH 9, no isotope fractionation at pH 12), which is in accordance with the mode of a S2 hydrolytic bond cleavage. Hydrogen isotope fractionation was negligible as no H bond cleavage is involved during hydrolysis. The apparent carbon kinetic isotope effect (AKIE) ranged from 1.045 to 1.058. In contrast to hydrolysis, both carbon and hydrogen isotope fractionation were observed during radical oxidation of TBP by OH and SO, yielding ε from -0.9 ± 0.1‰ to -0.5 ± 0.1‰ and ε from -20 ± 2‰ to -11 ± 1‰. AKIE and AKIE varied from 1.007 to 1.011 and from 1.594 to 2.174, respectively. The correlation of H and C isotope fractionation revealed Λ values ranging from 17 ± 1 to 25 ± 6. Results demonstrated that the correlation of H and C isotope fractionation of TBP allowed to identify radical reactions and to distinguish them from hydrolysis. The presented dual isotope analysis approach has diagnostic value for characterizing the chemical transformation of TBP in the environment.
磷酸三丁酯（TBP）属于三烷基取代的有机磷酸酯类。其化学反应性取决于各种化学键的稳定性。TBP 被用作一种模型化合物，用于开发一种利用与键断裂反应相关的稳定同位素分馏的概念，以更好地了解 TBP 在环境中的归宿。TBP 水解的碳同位素富集因子（ε）发现与 pH 值有关（在 pH 值为 2 时为-3.8±0.3‰，在 pH 值为 7 时为-4.6±0.5‰，在 pH 值为 9 时为-2.8±0.1‰，在 pH 值为 12 时没有同位素分馏），这与 S2 水解键断裂的模式一致。由于水解过程中不涉及 H 键断裂，因此氢同位素分馏可以忽略不计。表观碳动力学同位素效应（AKIE）范围为 1.045 至 1.058。与水解不同，TBP 被 OH 和 SO 自由基氧化时，观察到碳和氢同位素分馏，ε 值范围为-0.9±0.1‰至-0.5±0.1‰，ε 值范围为-20±2‰至-11±1‰。AKIE 和 AKIE 分别为 1.007 至 1.011 和 1.594 至 2.174。氢和碳同位素分馏的相关性揭示了 Λ 值范围为 17±1 至 25±6。结果表明，TBP 的氢和碳同位素分馏的相关性允许识别自由基反应，并将它们与水解区分开来。所提出的双同位素分析方法对表征 TBP 在环境中的化学转化具有诊断价值。
