†Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ, 04318 Leipzig, Saxony, Germany.
‡Institute for Ecopreneurship, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, 4132 Muttenz, Basel-Landschaft, Switzerland.
Environ Sci Technol. 2015 May 19;49(10):6029-36. doi: 10.1021/acs.est.5b00367. Epub 2015 May 11.
Carbon isotope fractionation of sulfamethoxazole (SMX) during biodegradation by Microbacterium sp. strain BR1 (ipso-hydroxylation) and upon direct photolysis was investigated. Carbon isotope signatures (δ(13)C) of SMX were measured by LC-IRMS (liquid chromatography coupled to isotope ratio mass spectrometry). A new LC-IRMS method for the SMX metabolite, 3-amino-5-methylisoxazole (3A5MI), was established. Carbon isotope enrichment factors for SMX (ε(C)) were -0.6 ± 0.1‰ for biodegradation and -2.0 ± 0.1‰ and -3.0 ± 0.2‰ for direct photolysis, at pH 7.4 and pH 5, respectively. The corresponding apparent kinetic isotope effects (AKIE) for ipso-hydroxylation were 1.006 ± 0.001; these fall in the same range as AKIE in previously studied hydroxylation reactions. The differences in SMX and 3A5MI fractionation upon biotic and abiotic degradation suggest that compound specific stable isotope analysis (CSIA) is a suitable method to distinguish SMX reaction pathways. In addition, the study revealed that the extent of isotope fractionation during SMX photolytic cleavage is pH-dependent.
研究了微生物菌 BR1 菌株（羟化作用）生物降解磺胺甲恶唑（SMX）和直接光解过程中 SMX 的碳同位素分馏。通过 LC-IRMS（液相色谱-同位素比质谱）测量 SMX 的碳同位素特征（δ(13)C）。建立了一种新的用于 SMX 代谢物 3-氨基-5-甲基异恶唑（3A5MI）的 LC-IRMS 方法。在 pH 值为 7.4 和 pH 值为 5 时，SMX 的碳同位素富集因子（ε(C)）分别为-0.6 ± 0.1‰和-2.0 ± 0.1‰和-3.0 ± 0.2‰，用于直接光解。相应的 ipso-羟基化表观动力学同位素效应（AKIE）为 1.006 ± 0.001；这些值与先前研究的羟基化反应中的 AKIE 值处于相同范围。生物和非生物降解过程中 SMX 和 3A5MI 分馏的差异表明，化合物特异性稳定同位素分析（CSIA）是区分 SMX 反应途径的合适方法。此外，该研究表明，SMX 光解断裂过程中的同位素分馏程度取决于 pH 值。
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