Tang Caiming, Tan Jianhua, Xiong Songsong, Liu Jun, Fan Yujuan, Peng Xianzhi
State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Guangzhou Quality Supervision and Testing Institute, Guangzhou, 510110, China.
J Chromatogr A. 2017 Sep 8;1514:103-109. doi: 10.1016/j.chroma.2017.07.058. Epub 2017 Jul 25.
Compound-specific chlorine/bromine isotope analysis (CSIA-Cl/Br) has become a powerful approach to investigate degradation pathways and apportion sources of halogenated organic pollutants (HOPs) in the environment. CSIA-Cl/Br is usually conducted by gas chromatography-mass spectrometry (GC-MS), which could be negatively impacted by isotope fractionation on GC columns. In this study, on-column Cl/Br isotope fractionation of 31 organochlorines and 4 organobromines was explored using GC-double focus magnetic-sector high resolution MS (GC-DFS-HRMS). Twenty-nine HOPs exhibited inverse Cl/Br isotope fractionation for which the heavier isotopologues eluted faster than the lighter ones on GC columns, and two polychlorinated biphenyls (PCB-138 and PCB-153) showed normal isotope fractionation, whereas the rest four HOPs did not show observable isotope fractionation. The isotope fractionation extents varied from -13.0‰ to 73.1‰. Mechanisms of the on-column Cl/Br isotope fractionation were tentatively elucidated with a modified two-film model. The results demonstrate that integrating peak area as complete as possible for separable chromatographic peaks and integrating the middle retention-time segments for the inseparable peaks are helpful to improve precision and accuracy of the CSIA-Cl/Br data. The findings of this study will shed light on development of CSIA-Cl/Br methods with respect to improving precision and accuracy.
化合物特异性氯/溴同位素分析（CSIA-Cl/Br）已成为研究环境中卤代有机污染物（HOPs）降解途径和来源分配的有力方法。CSIA-Cl/Br通常通过气相色谱-质谱联用（GC-MS）进行，而这可能会受到GC柱上同位素分馏的负面影响。在本研究中，使用气相色谱-双聚焦磁扇形高分辨率质谱仪（GC-DFS-HRMS）探究了31种有机氯和4种有机溴的柱上Cl/Br同位素分馏情况。29种HOPs表现出反向Cl/Br同位素分馏，即较重的同位素异构体在GC柱上的洗脱速度比较轻的快，两种多氯联苯（PCB-138和PCB-153）表现出正常的同位素分馏，而其余4种HOPs未表现出可观察到的同位素分馏。同位素分馏程度在-13.0‰至73.1‰之间。采用改进的双膜模型初步阐明了柱上Cl/Br同位素分馏的机制。结果表明，对于可分离的色谱峰尽可能完整地积分峰面积，对于不可分离的峰积分中间保留时间段，有助于提高CSIA-Cl/Br数据的精密度和准确度。本研究结果将为提高CSIA-Cl/Br方法的精密度和准确度提供启示。
