气相色谱柱上卤代有机污染物的氯、溴同位素分馏
Chlorine and Bromine Isotope Fractionation of Halogenated Organic Pollutants on Gas Chromatography Columns
摘要：
化合物特异性氯/溴同位素分析（CSIA-Cl/Br）已成为研究卤代有机污染物（HOPs）降解途径和确定污染源的有效手段。CSIA-Cl/Br通常通过气相色谱-质谱（GC-MS）进行，这可能会受到GC柱上HOP的氯和溴同位素分馏的负面影响。本研究采用GC-双聚焦扇形磁区高分辨质谱（GC-DFS-HRMS）技术，系统研究了31种有机氯和4种有机溴的Cl/Br同位素分馏特征。探讨了HOPs的柱上氯/溴同位素分馏行为，呈现出不同的同位素分馏模式和程度。29个HOPs表现出反同位素分馏，只有多氯联苯-138（PCB-138）和PCB-153表现出正常同位素分馏。其余4个HOPs没有观察到同位素分馏，PCB-101、1，2，3，7，8-五氯二苯并呋喃、PCB-180和2，3，7，8-四氯二苯并呋喃。不同HOPs的同位素分馏程度从低于可观察阈值（0.50%）到7.31%（PCB-18）不等。用Craig-Gordon模型和修正的双膜模型对柱上氯/溴同位素分馏机理进行了初步解释。反同位素效应和正同位素效应可能共同贡献于总同位素效应，从而决定同位素分馏的方向和程度。根据研究结果，对CSIA-Cl/Br研究提出了改进建议，以提高CSIA-Cl/Br研究结果的精密度和准确度。本研究结果将为CSIA-Cl/Br气相色谱-质谱联用技术的发展提供参考，并有助于开展CSIA-Cl/Br气相色谱-质谱联用技术研究啤酒花的环境行为和污染源。
英文摘要：
Compound-specific chlorine/bromine isotope analysis (CSIA-Cl/Br) has become a useful approach for degradation pathway investigation and source appointment of halogenated organic pollutants (HOPs). CSIA-Cl/Br is usually conducted by gas chromatography-mass spectrometry (GC-MS), which could be negatively impacted by chlorine and bromine isotope fractionation of HOPs on GC columns. In this study, 31 organochlorines and 4 organobromines were systematically investigated in terms of Cl/Br isotope fractionation on GC columns using GC-double focus magnetic-sector high resolution MS (GC-DFS-HRMS). On-column chlorine/bromine isotope fractionation behaviors of the HOPs were explored, presenting various isotope fractionation modes and extents. Twenty-nine HOPs exhibited inverse isotope fractionation, and only polychlorinated biphenyl-138 (PCB-138) and PCB-153 presented normal isotope fractionation. And no observable isotope fractionation was found for the rest four HOPs, i.e., PCB-101, 1,2,3,7,8-pentachlorodibenzofuran, PCB-180 and 2,3,7,8-tetrachlorodibenzofuran. The isotope fractionation extents of different HOPs varied from below the observable threshold (0.50%) to 7.31% (PCB-18). The mechanisms of the on-column chlorine/bromine isotope fractionation were tentatively interpreted with the Craig-Gordon model and a modified two-film model. Inverse isotope effects and normal isotope effects might contribute to the total isotope effects together and thus determine the isotope fractionation directions and extents. Proposals derived from the main results of this study for CSIA-Cl/Br research were provided for improving the precision and accuracy of CSIA-Cl/Br results. The findings of this study will shed light on the development of CSIA-Cl/Br methods using GC-MS techniques, and help to implement the research using CSIA-Cl/Br to investigate the environmental behaviors and pollution sources of HOPs.
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