It has been reported that isotope fractionation can occur on gas chromatography (GC), yet little is known about concurrent dual-elements isotope fractionations on GC. Revelation of concurrent two-dimensional carbon and chlorine/bromine isotope fractionations of halogenated organic compounds (HOCs) on GC may be of important significance for compound-specific isotope analysis (CSIA). This study presents an in-depth investigation of the two-dimensional C and Cl/Br isotope fractionations of HOCs on GC using GC-double focus magnetic-sector high resolution mass spectrometry (GC-DFS-HRMS). The two-dimensional C and Cl/Br isotope fractionations of four organochlorines and four bromobenzenes on GC were simultaneously measured by GC-DFS-HRMS. The isotope fractionations were evaluated with isotope ratios, relative variations of isotope ratios (△hE) and isotope fractionation extents (ΛhE). All the HOCs exhibited significant inverse C and Cl/Br isotope fractionations, with Λ13C of 38.14‰-307.56‰, Λ37Cl of 59.60‰-146.85‰, and Λ81Br of 25.89‰-142.10‰. The isotope fractionations were significant in both ends of chromatographic peaks, while the isotope ratios in center retention-time segments were the closest to comprehensive isotope ratios in the whole peaks. Significant correlations between C isotope fractionation and Cl/Br isotope fractionation were observed, indicating that the isotope fractionations might have strong relationships and/or be dominated by similar factors. Relevant mechanisms for the two-dimensional C and Cl/Br isotope fractionations were tentatively proposed on basis of a modified two-film model and the theories related to zero point energy. The results of this study gains new insights into concurrent two-dimensional isotope fractionation behaviors of HOCs during physical processes, and are conducive to CSIA studies involving C, Cl and Br for obtaining high-quality data, particularly to dual-elements CSIA of C and Cl/Br.

中文翻译：

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气相色谱法同时观察卤代有机化合物的同时二维碳和氯/溴同位素分馏

据报道，可以在气相色谱 (GC) 上进行同位素分馏，但对 GC 上同时进行的双元素同位素分馏知之甚少。揭示 GC 上卤化有机化合物 (HOC) 的并发二维碳和氯/溴同位素分馏可能对化合物特定同位素分析 (CSIA) 具有重要意义。本研究使用 GC-双焦点磁扇区高分辨率质谱 (GC-DFS-HRMS) 对 GC 上 HOC 的二维 C 和 Cl/Br 同位素分馏进行了深入研究。GC-DFS-HRMS 同时测量 GC 上四种有机氯和四种溴苯的二维 C 和 Cl/Br 同位素分馏。同位素分馏用同位素比率评估，同位素比值（△hE）和同位素分馏程度（ΛhE）的相对变化。所有 HOC 均表现出显着的 C 和 Cl/Br 逆同位素分馏，其中 Λ13C 为 38.14‰-307.56‰，Λ37Cl 为 59.60‰-146.85‰，Λ81Br 为 25.89‰-142.10‰。色谱峰两端的同位素分馏显着，而中心保留时间段的同位素比值最接近全峰的综合同位素比值。观察到 C 同位素分馏和 Cl/Br 同位素分馏之间的显着相关性，表明同位素分馏可能具有很强的相关性和/或受相似因素的支配。基于改进的双膜模型和零点能量相关理论，初步提出了二维C和Cl/Br同位素分馏的相关机制。本研究结果对物理过程中 HOCs 的并行二维同位素分馏行为有了新的认识，有利于 C、Cl 和 Br 的 CSIA 研究以获得高质量的数据，特别是 C 和 Br 的双元素 CSIA氯/溴。