Energy-dependent normal and unusually large inverse chlorine kinetic isotope effects of simple chlorohydrocarbons in collision-induced dissociation by gas chromatography-tandem mass spectrometry
| Autor: | Tang, Caiming, Tan, Jianhua, Zhang, Peilin, Fan, Yujuan, Yu, Zhiqiang, Peng, Xianzhi |
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| Rok vydání: | 2019 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | Kinetic isotope effects (KIEs) taking place in mass spectrometry (MS) can provide in-depth insights into the fragmental behaviors of compounds in MS. Yet the mechanisms of KIEs in collision-induced dissociation (CID) in tandem MS are unclear, and information about chlorine KIEs (Cl-KIEs) of organochlorines in MS is particularly scarce. This study investigated the Cl-KIEs of dichloromethane, trichloroethylene and tetrachloroethylene during CID using gas chromatography-electron ionization triple-quadrupole tandem MS. Cl-KIEs were measured with MS signal intensities, and their validity was confirmed in terms of chromatograms, crosstalk effects and background subtraction influences. All the organochlorines presented large inverse Cl-KIEs, showing the largest values of 0.492, 0.910 and 0.892 at the highest collision energy for dichloromethane, trichloroethylene and tetrachloroethylene, respectively. For dichloromethane, both intra-ion and inter-ion Cl-KIEs were studied, within the ranges of 0.492-1.020 and 0.614-1.026, respectively, showing both normal and inverse Cl-KIEs depending on collision energies. The observed Cl-KIEs generally declined with the increasing collision energies from 0-60 eV, but were inferred to be independent of MS signal intensities. The Cl-KIEs are dominated by critical energies at low internal energies, while controlled by rotational barriers (or looseness/tightness of transition states) at high internal energies. It is concluded that the Cl-KIEs may depend on critical energies, bond strengths, available internal energies, and transition state looseness/tightness. The findings of this study yield new insights into the fundamentals of Cl-KIEs of organochlorines during CID, and may be conducive to elucidating the mechanisms of KIEs in collision-induced and photo-induced reactions in the actual world. Comment: 37 pages, 6 figures |
| Databáze: | arXiv |
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