Aurore L Schneiders, Johann Far, Lidia Belova, Allison Fry, Adrian Covaci, Erin S Baker, Edwin De Pauw, Gauthier Eppe
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引用次数: 0
Abstract
Per- and polyfluoroalkyl substances (PFAS) are contaminants of increasing concern, with over seven million compounds currently inventoried in the PubChem PFAS Tree. Recently, ion mobility spectrometry has been combined with liquid chromatography and high-resolution mass spectrometry (LC-IMS-HRMS) to assess PFAS. Interestingly, using negative electrospray ionization, perfluoroalkyl carboxylic acids (PFCAs) form homodimers ([2M-H]-), a phenomenon observed with trapped, traveling wave, and drift-tube IMS. In addition to the limited research on their effect on analytical performance, there is little information on the conformations these dimers can adopt. This study aimed to propose most probable conformations for PFCA dimers. Based on qualitative analysis of how collision cross section (CCS) values change with the mass-to-charge ratio (m/z) of PFCA ions, the PFCA dimers were hypothesized to likely adopt a V-shaped structure. To support this assumption, in silico geometry optimizations were performed to generate a set of conformers for each possible dimer. A CCS value was then calculated for each conformer using the trajectory method with Lennard-Jones and ion-quadrupole potentials. Among these conformers, at least one of the ten lowest-energy conformers identified for each dimer exhibited theoretical CCS values within a ±2% error margin compared to the experimental data, qualifying them as plausible structures for the dimers. Our findings revealed that the fluorinated alkyl chains in the dimers are close to each other due to a combination of C-F···O=C and C-F···F-C stabilizing interactions. These findings, together with supplementary investigations involving environmentally relevant cations, may offer valuable insights into the interactions and environmental behavior of PFAS.
期刊介绍:
The Journal of the American Society for Mass Spectrometry presents research papers covering all aspects of mass spectrometry, incorporating coverage of fields of scientific inquiry in which mass spectrometry can play a role.
Comprehensive in scope, the journal publishes papers on both fundamentals and applications of mass spectrometry. Fundamental subjects include instrumentation principles, design, and demonstration, structures and chemical properties of gas-phase ions, studies of thermodynamic properties, ion spectroscopy, chemical kinetics, mechanisms of ionization, theories of ion fragmentation, cluster ions, and potential energy surfaces. In addition to full papers, the journal offers Communications, Application Notes, and Accounts and Perspectives