Per- and polyfluoroalkyl substances (PFASs) are a class of aliphatic manufactured compounds comprising fluoro-chemicals with varied functional groups and stable carbon–fluorine bonds. They are defined as “forever chemicals” due to their persistent and bioaccumulative character. These substances have been detected in various environmental samples, including water, air, soil, and human blood, posing significant health hazards. High-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) is typically employed for the analysis of PFASs. Negative chemical ionization (NCI) is generally coupled to gas chromatography (GC) and offers high selectivity and sensitivity for compounds containing electronegative atoms, such as PFASs. The liquid electron ionization (LEI) interface is an efficient mechanism developed to robustly couple a liquid flow rate from an LC system to an EI or a CI source. This interface has been successfully utilized for pesticide determination in UHPLC-LEI-CI in negative ion mode (NCI). This work aims to evaluate different parameters involved in the ionization of PFASs analyzed in LC-LEI-NCI and subsequently develop a method for their detection in real samples. The parameters considered for this study include (i) a comparison of different CI reagent gases (methane, isobutane, and argon); (ii) the use of acetonitrile as both the chromatographic solvent and CI reagent gas; (iii) the presence of water and formic acid as chromatographic mobile phase components; and (iv) the mobile phase flow rate. The optimal combination of these parameters led to promising results. Tentative fragmentation pathways of PFASs in NCI mode are proposed based on the dissociative electron capture mechanism.

中文翻译：

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通过液体电子电离 LC-MS 接口探索全氟烷基和多氟烷基物质的负化学电离

全氟烷基物质和多氟烷基物质 (PFAS) 是一类脂肪族制造的化合物，由具有不同官能团和稳定碳氟键的含氟化合物组成。由于其持久性和生物累积性，它们被定义为“永久化学品”。这些物质已在各种环境样本中检测到，包括水、空气、土壤和人体血液，对健康构成重大危害。高效液相色谱法与电喷雾电离质谱联用 (HPLC-ESI-MS) 通常用于 PFAS 的分析。负化学电离 (NCI) 通常与气相色谱 (GC) 结合使用，可为含有负电原子的化合物（例如 PFAS）提供高选择性和灵敏度。液体电子电离 (LEI) 接口是一种有效的机制，旨在将液体流速从 LC 系统稳健地耦合到 EI 或 CI 源。该接口已成功用于 UHPLC-LEI-CI 负离子模式 (NCI) 中的农药测定。这项工作旨在评估 LC-LEI-NCI 中分析的 PFAS 电离所涉及的不同参数，并随后开发一种在实际样品中检测它们的方法。本研究考虑的参数包括 (i) 不同 CI 反应气体（甲烷、异丁烷和氩气）的比较； (ii) 使用乙腈作为色谱溶剂和 CI 反应气； (iii) 存在水和甲酸作为色谱流动相组分； (iv) 流动相流速。这些参数的最佳组合带来了有希望的结果。基于解离电子捕获机制，提出了 NCI 模式下 PFAS 的初步碎裂途径。