Perfluoroethercarboxylic acids (PFECAs) have recently emerged as replacements for toxic per- and polyfluorinated alkyl substances (PFAS) including perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Compared with other PFAS, many PFECAs including hexafluoropropylene oxide dimer acid (HFPO-DA, trade name GenX) exhibit poor sensitivity during analysis using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) and are therefore often difficult to quantify. This study examined changes in ESI probe position, mobile phase additive, and capillary voltage with the goal of enhancing PFECA sensitivity. In addition, the relative contributions of existing mechanistic theories for PFAS ionization during ESI are discussed. Results indicated that the LC-ESI-MS/MS sensitivity for 9 PFECAs can be improved significantly by altering the ESI probe position. At the optimal probe position, lowering the capillary voltage from 2.0 to 0.5 kV universally enhanced the LC-ESI-MS/MS sensitivity for PFAS analysis. For most analytes, the use of ammonium bicarbonate rather than ammonium acetate as a mobile phase additive also enhanced the analytical response. These effects have not been previously reported and suggest that many laboratories may be conducting analyses of PFECAs under suboptimal conditions. Using the strategies outlined in this study, PFECAs can be more easily incorporated into comprehensive methods for PFAS analysis. Here, we describe analytical parameters that enhance the sensitivity for some PFECAs by up to 36-fold while maintaining high sensitivity for legacy PFAS. This work not only highlights solutions to mitigate inadequate PFECA sensitivity but also provides insight into the mechanisms underlying PFAS ionization efficiency during LC-ESI-MS/MS.

中文翻译：

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使用LC-ESI-MS / MS增强全氟醚羧酸分析的灵敏度：探针位置，流动相添加剂和毛细管电压的影响。

全氟醚羧酸（PFECA）最近已经出现，作为有毒的全氟和多氟烷基物质（PFAS）的替代品，包括全氟辛酸（PFOA）和全氟辛烷磺酸（PFOS）。与其他PFAS相比，包括六氟环氧丙烷二聚酸（HFPO-DA，商品名GenX）在内的许多PFECA在使用液相色谱-电喷雾电离串联质谱（LC-ESI-MS / MS）分析期间显示出较差的灵敏度，因此通常很难量化。这项研究检查了ESI探针位置，流动相添加剂和毛细管电压的变化，目的是提高PFECA的灵敏度。此外，还讨论了现有机理理论在ESI期间对PFAS电离的相对贡献。结果表明，通过改变ESI探针位置，可以显着提高9种PFECA的LC-ESI-MS / MS灵敏度。在最佳探头位置，将毛细管电压从2.0 kV降低到0.5 kV，普遍提高了PFAS分析的LC-ESI-MS / MS灵敏度。对于大多数分析物，使用碳酸氢铵而不是乙酸铵作为流动相添加剂也可增强分析响应。这些影响以前尚未报道过，表明许多实验室可能在次优条件下进行了PFECA的分析。使用本研究中概述的策略，PFECA可以更轻松地整合到PFAS分析的综合方法中。在这里，我们描述了一些分析参数，这些参数可将某些PFECA的灵敏度提高多达36倍，同时保持对传统PFAS的高灵敏度。