Graduate School of Global Environmental Studies, Kyoto University, Yoshida, Sakyo-Ku, Kyoto, Japan.
Graduate School of Global Environmental Studies, Kyoto University, Yoshida, Sakyo-Ku, Kyoto, Japan.
J Chromatogr A. 2021 Feb 8;1638:461899. doi: 10.1016/j.chroma.2021.461899. Epub 2021 Jan 13.
Per- and polyfluoroalkyl substances (PFASs) have environmentally persistent, and the various types of PFASs have been detected in water environments. Many previous studies have performed data-dependent acquisition (DDA) of mass spectra from an environmental sample by high-resolution mass spectrometry to identify PFAS suspects individually. In comparison, the data-independent acquisition (DIA) of comprehensive mass spectra of the sample is a technology which enables to know the occurrences of suspects and non-targets simultaneously. However, it is difficult to associate the fragment ions of targeted precursor ions by retention time only, because of the existence of co-eluting ions derived from environmental samples. Since the separation of ions is not enough with only the conventional DIA method, here, we attempted to support it using ion mobility mass spectrometry (IMS) to distinguish the relevant ions from co-eluting ions by drift time. Firstly, suspect screening of PFASs with eternal database resulted in determining 32-96 PFAS suspects in firefighting foam impacted groundwater samples (n = 8) by suspect screening. Among all the pairs of respective precursor ions and fragment ions of the PFAS suspects, 5%-19% (4-9 PFASs) of them were associated without considering the drift time of IMS, while 37%-49% (15-43 PFASs) of them were associated with considering the drift time. The consideration of the drift time increased the association ratios in all samples. In a sample, most precursor ions could be associated with their fragment ions (41 of 43 PFASs) because at least one probable fragment ion was observed among three of maximum intensity fragment ions. Thus, the method improved the identification by excluding the unrelated co-eluting ions by IMS. Moreover, the method can acquire a certain reliable MS/MS spectra of suspects in environmental samples in one analysis. It is not essential to conduct instrumental analyses again for samples stored for a long time even when the data sets and/or methodologies of data analyses are modified (e.g., the original database, screening list, or statistical filtering/data cleaning approach). It will be particularly useful for studies that must analyze a large number of environmental samples.
全氟和多氟烷基物质（PFAS）具有环境持久性，各种类型的 PFAS 已在水环境中被检测到。许多先前的研究通过高分辨率质谱对环境样品进行基于数据依赖性采集（DDA），以单独识别 PFAS 可疑物。相比之下，对样品的综合质谱进行非依赖性采集（DIA）是一种能够同时了解可疑物和非目标物出现情况的技术。然而，仅通过保留时间很难将靶向前体离子的碎片离子关联起来，因为环境样品中的共洗脱离子的存在。由于仅使用常规 DIA 方法，离子的分离还不够，因此，我们尝试使用离子淌度质谱（IMS）通过漂移时间来区分相关离子和共洗脱离子，以支持该方法。首先，通过永恒数据库对 PFAS 进行可疑物筛选，在消防泡沫影响的地下水样本（n = 8）中确定了 32-96 种 PFAS 可疑物。在所有 PFAS 可疑物的相应前体离子和碎片离子对中，在不考虑 IMS 漂移时间的情况下，有 5%-19%（4-9 种 PFAS）可以关联，而在考虑 IMS 漂移时间的情况下，有 37%-49%（15-43 种 PFAS）可以关联。考虑漂移时间会增加所有样本中的关联比例。在一个样本中，由于在三个最大强度碎片离子中至少观察到一个可能的碎片离子，因此大多数前体离子可以与其碎片离子关联（43 种 PFAS 中的 41 种）。因此，该方法通过 IMS 排除不相关的共洗脱离子来提高鉴定的准确性。此外，该方法可以在一次分析中获取环境样品中可疑物的可靠 MS/MS 谱。即使数据集中的可疑物的数量很少，也无需再进行仪器分析，即使修改了数据分析的数据集合和/或方法（例如，原始数据库、筛选列表或统计过滤/数据清理方法）。对于必须分析大量环境样本的研究，这将特别有用。
