Per- and polyfluoroalkyl substances (PFAS) are difficult to analyze in environmental media due challenges such as extraction recovery and lack of analytical standards. The total oxidizable precursor (TOP) assay and suspect screening analysis coupled with semiquantitative (SQ) concentration estimates are two approaches to assess total PFAS in environmental media, but studies are needed to optimize workstreams for total PFAS analysis. This study applied two soil extraction methods, TOP assay, and SQ analysis to three aqueous film-forming foams (AFFFs) and three AFFF-impacted soils. In soils, the total PFAS estimated with results from an extraction method utilizing sequential acidic and basic solvents led to a 35% increase in precursors during TOP assay relative to results from a basic solvent only extraction in one of three soils tested, but concentrations did not increase significantly in remaining soils. Furthermore, sample-specific dilution schemes were required to overcome matrix effects caused by the acidic extraction step that influenced estimates of total PFAS by SQ analysis. The results highlight that there is not an advantage to routine application of an acid extraction step in PFAS-impacted soils. In three AFFFs, suspect screening of post-TOP samples identified eight classes of PFAS present after oxidation. Concentrations of three classes increased, suggesting they are new TOP end points. Concentrations of the remaining five classes either remained constant after TOP or exhibited slight decreases. As a result, combined TOP and SQ workstreams may yield the most representative assessment of total PFAS composition and concentration. The eight classes of PFAS present after TOP did not degrade in harsh conditions. Some are structurally similar to PFCAs and PFSAs and are known to occur in the environment, suggesting a similar degree of persistence and a need for more routine monitoring.

中文翻译：

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一种测定总全氟烷基物质和多氟烷基物质 (PFAS) 的综合方法

由于萃取回收和缺乏分析标准等挑战，全氟烷基物质和多氟烷基物质 (PFAS) 难以在环境介质中进行分析。总可氧化前体 (TOP) 测定和可疑筛选分析以及半定量 (SQ) 浓度估计是评估环境介质中总 PFAS 的两种方法，但需要研究来优化总 PFAS 分析的工作流程。本研究对三种水成膜泡沫 (AFFF) 和三种受 AFFF 影响的土壤应用了两种土壤提取方法、TOP 分析和 SQ 分析。在土壤中，与在三种测试土壤之一中仅使用碱性溶剂提取的结果相比，使用连续酸性和碱性溶剂的提取方法的结果估计的总 PFAS 导致 TOP 测定期间前体增加 35%，但剩余土壤中的浓度没有显着增加。此外，需要特定样品的稀释方案来克服由酸性提取步骤引起的基质效应，这种效应会影响 SQ 分析对总 PFAS 的估计。结果表明，在受 PFAS 影响的土壤中常规应用酸提取步骤没有优势。在三个 AFFF 中，对 TOP 后样品的可疑筛选确定了氧化后存在的八类 PFAS。三个类别的浓度增加，表明它们是新的 TOP 端点。其余五个类别的浓度在 TOP 之后保持不变或略有下降。因此，结合 TOP 和 SQ 工作流程可能会产生对总 PFAS 组成和浓度的最具代表性的评估。TOP 之后出现的八类 PFAS 在恶劣条件下没有降解。有些在结构上与 PFCA 和 PFSA 相似，并且已知会在环境中发生，这表明存在相似程度的持久性，需要进行更多的常规监测。