Suspect Screening for PFAS in Groundwater with an Accessible LC–MS Workflow

Groundwater in North America is contaminated with per- and polyfluoroalkyl substances (PFAS) at more than 9500 locations. A major source of this contamination is aqueous film-forming foam (AFFF), widely used for fire suppression at military facilities and airfields. Many of the thousands of PFAS remain poorly characterized and are not amenable to targeted quantitative analytical methods, which allow them to remain undetected. Suspect screening, an analytical strategy that searches for potential or likely compounds from a predefined list without requiring analytical reference standards, combined with liquid chromatography-high resolution tandem mass spectrometry (LC-HRMS/MS), has emerged as an alternative or complementary approach to classical targeted analysis. Herein, an accessible suspect screening workflow was developed using data-dependent acquisitions and the NIST suspect list of 4712 PFAS, processed with TraceFinder software, followed by FreeStyle MS2 spectral management. Eleven PFAS were identified in AFFF-impacted groundwaters, including six compounds previously undetected by targeted experiments: 1H-perfluoropentane, 1H-perfluoroheptane, perfluorobutylsulfonamide (FBSA), perfluorohexanesulfonamide (FHxSA), perfluoropropanesulfonamide (FPrSA), and perfluoropropanesulfonic acid (PFPrS). Direct sample injection imposed sensitivity limitations, likely preventing the detection of additional PFAS present at lower concentrations. Nevertheless, the simplicity and reduced software investment requirements of this workflow make it a promising approach for broad adoption by the scientific community.