Shedding Light on PFAS Dark Matter Using a Novel GC-HRMS Approach

With thousands of documented perfluoroalkyl and polyfluoroalkyl substances (PFASs), novel methods are needed to comprehensively characterize these fluorinated compounds in the environment, biota, and humans. Despite being the most common approach, liquid chromatography high-resolution mass spectrometry (LC-HRMS) only covers a fraction of PFASs. To address this gap, we developed a nontargeted gas chromatography high-resolution mass spectrometry (GC-HRMS) workflow to extend coverage of the PFAS chemical space, developing and incorporating the most extensive GC HRMS PFAS libraries to date covering over 1,900 electron ionization (EI) and positive chemical ionization (PCI) predicted and experimental spectra. Five environmental and biological matrices were assessed: aqueous film forming foam (AFFF), industrial outfall, municipal leachate, residential floor dust, and human blood. A novel compound was identified (2-(perfluorohexyl)ethanethiol) in multiple AFFF formulations. A rarely monitored PFAS was additionally detected (N-methyl-N-(2-hydroxyethyl)perfluorooctanesulfonamide, N-MeFOSE) in human blood, industrial outfall, municipal leachate, and residential floor dust at high frequency and abundance. A comparison to LC-HRMS approaches for leachate and blood showed no overlap between annotated PFASs. The nontargeted workflow presented here provides essential tools to expand PFAS monitoring capabilities and identify previously undetected compounds that may pose significant health and environmental risks.