Comprehensive characterization of per- and polyfluoroalkyl substances (PFASs) is critical for environmental monitoring and remediation applications. PFASs are a large family of thousands of chemicals that have been extensively analyzed using nontargeted time-of-flight and Orbitrap mass spectrometry methods. 21T Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers the highest available mass resolving power for complex mixture analysis, and sub-ppm mass errors across a wide molecular weight range. To explore its application to suspect and nontargeted screening, we developed a 21T FT-ICR MS method to screen for PFASs in an aqueous film-forming foam (AFFF) sample (9,247 detected ions), using a dissolved organic matter (DOM) sample from a high-altitude stream (27,229 detected ions) as a negative control. The developed method included suspect screening for known PFASs (±0.2 ppm mass error), molecular formula assignment with a targeted database (C, H, Cl, F, N, O, P, S; ≤ 865 Da; ±0.2 ppm mass error), CF2 homologous series, 13C, 34S, and 37Cl isotopologues, and Kendrick-analogous mass difference networks. False positive PFAS identifications in the DOM sample suggested that a minimum length of 3 should be imposed when annotating CF2-homologous series, and conflicting formula assignments at sub-ppm errors indicated the importance of using isotopologues and homologous series during formula assignment. We putatively identified 199 known PFASs in the AFFF sample during suspect screening, and 124 more PFASs during additional nontargeted analysis. These results demonstrate that FT-ICR MS-based suspect and nontargeted screening methods can provide unique insights into complex PFAS compositions often encountered at AFFF-impacted sites.

Exploring the limits of PFAS analysis: Suspect and nontargeted screening with ultrahigh resolution 21T FT-ICR MS

ACS Spring 2022

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