PFAS Analysis with Ultrahigh Resolution 21T FT-ICR MS: Suspect and Nontargeted Screening with Unrivaled Mass Resolving Power and Accuracy

Per-
and polyfluoroalkyl substances (PFASs) are a large family
of thousands of chemicals, many of which have been identified using
nontargeted time-of-flight and Orbitrap mass spectrometry methods.
Comprehensive characterization of complex PFAS mixtures is critical
to assess their environmental transport, transformation, exposure,
and uptake. Because 21 tesla (T) Fourier-transform ion cyclotron resonance
mass spectrometry (FT-ICR MS) offers the highest available mass resolving
power and sub-ppm mass errors across a wide molecular weight range,
we developed a nontargeted 21 T FT-ICR MS method to screen for PFASs
in an aqueous film-forming foam (AFFF) using suspect screening, a
targeted formula database (C, H, Cl, F, N, O, P, S; ≤865 Da),
isotopologues, and Kendrick-analogous mass difference networks (KAMDNs).
False-positive PFAS identifications in a natural organic matter (NOM)
sample, which served as the negative control, suggested that a minimum
length of 3 should be imposed when annotating CF2-homologous
series with positive mass defects. We putatively identified 163 known
PFASs during suspect screening, as well as 134 novel PFASs during
nontargeted screening, including a suspected polyethoxylated perfluoroalkane
sulfonamide series. This study shows that 21 T FT-ICR MS analysis
can provide unique insights into complex PFAS composition and expand
our understanding of PFAS chemistries in impacted matrices.