ABSTRACT Rationale Many perfluoroalkyl and polyfluoroalkyl sulfonic/sulfinic acids and their derivatives are classified as perfluoroalkyl and polyfluoroalkyl substances (PFASs). The use of mass spectrometry techniques to analyze these compounds has attracted considerable research attention. Methods In this article, we employed high‐resolution electrospray ionization tandem mass spectrometry (HR‐ESI‐MS/MS) and all‐ion fragmentation (AIF) in negative ion mode to investigate gas‐phase F‐atom migration reactions of various perfluoroalkyl and polyfluoroalkyl sulfonic/sulfinic anions, particularly those yielding FSO 3 − or FSO 2 − . Results HR‐ESI‐MS/MS of CF 3 SO 3 − yielded an unexpected product ion FSO 3 − , representing a distinct pathway of gas‐phase F‐atom migration from C‐atom to S‐atom accompanied by the loss of CF 2 . Similarly, HR‐ESI‐MS/MS of CF 3 SO 2 − produced a dominant product ion FSO 2 − also via CF 2 elimination. Complementary ESI‐MS/MS and AIF experiments on these anions confirmed that FSO 2 − and/or FSO 3 − are their characteristic fragmentation ions. Conclusion Theoretical calculations of gas‐phase reactions CF 3 SO 3 − → FSO 3 − + CF 2 and CF 3 SO 2 − → FSO 2 − + CF 2 were performed to investigate the possible F‐atom migration mechanisms. These results show that FSO 3 − at m/z 99 and/or FSO 2 − at m/z 83 could serve as diagnostic ions for structural elucidation of perfluoroalkyl and polyfluoroalkyl sulfonic/sulfinic acids and their derivatives in non‐target PFASs analyses by using mass spectrometry.
Liu et al. (2026) studied this question.