Unveiling the hidden organofluorine burden: An integrated analytical framework to improve fluorine mass balance in...

Resolving the incomplete fluorine mass balance remains a central challenge in Per- and polyfluoroalkyl substances (PFAS) assessment, largely due to the underrepresentation of ultrashort-chain species and chemically unresolved compounds in complex water matrices. Here, we developed an integrated analytical framework that combining targeted analysis, ultrashort-chain PFAS quantification, extractable organic fluorine (EOF), and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS)-based screening. This approach enables robust characterization of high-matrix-load environmental samples and expands PFAS coverage beyond conventional targeted analysis. Across the investigated matrices, up to 57 fluorinated molecular formulas were tentatively identified in landfill leachate and 53 in municipal wastewater, while structural identification yields remained low (0.3-0.9%), indicating a substantial unresolved organofluorine fraction. Integrating targeted analysis of ultrashort-chain PFAS and non-target screening results significantly improved the explained fraction of EOF, reaching up to 85% in landfill leachate. Ultrashort-chain PFAS contributed 20-34% of EOF, while non-target screening suggested matrix-dependent enrichment of specific PFAS-related chemical domains in membrane concentrates. These findings demonstrate that combining ultrashort-chain PFAS analysis with high-resolution non-target screening provides a more constrained representation of the organofluorine pool and advances the resolution of fluorine mass balance in complex water systems.