Fluorinated Polymeric Ionic Liquids Enable Selective Preconcentration of Volatile Perfluoroalkyl Substances

Neutral volatile and semi-volatile per- and polyfluoroalkyl substances (PFAS) remain an under-quantified source of human and environmental PFAS exposure, largely due to their trace-level occurrence and the complexity of matrices. These analytical challenges underscore the need for selective extraction approaches capable of minimizing matrix interferences. In this work, a new generation of solid phase microextraction (SPME) devices, incorporating a polymeric ionic liquid (PIL) sorbent featuring linear and branched perfluoroalkyl moieties was developed, and their capability for the selective extraction and preconcentration of neutral volatile PFAS was systematically evaluated. The inclusion of fluorinated structural elements within the sorbents increased their affinity toward fluorinated analytes, consistent with enhanced fluorophilic interactions. In addition, the sorption mechanism of the developed fluorinated PIL-based SPME fibers was investigated. While most PIL fibers exhibited absorption-type partitioning, a PIL fiber featuring a fluorinated monomer and a cross-linker displayed adsorption behavior, as evidenced by the concentration-dependent competitive adsorption of lower-affinity analytes by higher-affinity species. Energy-dispersive X-ray spectroscopy (EDX) maps of the fluorinated PIL fiber revealed a heterogeneous fluorine distribution, indicating tightly clustered perfluorinated domains. The fluorinated sorbents were compared to a commercial divinylbenzene (DVB)/carbon-wide range (C-WR)/PDMS SPME fiber using non-targeted extraction of volatile organic compounds (VOCs) from the headspace (HS) of paint samples to assess relative selectivity. The PIL fibers exhibited markedly enhanced selectivity toward fluorinated compounds relative to non-fluorinated VOCs, achieving PFAS-positive hit rates of 4-17%, compared to only 1% observed with a commercial, non-fluorinated sorbent.