Resolving unknown isomers of emerging per- and polyfluoroalkyl substances (PFASs) in environmental samples using COSMO-RS-derived retention factor and mass fragmentation patterns.

Chromatographic retention factors (k) and mass spectral fragmentation patterns of per- and polyfluoroalkyl substances (PFASs) were determined using the optimized parameters in liquid chromatography with tandem high-resolution mass spectrometry (LC-HRMS) analysis. Characteristic fragment ions obtained at various collision energies (MS ² fragmentation) were used to determine the structures of newly discovered (emerging) PFASs detected from industrial effluent and surface water samples. Moreover, COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) derived octanol-water partition coefficients (K _ow ), along with mean isotropic polarizabilities calculated from Density Functional Theory (DFT), of known PFASs were plotted against their experimental k values (k _exp ) to obtain a multivariable regression model that can be used to predict k values of unknown PFASs. The k values of different structural isomers of unknown PFASs were calculated and compared to k _exp. The predicted k value for the isomer that matches the MS ² fragmentation observed was found to be within 4.2 % of k _exp . This study demonstrates the applicability of an approach that combines the observed MS ² fragmentation patterns and k values, together with computationally-derived log K _ow and polarizabilities, in assigning the structures of unknown PFASs at environmentally relevant conditions when no reference standards are available.
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