Identification and Characterization of Per- and Polyfluoroalkyl Substances Isomers in Bird Eggs by Liquid...

Per- and polyfluoroalkyl substances (PFASs) are widely used, with significant environmental and health impacts. PFASs often exist as isomers with distinct physicochemical properties that influence their environmental fate and toxicity. This study advances PFAS analysis through isomeric resolution of 41 linear and 39 branched congeners by liquid chromatography-ion mobility-high-resolution mass spectrometry (LC-IM-HRMS), reporting the largest collision cross-section (CCS) data set for PFAS structural isomers to date, including the first reported drift-tube ion mobility (DTIM)-derived DTCCSN2 values for PFNA and PFNS isomers. The workflow was successfully applied to 41 great and blue tit egg samples collected near a contaminated industrial site in Belgium, where 20 linear and 34 branched PFAS isomer features were detected. Correlation analysis between the number of isomers detected for each PFAS in bird eggs revealed distinct co-occurrence patterns among branched PFAS isomers, with PFBS and PFDoDA showing unique behavior compared with other PFAS classes. A significant difference in PFOS isomer profiles was identified between the two species, which may be related to differences in foraging behavior and species-specific accumulation. The results demonstrate that LC-IM-HRMS is a useful tool for confidence-enhanced PFAS isomer identification in complex biological samples despite the limited availability of single-branched isomer standards and highlight the value of isomer-resolved analysis for environmental biomonitoring and exposure characterization.