Narrowing Down the Identity of Extractable Organofluorine in Killer Whale Blubber

Unlike many other persistent organic pollutants that accumulate in lipid rich tissues, most known per and polyfluoroalkyl substances (PFAS) accumulate in protein rich tissues such as liver and blood. The recent discovery of elevated concentrations of unidentified extractable organofluorine (EOF) in killer whale blubber shows this rule might not be applicable to all PFAS. The aim of this study was to narrow down the possible nature of the unknown lipophilic organofluorine.

Analysis of a second Greenlandic killer whale confirmed the original findings from Schultes et al. (2020), which showed >90% of unexplained EOF and very similar target PFAS profiles. Thereafter, extracts were subjected to the total oxidizable precursor assay, which revealed low to negligible perfluoroalkyl carboxylic acid formation, indicating the organofluorine substance(s) were not perfluoroalkyl acids-precursors. Solvent extraction using hexane improved extraction efficiency compared to acetonitrile, suggesting a neutral/non-polar organofluorine substance. This observation was further supported by a lack of sorption to strong anion and cation exchange resins. Overall, these experiments point towards a neutral/non-polar non-PFAA forming organofluorine substance.

Efforts to characterize the purified extracts by ¹⁹F NMR were unsuccessful, possibly due to the relatively high detection limits of this technique. A negative result might also indicate that the organofluorine is comprised of several neutral substances and not just one or a few substances in high concentration. Finally, a suspect screen for fluorinated liquid crystal monomers (LCMs) was carried out by gas chromatography-high resolution mass spectrometry (GC-HRMS). While these substances display physical-chemical properties which align with those of our unidentified organofluorine, no fluorinated LCMs were detected from this analysis. Future work will apply a broader GC-HRMS-based non-targeted screening in an effort to further narrow down the identity of this unknown organofluorine.