Analysis of the Relative Abundances of Perfluorooctane Sulfonate Isomers in Biological Samples

The presence and distribution of per- and polyfluoroalkyl substances (PFAS) in eggs of four avian species, including—Canada Geese, Mallard, Ring-billed Gull, and Double-crested Cormorants were analyzed. Results showed that in all species, perfluorooctane sulfonate (PFOS) was the dominant form, with the highest concentrations observed in the egg yolk from Double-crested Cormorant (511 to 2566 ppb). PFAS analysis was performed using liquid chromatography (LC) with ion mobility spectroscopy (IMS) and high-resolution mass spectrometry (HRMS), which allowed separation of the linear (L-PFOS) from the non-linear (branched) PFOS isomers. The measured PFAS levels in the bird eggs suggests stereoselectivity of PFOS bioaccumulation. The isomeric distribution pattern of non-linear PFOS in yolks were significantly different between cormorant, gulls, and mallard, and also differed from the PFOS reference standard, indicating that bioaccumulation of PFAS is stereoselective. Other biological samples, such as fish, human blood and breast milk were analyzed by LC-IMS-HRMS to determine if a general trend on the bioaccumulation pattern can be observed with regards to PFOS because the stereochemistry of PFAS will affect protein binding. The challenges and relevance of separating isomers of PFAS, and how stereochemistry may impact toxicity and biodegradation will be discussed.