McCord, J. and M. Strynar.
Environmental Science & Technology 53(9):4717-4727(2019)

Nontargeted screening was applied to samples obtained from the Cape Fear River of North Carolina, a fluorochemically impacted watershed. The continued presence of perfluorinated ether acids was confirmed by the detection of a total of 37 unique chemical formulas comprising 58 isomers. Structural determination was carried out by LC-MS/MS to determine isomeric structures where possible. Novel structures determined included perfluorinated ether acid species containing two acidic sites, polyfluorinated ether acids containing a single hydrogenation, and previously unreported perfluorinated ether acids. Compounds identified by an initial nontargeted screen were monitored over repeated sampling to track long-term reductions in PFAS content during emission source control. Hierarchical clustering of the time-course data was used to associate groups of chemicals based on their trends over time. Six clusters were identified and showed some similarity in chemical class; they are believed to represent the by-products of different fluorochemical production lines.See also a brief note on this study: https://phys.org/pdf474710802.pdf.