Identification of Unsaturated and 2H Polyfluorocarboxylate Homologous Series and Their Detection in Environmental Samples and as Polymer Degradation Products.

A pair of homologous series of polyfluorinated degradation products have been identified, both having structures similar to perfluorocarboxylic acids but (i) having a H substitution for F on the α carbon for 2H polyfluorocarboxylic acids (2HPFCAs) and (ii) bearing a double bond between the α-β carbons for the unsaturated PFCAs (2uPFCAs). Obtaining an authentic sample containing 2uPFOA and 2HPFOA, we optimized a mass-spectrometric multiple-reaction-monitoring (MS/MS) technique and then identified uPFCA and HPFCA homologous series in sludge-applied agricultural soils and fodder grasses for cattle grazing. Analysis of samples from a degradation experiment of commercial fluorotelomer-based polymers (FTPs), the dominant product of the fluorotelomer industry, confirmed that commercial FTPs are a potential source of uPFCAs and HPFCAs to the environment. We further confirmed the identity of the uPFCAs by imposing high-energy ionization to decarboxylate the uPFCAs then focused on the fluorinated chains in the first MS quadrupole. We also employed this high-energy ionization to decarboxylate and analyze PFCAs by MS/MS (for the first time, to our knowledge). In exploratory efforts, we report the possible detection of unsaturated perfluorooctanesulfonate in environmental samples, having a conceptual double-bond structure analogous to uPFOA. Using microcosms spiked with fluorotelomer compounds, we found 2uPFOA and 2HPFOA to be generated from unsaturated 8:2 fluorotelomer acid (8:2 FTUCA) and propose β- and α-oxidation mechanisms for generation of these compounds from 8:2 FTUCA. In light of these experimental results, we also reexamined the proposed biodegradation pathways of 8:2 fluorotelomer alcohol.