Atmospheric Oxidation of Polyfluorinated Amides: Historical Source of Perfluorinated Carboxylic Acids to the Environment

Polyfluorinated amides (PFAMs) are a class of fluorinated compounds which were produced as unintentional byproducts in the electrochemical fluorination process used for polyfluorinated sulfonamide synthesis in 1947-2002 To investigate the historical potential of PFAMs as an atmospheric perfluorinated acid (PP CA) source we studied N-ethylperfluorobutyramide (EtFBA) as a surrogate for longer chained PFAMs. Smog chamber relative rate techniques were used to measure bimolecular rate coefficients for reactions of EtFBA with chlorine atoms and hydroxyl radicals. It was found k(CI) = (2.08 +/- 0.15) X 10(-11) cm(3) molecule(-1) s(-1) and k(OH) = (2.65 +/- 0.50) X 10(-12) cm(3) molecule(-1) s(-1) and the atmospheric lifetime of EtFBA with respect to reaction with OH was estimated to be approximately 4.4 days. Offline sampling with both GC-MS and LC-MS/MS techniques was used to determine the products and hence a plausible pathway of atmospheric oxidation of EtFBA. Three primary oxidation products were observed by GC-MS, the N-deallcylation product C3F7C(O)NH2 and two carbonyl products, probably C3F7C(O)N(H)C(O)CH3 and C3F7C(O)N(H)CH2CHO. These primary products react further to give perfluorocarboxylic acids (PFCAs) as detected by LC-MS/MS, suggesting that eight carbon PFAMs were a historical source of PFCAs to remote regions, including the Canadian Arctic.