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Acid dissociation versus molecular association of perfluoroalkyl oxoacids: environmental implications

Psyllaki Eleftheria, Cheng Jie, Colussi Arthur, Gabriella, 1957-, Hoffmann M. R.

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URIhttp://purl.tuc.gr/dl/dias/10879274-4BE4-42A0-B396-51B61788C939-
Identifierhttps://doi.org/10.1021/jp9051352-
Identifierhttps://pubs.acs.org/doi/abs/10.1021/jp9051352-
Languageen-
Extent4 pagesen
TitleAcid dissociation versus molecular association of perfluoroalkyl oxoacids: environmental implicationsen
CreatorPsyllaki Eleftheriaen
CreatorΨυλλακη Ελευθεριαel
CreatorCheng Jieen
CreatorColussi Arthur, Gabriella, 1957-en
CreatorHoffmann M. R.en
PublisherACSen
PublisherAmerican Chemical Societyen
Content SummaryPerfluorooctanoate (PFO) and perfluorooctanesulfonate (PFOS) surfactant anions, once released, may rapidly reach remote regions. This phenomenon is puzzling because the water-bound anions of strong F-alkyl acids should be largely transported by slow oceanic currents. Herein, we investigate whether these hydrophobic F-alkyl oxoanions would behave anomalously under environmental conditions, as suggested elsewhere. Negative electrospray ionization mass spectra of micromolar aqueous PFO or PFOS solutions from pH 1.0 to 6.0 show (1) m/z ) 499 (PFOS) signals that are independent of pH and (2) m/z ) 413 (PFO) and 369 (PFO - CO2) signals, plus m/z ) 213 (C F CO -) and 169 (C F -) signals at higher collision energies, and, below pH ∼ 372 37 4, m/z ) 827 signals from a remarkably stable (PFO)2H- cluster that increase with decreasing pH. Since the sum of the m/z ) 369, 413, and 827 signal intensities is independent of pH, that is, effectively encompasses all major species, we infer that pKa(PFOSA) < 1.0 and pKa(PFOA) < 1.0. We also derive K2 e 4 × 107 M-2 for the clustering equilibrium 2PFO + H+ h (PFO)2H. Thus, although (PFO)2H is held together by an exceptionally strong homonuclear covalent hydrogen bond, neither PFOS nor PFO will associate or protonate significantly at environmentally relevant subnanomolar concentrations above pH ∼ 1.en
Type of ItemPeer-Reviewed Journal Publicationen
Type of ItemΔημοσίευση σε Περιοδικό με Κριτέςel
Licensehttp://creativecommons.org/licenses/by/4.0/en
Date of Item2015-09-24-
Date of Publication2009-
SubjectPerfluoroalkyl oxoacidsen
Bibliographic CitationJ .Cheng, E. Psillakis, M. R. Hoffmann and A. J. Colussi , "Acid dissociation versus molecular association of perfluoroalkyl oxoacids: environmental implications", J. Phys. Chem. A, vol.113, no. 29, pp.8152–8156, Jul. 2009. doi: 10.1021/jp9051352en

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