Measurement of Low Air–Water Partition Coefficients of Organic Acids

May 2, 2013 - Coefficients of Organic Acids by Evaporation from a Water Surface”. David A. Ellis*. ,†,‡. † ... Fax: 705 748 1625. Notes. The a...
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Reply to Comment on “Measurement of Low Air−Water Partition Coefficients of Organic Acids by Evaporation from a Water Surface” David A. Ellis*,†,‡ †

Department of Chemistry and ‡Centre for Environmental Modelling and Chemistry, Trent University, 1600 West Bank Drive, Peterborough, Ontario, K9J 7B8 Canada

I

thank you for your interest in our article1 describing the development of a new technique for the determination of the air−water partitioning coefficient (KAW) for perfluorooctanoic acid (PFOA). I agree, if PFOA indeed has a pKa of ∼0, this would have an impact, albeit minor, upon our reported KAW value measured at a pH of 0.6. The effect would be to reduce the reported KAW from a value of 1.02 × 10−3 to a value of ∼0.2 × 10−3. Currently, such a recommendation for change cannot be made due to the collective weight of the peer reviewed published experimental data2−5 that is in opposition to the experimental article which you cite.6 If any of the values published in the opposed articles were the true pKa value of PFOA, the original KAW would stand.

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AUTHOR INFORMATION

Corresponding Author

*E-mail [email protected]. Tel.: 705 748 1011 extn: 7898. Fax: 705 748 1625. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Li, H. X.; Ellis, D.; Mackay, D. Measurement of low air−water partition coefficients of organic acids by evaporation from a water surface. J. Chem. Eng. Data 2007, 52, 1580−1584. (2) Burns, D. C.; Ellis, D. A.; Li, H.; McMurdo, C. J.; Webster, E. Experimental pK(a) determination for perfluorooctanoic acid (PFOA) and the potential impact of pK(a) concentration dependence on laboratory-measured partitioning phenomena and environmental modeling. Environ. Sci. Technol. 2008, 42, 9283−9288. (3) Lopez-Fontan, J. L.; Sarmiento, F.; Schulz, P. C. The aggregation of sodium perfluorooctanoate in water. Colloid Polym. Sci. 2005, 283, 862−871. (4) Ylinen, M.; Kojo, A.; Hanhijarvi, H.; Peura, P. Disposition of perfluorooctanoic acid in the rat after single and subchronic administration. Bull. Environ. Contam. Toxicol. 1990, 44, 46−53. (5) Brace, N. O. Long chain alkanoic and alkenoic acids with perfluoroalkyl terminal segments. J. Org. Chem. 1962, 27, 4491−4498. (6) Cheng, J.; Psillakis, E.; Hoffman, M. R.; Collussi, A. J. Acid dissociation versus molecular association of perfluoroalkyl oxoacids: Environmental implications. J. Phys. Chem. A 2009, 113, 8152−8156.

Received: March 30, 2013 Accepted: April 10, 2013 Published: May 2, 2013 © 2013 American Chemical Society

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dx.doi.org/10.1021/je400303b | J. Chem. Eng. Data 2013, 58, 1884−1884