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An assessment of organic solvent based equilibrium partitioning methods for predicting the bioconcentration behavior of perfluorinated sulfonic acids, carboxylic acids, and sulfonamides

Sierra Rayne¹ and Kaya Forest²

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1. Ecologica Research
2. Okanagan College

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Manuscript

Date:

Received 16 May 2009 02:26 UTC; Posted 18 May 2009

Subjects:

Chemistry, Earth & Environment

Tags:

• Perfluorinated acids
• perfluoroalkyl carboxylates
• perfluoroalkyl sulfonates
• equilibrium partitioning
• bioconcentration factor

Abstract:

SPARC, KOWWIN, and ALOGPS octanol-water partitioning (log K_ow) and distribution (log D) constants were calculated for all C₁ through C₈ and the straight chain C₉ through C₁₅ perfluoroalkyl sulfonic acids (PFSAs) and carboxylic acids (PFCAs). Application of five established models for estimating bioconcentration factors (BCFs) were applied to the PFSA and PFCA log K_ow and log D data and compared to available field and laboratory BCF data. Wide variability was observed between the methods for estimating log K_ow and log D values, ranging up to several log units for particular congeners, and which was further compounded by additional variability introduced by the different BCF equations applied. With the exception of n-perfluorooctanecarboxylic acid (n-PFOA), whose experimental BCF was poorly modeled by all approaches, the experimental BCF values of the other PFSA and PFCA congeners were reasonably approximated by the ALOGPS log P values in combination with any of the five log K_ow based BCF equations. The SPARC and KOWWIN log K_ow and log D values provided generally less accurate BCF estimates regardless of the BCF equation applied. However, the SPARC K_ow values did provide BCF estimates for PFSA congeners with errors <0.3 log units using any of the five BCF equations. Model lipophilic and proteinophilic solvent based distribution constant calculations for the PFSA and PFCA congeners with experimental BCFs exhibited similar relationships with their corresponding BCF values. For longer chain PFCA and PFSA congeners, increasing hydrophobicity of the perfluoroalkyl chain appears to be driving corresponding increases in BCF values. Perfluorooalkyl sulfonamides are expected to display similar chain length and branching pattern influences on BCFs, but no experimental data are currently available upon which to validate the estimated values which range widely between the various approaches by up to 10 log units. The amidic proton acidity on primary and secondary perfluoroalkyl sulfonamides will play a significant role in the partitioning of these compounds with both abiotic and biotic organic matter, and will need to be taken into account when assessing their environmental and biological fate.

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This document is licensed to the public under the Creative Commons Attribution 3.0 License

How to cite this document:

Rayne, Sierra and Forest, Kaya. An assessment of organic solvent based equilibrium partitioning methods for predicting the bioconcentration behavior of perfluorinated sulfonic acids, carboxylic acids, and sulfonamides. Available from Nature Precedings <http://hdl.handle.net/10101/npre.2009.3256.1> (2009)

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