Modeling the Partitioning of Anionic Carboxylic and Perfluoroalkyl Carboxylic and Sulfonic Acids to Octanol and Membrane Lipid
Date
2023-07-13
Journal Title
Journal ISSN
Volume Title
Publisher
Environmental Toxicology and Chemistry
Abstract
Perfluoroalkyl carboxylic and sulfonic acids (PFCAs and PFSAs, respectively) have low acid dissociation constant values and are, therefore, deprotonated under most experimental and environmental conditions. Hence, the anionic species dominate their partitioning between water and organic phases, including octanol and phospholipid bilayers which are often used as model systems for environmental and biological matrices. However, data for solvent–water (SW) and membrane–water partition coefficients of the anion species are only available for a few per- and polyfluoroalkyl substances (PFAS). In the present study, an equation is derived using a Born-Haber cycle that relates the partition coefficients of the anions to those of the corresponding neutral species. It is shown via a thermodynamic analysis that for carboxylic acids (CAs), PFCAs, and PFSAs, the log of the solvent–water partition coefficient of the anion, log KSW(A−), is linearly related to the log of the solvent–water partition coefficient of the neutral acid, log KSW(HA), with a unity slope and a solvent-dependent but solute-independent intercept within a PFAS (or CA) family. This finding provides a method for estimating the partition coefficients of PFCAs and PFSAs anions using the partition coefficients of the neutral species, which can be reliably predicted using quantum chemical methods. In addition, we have found that the neutral octanol–water partition coefficient, log KOW, is linearly correlated to the neutral membrane–water partition coefficient, log KMW; therefore, log KOW, being a much easier property to estimate and/or measure, can be used to predict the neutral log KMW. Application of this approach to KOW and KMW for PFCAs and PFSAs demonstrates the utility of this methodology for evaluating reported experimental data and extending anion property data for chain lengths that are unavailable. Environ Toxicol Chem 2023;00:1–12. © 2023 SETAC
Description
This is the peer reviewed version of the following article: Torralba-Sanchez, T.L., Di Toro, D.M., Dmitrenko, O., Murillo-Gelvez, J. and Tratnyek, P.G. (2023), Modeling the Partitioning of Anionic Carboxylic and Perfluoroalkyl Carboxylic and Sulfonic Acids to Octanol and Membrane Lipid. Environ Toxicol Chem. https://doi.org/10.1002/etc.5716, which has been published in final form at https://doi.org/10.1002/etc.5716. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited. © 2023 SETAC. This article will be embargoed until 07/13/2024.
Keywords
QSAR, poly- and perfluoroalkyl substances, log KOW, speciation, environmental partitioning, Abraham pp-LFER, in silico calibration, pKa
Citation
Torralba-Sanchez, T.L., Di Toro, D.M., Dmitrenko, O., Murillo-Gelvez, J. and Tratnyek, P.G. (2023), Modeling the Partitioning of Anionic Carboxylic and Perfluoroalkyl Carboxylic and Sulfonic Acids to Octanol and Membrane Lipid. Environ Toxicol Chem. https://doi.org/10.1002/etc.5716