Torralba-Sanchez Tifany L, Di Toro Dominic M, Dmitrenko Olga, Murillo-Gelvez Jimmy, Tratnyek Paul G
Mutch Associates, Hawthorne, New York, USA.
Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware, USA.
Environ Toxicol Chem. 2023 Nov;42(11):2317-2328. doi: 10.1002/etc.5716. Epub 2023 Aug 17.
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 K (A ), is linearly related to the log of the solvent-water partition coefficient of the neutral acid, log K (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 K , is linearly correlated to the neutral membrane-water partition coefficient, log K ; therefore, log K , being a much easier property to estimate and/or measure, can be used to predict the neutral log K . Application of this approach to K and K 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;42:2317-2328. © 2023 SETAC.
全氟烷基羧酸和磺酸（分别为PFCA和PFSA）具有较低的酸解离常数，因此在大多数实验和环境条件下会发生去质子化。因此，阴离子形态在它们于水相和有机相之间的分配中占主导地位，这些有机相包括辛醇和磷脂双层，它们常被用作环境和生物基质的模型体系。然而，关于阴离子形态的溶剂 - 水（SW）和膜 - 水分配系数的数据仅适用于少数全氟和多氟烷基物质（PFAS）。在本研究中，通过玻恩 - 哈伯循环推导了一个方程，该方程将阴离子的分配系数与相应中性物质的分配系数联系起来。通过热力学分析表明，对于羧酸（CA）、PFCA和PFSA，阴离子的溶剂 - 水分配系数的对数log K (A )与中性酸的溶剂 - 水分配系数的对数log K (HA)呈线性关系，斜率为1，且在一个PFAS（或CA）家族中，截距取决于溶剂但与溶质无关。这一发现提供了一种利用中性物质的分配系数来估算PFCA和PFSA阴离子分配系数的方法，而中性物质的分配系数可以使用量子化学方法可靠地预测。此外，我们发现中性辛醇 - 水分配系数log K 与中性膜 - 水分配系数log K 呈线性相关；因此，log K 作为一个更容易估算和/或测量的性质，可用于预测中性log K 。将该方法应用于PFCA和PFSA的K 和K ，证明了该方法在评估已报道的实验数据以及扩展链长不可用的阴离子性质数据方面的实用性。《环境毒理学与化学》2023年；42:2317 - 2328。© 2023 SETAC。
