Intermolecular Interactions, Solute Descriptors, and Partition Properties of Neutral Per- and Polyfluoroalkyl Substances (PFAS)

Self Cite

Partitioning from water to nonaqueous phases is an important process that controls the behavior of contaminants in the environment and biota. However, for ionic chemicals including many perfluoroalkyl and polyfluoroalkyl substances (PFAS), environmentally relevant partition coefficients cannot be predicted using the octanol/water partition coefficient, which is commonly used as a hydrophobicity indicator for neutral compounds. As an alternative, this study measured C 18 liquid chromatography retention times of 39 anionic PFAS and 20 nonfluorinated surfactants using isocratic methanol/water eluent systems. By measuring a series of PFAS with different perfluoroalkyl chain lengths, retention factors at 100% water (k 0 ) were successfully extrapolated even for long-chain PFAS. Molecular size was the most important factor determining the k 0 of PFAS and non-PFAS, suggesting that the cavity formation process is the key driver for retention. Log k 0 showed a high correlation with the log of partition coefficients from water to the phospholipid membrane, air/water interface, and soil organic carbon. The results indicate the potential of C 18 retention factors as predictive descriptors for anionic PFAS partition coefficients and the possibility of developing a more comprehensive multiparameter model for the partitioning of anionic substances in general.

Section: Resultscontrasting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Hydrophobic Sorption Properties of an Extended Series of Anionic Per- and Polyfluoroalkyl Substances Characterized by C₁₈ Chromatographic Retention Measurement

Endo,

Matsuzawa

2024

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“…To enhance the reliability of the PP-LFERs, nearly all descriptors in the calibration sets had been successfully applied in other partitioning systems. Three FTOHs (4:2 FTOH, 6:2 FTOH, and 8:2 FTOH), with descriptors recalibrated by Endo and co-workers, were also incorporated into the calibration sets for K i slip/w and K i slip/a , ,, which would be beneficial for predicting the K i slip/w and K i slip/a of the increasingly scrutinized per- and polyfluoroalkyl substances (PFASs) (detailed later). Compounds with descriptors accessible from the Abraham Absolv database, but seldom applied in other systems, were classified as validation compounds.…”

Section: Methodsmentioning

confidence: 99%

Polyparameter Linear Free Energy Relationships for Partitioning of Neutral Organic Compounds to Storage Lipids

Liu,

2024

Storage lipids are an important compartment in the bioaccumulation of neutral organic compounds. Reliable models for predicting storage lipid−water and storage lipid−air partition coefficients (K islip/w and K islip/a ), as well as their temperature dependence, are considered useful. Polyparameter linear free energy relationships (PP-LFERs) are accurate, general, and mechanistically clear models for predicting partitioning-related physicochemical quantities. About a decade ago, PP-LFERs were calibrated for K islip/w at the physiological temperature of 37 °C. However, to date, a comprehensive collection and sufficiently reliable PP-LFERs for K islip/w and K islip/a at the most common standard temperature of 25 °C are still lacking. In this study, experimentally based K islip/w and/or K islip/a values at 25 °C for 278 compounds were extensively collected or converted from the literature. Subsequently, PP-LFERs were calibrated for K islip/w and K islip/a at 25 °C, performing well over 10 orders of magnitude with root-mean-square errors of 0.17−0.21 log units for compounds with reliable descriptors. Furthermore, standard internal energy changes of transfer from water or air to storage lipids for 158 compounds were derived and used to calibrate PP-LFERs for estimating the temperature dependence of K islip/w or K islip/a . Additionally, using PP-LFERs, low-density polyethylene was confirmed to be a better storage lipid analogue than silicone and polyoxymethylene in the equilibrium passive sampling of nonpolar and H-bond acceptor polar compounds.

“…The cVMS share these unusual partitioning properties with certain polyfluoroalkyl substances (PFASs). For example, D5 has very similar partitioning properties as 1H,1H,2H,2H-perfluorododecyl acrylate (10:2-FTAC) and 1H,1H,2H,2H-perfluorododecyl methacrylate (10:2-FTMAC) . While we do not know whether PFASs would be considered viable cVMS replacements, they are potent greenhouse gases and known to degrade to bioaccumulative, toxic, and extremely persistent perfluoroalkyl acids .…”

Section: Recent Nominations Continue To Pay Insufficient Attention To...mentioning

confidence: 99%

“…For example, D5 has very similar partitioning properties as 1H,1H,2H,2H-perfluorododecyl acrylate (10:2-FTAC) and 1H,1H,2H,2H-perfluorododecyl methacrylate (10:2-FTMAC). 36 While we do not know whether PFASs would be considered viable cVMS replacements, they are potent greenhouse gases and known to degrade to bioaccumulative, toxic, and extremely persistent perfluoroalkyl acids. 37 There is every reason to believe that they would have a higher likelihood to lead to significant adverse human health and/or environmental effects as a result of LRET than cVMS.…”

Section: Insufficient Attention To the Possibility Of Regrettable Sub...mentioning

confidence: 99%

The Stockholm Convention at a Crossroads: Questionable Nominations and Inadequate Compliance Threaten Its Acceptance and Utility

Wania,

McLachlan

2024

Twenty years since coming into force, the Stockholm Convention has become a "living" global agreement that has allowed for the addition of substances that are likely, as a result of their long-range environmental transport (LRET), to lead to significant adverse effects. The recent listing of the phenolic benzotriazole UV-328 in Annex A and a draft nomination of three cyclic volatile methylsiloxanes (cVMS) for Annex B draw attention to the fact that many chemicals are subject to LRET and that this can lead to questionable nominations. The nomination of UV-328 and the draft nomination of cVMS also raise the spectre of regrettable substitutions. At the same time, atmospheric monitoring across the globe reveals that environmental releases of several unintentionally produced POPs listed in Annex C, such as hexachlorobenzene and hexachlorobutadiene, are continuing unabated, highlighting shortcomings in the enforcement of the minimum measures required under Article 5. There is also no evidence of efforts to substitute a chemical whose use has been known for three decades to unintentionally produce polychlorinated biphenyls. These developments need to be rectified to safeguard the long-term viability and acceptance of a global treaty of undeniable importance.