http://precedings.nature.com/tags/Perfluorinated%20acids Recently posted documents tagged with 'Perfluorinated acids' Nature Publishing Group en Nature Precedings http://precedings.nature.com/images/header_logo.gif http://precedings.nature.com http://dx.doi.org/10.1038/npre.2009.3011.2 Organic carbon normalized soil and sediment-water partitioning coefficients (Koc) were estimated for all C1 through C8 perfluoroalkyl carboxylic (PFCA) and sulfonic (PFSA) acid congeners. The limited experimental Koc dataset for the straight chain C7 through C10 PFCAs and C8 and C10 PFSAs was correlated to SPARC and ALOGPS computationally estimated octanol-water partitioning / distribution constants and used to predict Koc values for both branched and linear C1 through C8 isomers. Branched and linear congeners in this homologue range are generally expected to have Koc values >1, leading to their accumulation in organic matter on sediments and soils, retardation during ground and pore water flow, and the preferential association with dissolved organic matter in aquatic systems. Both increasing perfluoroalkyl chain length and linearity increase Koc values with substantial intra- and inter-homologue variation and interhomologue mixing. Variability in Koc values among the PFCA and PFSA congeners will likely lead to an enrichment of more linear and longer chain isomers in organic matter fractions, resulting in aqueous phases fractionated towards shorter chain branched congeners. The expected magnitude of fractionation will require inclusion in source apportionment models and risk assessments. A comparison of representative established quantitative structure property relationships for estimating Koc values from octanol-water partitioning constants suggests that these equilibrium partitioning frameworks may be applicable towards modeling PFCA and PFSA environmental fate processes. http://dx.doi.org/10.1038/npre.2009.3011.2 Mon, 08 Jun 2009 08:44:24 UTC Congener specific organic carbon normalized soil and sediment-water partitioning coefficients for the C1 through C8 perfluoroalkyl carboxylic and sulfonic acids doi:10.1038/npre.2009.3011.2 2009-06-08 Sierra Rayne Nature Precedings 2009-06-08T08:44:24Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://dx.doi.org/10.1038/npre.2009.3282.2 New experimental data is available in the literature regarding the octanol-water distribution behavior of representative straight chain perfluoroalkyl carboxylate (PFCA) and sulfonate (PFSA) congeners. The current study provides the first investigation into the predictive ability of various software programs for estimating the corresponding octanol-water partitioning (log P) and distribution (log D) constants of PFCAs and PFSAs. Wide predictive variation was found within and between the various methods. Several programs were able to accurately estimate the log P/D fragmental contributions of a -CF2- group for PFCAs, as well as the associated Gibbs free energies for partitioning into octanol from water due to the hydrophobic character of the perfluoroalkyl chain (ΔhydrophobicGow). Only the SPARC log D method accurately predicted the electrostatic contributions of the carboxylate head group (ΔelectrostaticGow) towards octanol-water partitioning for PFCAs. Similar log D values and organic carbon normalized sediment-water partitioning coefficients (Koc) for PFCAs and PFSAs having equivalent perfluoroalkyl chain lengths suggests potentially equivalent ΔelectrostaticGow and ΔhydrophobicGow contributions towards lipophilic partitioning for these two contaminant classes at near neutral pH values, regardless of head group identity. In contrast, there are potentially different ΔelectrostaticGow and ΔhydrophobicGow contributions towards proteinophilic partitioning under biologically relevant conditions. http://dx.doi.org/10.1038/npre.2009.3282.2 Mon, 01 Jun 2009 10:51:14 UTC A comparative assessment of octanol-water partitioning and distribution constant estimation methods for perfluoroalkyl carboxylates and sulfonates doi:10.1038/npre.2009.3282.2 2009-06-01 Sierra Rayne Nature Precedings 2009-06-01T10:51:14Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/3282/version/1 New experimental data is available in the literature regarding the octanol-water distribution behavior of representative straight chain perfluoroalkyl carboxylate (PFCA) and sulfonate (PFSA) congeners. The current study provides the first investigation into the predictive ability of various software programs for estimating the corresponding octanol-water partitioning (log P) and distribution (log D) constants of PFCAs and PFSAs. Wide predictive variation was found within and between the various methods. Several programs were able to accurately estimate the log P/D fragmental contributions of a -CF2- group for PFCAs, as well as the associated Gibbs free energies for partitioning into octanol from water due to the hydrophobic character of the perfluoroalkyl chain (ΔhydrophobicGow). Only the SPARC log D method accurately predicted the electrostatic contributions of the carboxylate head group (ΔelectrostaticGow) towards octanol-water partitioning for PFCAs. Similar log D values and organic carbon normalized sediment-water partitioning coefficients (Koc) for PFCAs and PFSAs having equivalent perfluoroalkyl chain lengths suggests potentially equivalent ΔelectrostaticGow and ΔhydrophobicGow contributions towards lipophilic partitioning for these two contaminant classes, regardless of head group identity. In contrast, there are potentially different ΔelectrostaticGow and ΔhydrophobicGow contributions towards proteinophilic partitioning. http://precedings.nature.com/documents/3282/version/1 Tue, 26 May 2009 10:22:59 UTC A comparative assessment of octanol-water partitioning and distribution constant estimation methods for perfluoroalkyl carboxylates and sulfonates hdl:10101/npre.2009.3282.1 2009-05-26 Sierra Rayne Nature Precedings 2009-05-26T10:22:59Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/3256/version/1 SPARC, KOWWIN, and ALOGPS octanol-water partitioning (log Kow) 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 Kow and log D data and compared to available field and laboratory BCF data. Wide variability was observed between the methods for estimating log Kow 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 Kow based BCF equations. The SPARC and KOWWIN log Kow and log D values provided generally less accurate BCF estimates regardless of the BCF equation applied. However, the SPARC Kow values did provide BCF estimates for PFSA congeners with errors http://precedings.nature.com/documents/3256/version/1 Mon, 18 May 2009 14:05:29 UTC An assessment of organic solvent based equilibrium partitioning methods for predicting the bioconcentration behavior of perfluorinated sulfonic acids, carboxylic acids, and sulfonamides hdl:10101/npre.2009.3256.1 2009-05-18 Sierra Rayne Nature Precedings 2009-05-18T14:05:29Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/3011/version/1 Organic carbon normalized soil and sediment-water partitioning (Koc) coefficients were estimated for all C1 through C8 perfluorinated alkylsulfonic acid (PFSA) and alkylcarboxylic acids (PFCA) congeners. The limited experimental Koc dataset for the straight chain C7 through C10 PFCAs and C8 and C10 PFSAs was correlated to SPARC and ALOGPS computationally estimated octanol-water partitioning constants and used to predict Koc values for both branched and linear C1 through C8 isomers. All branched and linear congeners in this homologue range are expected to have Koc values>1, leading to their accumulation in organic matter on sediments and soils, retardation during ground and pore water flow, and the preferential association with dissolved organic matter in aquatic systems. Both increasing perfluoroalkyl chain length and linearity increase Koc values with substantial intra- and inter-homologue variation and interhomologue mixing. Variability in Koc values among the PFCA and PFSA congeners will likely lead to an enrichment of more linear and longer chain isomers in organic matter fractions, resulting in aqueous phases fractionated towards shorter chain branched congeners. The expected magnitude of fractionation will require inclusion in source apportionment models and risk assessments. A comparison of representative established quantitative structure property relationships for estimated Koc values from octanol-water partitioning constants suggests that equilibrium partitioning frameworks may be applicable towards modeling PFCA and PFSA environmental fate processes and warrants further study using other partitioning coefficients for which suitable experimental data is available. http://precedings.nature.com/documents/3011/version/1 Thu, 02 Apr 2009 12:43:31 UTC Congener specific organic carbon normalized soil and sediment-water partitioning coefficients for the C1 through C8 perfluorinated alkylsulfonic and alkylcarboxylic acids hdl:10101/npre.2009.3011.1 2009-04-02 Sierra Rayne Nature Precedings 2009-04-02T12:43:31Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://dx.doi.org/10.1038/npre.2008.1956.1 Perfluorinated acids (PFAs) are contaminants detected worldwide in a range of abiotic and biotic environmental matrices. The two major classes of PFAs include the perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), both of which are considered persistent and potentially bioaccumulative. Current research and regulatory efforts are focussed on the straight-chain members of each PFA class and homologue group, primarily because these congeners are the major components of technical mixtures and are also available as pure standards. However, the numerous potential branched congeners in each PFA class represent a poorly understood family of environmental contaminants whose environmental and toxicological properties may be more important than the more prevalent straight-chain members. To help broaden the current understanding of PFA environmental fate and toxicology, semi-empirical computational methods were used predict fundamental physico-chemical properties of all potential C4 to C8 PCFA and PFSA congeners. Established quantitative structure-activity models for other multi-class emerging and legacy contaminants were applied to estimate key parameters related to the toxicology, environmental partitioning, and abiotic and biotic degradation mechanisms for each PFA class. The findings provide guidance for developing new analytical methods for separating and identifying PFAs in environmental and technical mixtures, prioritizing efforts on synthesizing authentic standards, and focussing toxicological studies on the congeners most likely to be of concern. http://dx.doi.org/10.1038/npre.2008.1956.1 Tue, 10 Jun 2008 14:49:56 UTC Predicting the Congener-Specific Environmental Behaviour of Perfluorinated Acid Contaminants Using Semi-Empirical Computational Methods doi:10.1038/npre.2008.1956.1 2008-06-10 Sierra Rayne Nature Precedings 2008-06-10T14:49:56Z Poster Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/