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Evaluation of the three-phase equilibrium method for measuring temperature dependence of internally consistent partition coefficients (K(OW), K(OA), and K(AW)) for volatile methylsiloxanes and trimethylsilanol.

Xu S, Kropscott B - Environ. Toxicol. Chem. (2014)

Bottom Line: The measured partition coefficients at the different temperatures for any given compound, and the enthalpy and entropy changes for the corresponding partition processes, were all internally consistent, suggesting that the 3-phase equilibrium method is suitable for this type of measurement.Compared with common environmental contaminants reported in the literature, VMS have enthalpy and entropy relationships similar to those of alkanes for air/water partitioning and similar to those of polyfluorinated compounds for octanol/air partitioning, but more like those for benzoates and phenolic compounds for octanol/water partitioning.The temperature dependence of the partition coefficients of TMS is different from those of VMS and is more like that of alcohols, phenols, and sulfonamides.

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Affiliation: Health and Environmental Sciences, Dow Corning, Auburn, Michigan, USA.

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Comparison of the changes in enthalpies (ΔHOA) and entropies (ΔSOA) of octanol-to-air partitioning for volatile methylsiloxanes (VMS) and trimethylsilanol (TMS) with those for other environmental contaminants such as polyfluorinated compounds (PFCs) 42, polychlorinated naphthalenes (PCNs) 43, chlorinated benzenes (CBs), and polychlorinated biphenyls (PCBs) 13,44,45. The data for dodecamethylcyclohexasiloxane (D6) are from Xu and Kropscott 25. The dashed line represents the linear regression line for 6 VMS. L2 = hexamethyldisiloxane; L3 = octamethyltrisiloxane; L4 = decamethyltetrasiloxane; D4 = octamethylcyclotetrasiloxane; D5 = decamethylcyclopentasiloxane.
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fig04: Comparison of the changes in enthalpies (ΔHOA) and entropies (ΔSOA) of octanol-to-air partitioning for volatile methylsiloxanes (VMS) and trimethylsilanol (TMS) with those for other environmental contaminants such as polyfluorinated compounds (PFCs) 42, polychlorinated naphthalenes (PCNs) 43, chlorinated benzenes (CBs), and polychlorinated biphenyls (PCBs) 13,44,45. The data for dodecamethylcyclohexasiloxane (D6) are from Xu and Kropscott 25. The dashed line represents the linear regression line for 6 VMS. L2 = hexamethyldisiloxane; L3 = octamethyltrisiloxane; L4 = decamethyltetrasiloxane; D4 = octamethylcyclotetrasiloxane; D5 = decamethylcyclopentasiloxane.

Mentions: In addition, a good linear correlation (p << 0.01 for 2-tailed test) between ΔHOA and ΔSOA was observed for the 5 siloxanes (Figure 4) 8


Evaluation of the three-phase equilibrium method for measuring temperature dependence of internally consistent partition coefficients (K(OW), K(OA), and K(AW)) for volatile methylsiloxanes and trimethylsilanol.

Xu S, Kropscott B - Environ. Toxicol. Chem. (2014)

Comparison of the changes in enthalpies (ΔHOA) and entropies (ΔSOA) of octanol-to-air partitioning for volatile methylsiloxanes (VMS) and trimethylsilanol (TMS) with those for other environmental contaminants such as polyfluorinated compounds (PFCs) 42, polychlorinated naphthalenes (PCNs) 43, chlorinated benzenes (CBs), and polychlorinated biphenyls (PCBs) 13,44,45. The data for dodecamethylcyclohexasiloxane (D6) are from Xu and Kropscott 25. The dashed line represents the linear regression line for 6 VMS. L2 = hexamethyldisiloxane; L3 = octamethyltrisiloxane; L4 = decamethyltetrasiloxane; D4 = octamethylcyclotetrasiloxane; D5 = decamethylcyclopentasiloxane.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4257567&req=5

fig04: Comparison of the changes in enthalpies (ΔHOA) and entropies (ΔSOA) of octanol-to-air partitioning for volatile methylsiloxanes (VMS) and trimethylsilanol (TMS) with those for other environmental contaminants such as polyfluorinated compounds (PFCs) 42, polychlorinated naphthalenes (PCNs) 43, chlorinated benzenes (CBs), and polychlorinated biphenyls (PCBs) 13,44,45. The data for dodecamethylcyclohexasiloxane (D6) are from Xu and Kropscott 25. The dashed line represents the linear regression line for 6 VMS. L2 = hexamethyldisiloxane; L3 = octamethyltrisiloxane; L4 = decamethyltetrasiloxane; D4 = octamethylcyclotetrasiloxane; D5 = decamethylcyclopentasiloxane.
Mentions: In addition, a good linear correlation (p << 0.01 for 2-tailed test) between ΔHOA and ΔSOA was observed for the 5 siloxanes (Figure 4) 8

Bottom Line: The measured partition coefficients at the different temperatures for any given compound, and the enthalpy and entropy changes for the corresponding partition processes, were all internally consistent, suggesting that the 3-phase equilibrium method is suitable for this type of measurement.Compared with common environmental contaminants reported in the literature, VMS have enthalpy and entropy relationships similar to those of alkanes for air/water partitioning and similar to those of polyfluorinated compounds for octanol/air partitioning, but more like those for benzoates and phenolic compounds for octanol/water partitioning.The temperature dependence of the partition coefficients of TMS is different from those of VMS and is more like that of alcohols, phenols, and sulfonamides.

View Article: PubMed Central - PubMed

Affiliation: Health and Environmental Sciences, Dow Corning, Auburn, Michigan, USA.

Show MeSH
Related in: MedlinePlus