| Title: | "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" |
| Address: | "Health and Environmental Sciences, Dow Corning, Auburn, Michigan, USA" |
| ISSN/ISBN: | 1552-8618 (Electronic) 0730-7268 (Print) 0730-7268 (Linking) |
| Abstract: | "Partitioning equilibria and their temperature dependence of chemicals between different environmental media are important in determining the fate, transport, and distribution of contaminants. Unfortunately, internally consistent air/water (K(AW)), 1-octanol/air (K(OA)), and 1-octanol/water (K(OW)) partition coefficients, as well as information on their temperature dependence, are scarce for organosilicon compounds because of the reactivity of these compounds in water and octanol and their extreme partition coefficients. A newly published 3-phase equilibrium method was evaluated for simultaneous determination of the temperature dependence of (K(OW), K(OA), and K(AW)) of 5 volatile methylsiloxanes (VMS) and trimethylsilanol (TMS) in a temperature range from 4 degrees C to 35 degrees C. 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" |
| Keywords: | "1-Octanol/chemistry Air Chromatography, High Pressure Liquid Entropy Kinetics Siloxanes/*chemistry Temperature Trimethylsilyl Compounds/*chemistry Volatile Organic Compounds/*chemistry Water/chemistry Enthalpy and entropy changes Enthalpy and entropy comp;" |
| Notes: | "MedlineXu, Shihe Kropscott, Bruce eng 2014/09/23 Environ Toxicol Chem. 2014 Dec; 33(12):2702-10. doi: 10.1002/etc.2754. Epub 2014 Oct 31" |
