Estimating subcooled liquid vapor pressures and octanol-air partition coefficients of polybrominated diphenyl ethers and their temperature dependence.

Both subcooled liquid vapor pressure ( P L ) and octanol–air partition coefficient ( K OA ) are widely used as descriptors to predict gas-particle partitioning behavior of semi-volatile organic compounds (SVOCs), such as polybrominated diphenyl ethers (PBDEs). These two descriptors are functions of temperature, which are expressed as the Clausius-Clapeyron equations with the coefficients A L and B L for P L (log P L = A L + B L / T ) and A O and B O for K OA (log K OA = A O + B O / T ), where T is temperature in K. In this study, a simple equation to relate log K OA and log P L (log K OA = −log P L + 6.46) was derived, which also links the coefficients of A L & B L and A O & B O . Regression analysis of published data of internal energy Δ U OA for 22 PBDE congeners with their mole mass was made, leading a regression equation to calculate the internal energy for all 209 PBDE congeners. Three datasets of log K OA at 25 °C for all 209 PBDE congeners were evaluated; the one with the best match with experimentally measurements was selected. Using the datasets and equations described above, we calculated the values of Clausius-Clapeyron coefficients A O & B O and A L & B L for all 209 PBDE congeners at the following steps. First, B O was computed using the values of Δ U OA . Next, we calculated the values of A O using the values of B O and the values of log K OA at 25 °C. Finally, the values of the parameter A L and B L were determined for all 209 PBDE congeners. Results are in consistent with data available in the literature and the accuracy of the data were also evaluated. With these Clausius-Clapeyron coefficients, the values of P L and K OA at any environmentally relevant temperature can be calculated for all 209 PBDE congeners, and thus provides a quick reference for environmental monitoring and modeling of PBDEs. [ABSTRACT FROM AUTHOR]