RP-HPLC measurement and quantitative structureproperty relationship analysis of the n-octanolwater partitioning coefficients of selected metabolites of polybrominated diphenyl ethers

n-Octanolwater partitioning coefficient (log K_OW) values of selected hydroxylated and methoxylated polybrominated diphenyl ether metabolites were measured for the first time by reversed-phase high performance liquid chromatography (RP-HPLC) using a C18 stationary phase with a water/methanol mixture as a mobile phase. The retention parameters, log k_w (extrapolated retention indices) and k′ (gradient retention indices) were calibrated to log K_OW by a set of calibration standards. For the PBDE metabolites investigated, extrapolated retention indices from isocratic elution seem to be more reliable and their RP-HPLC-derived log K_OW values were found to range from 4.63 to 7.67. Some commonly available software, including ClogP, KowWin, AclogP, MlogP, AlogP, MilogP, and XlogP, was used to estimate the log K_OW values of the analytes. Significant correlations were obtained between the RP-HPLC-derived log K_OW and the software-computed log K_OW, with squared correlation coefficients (R²) ranging from 0.793 to 0.922, but the difference between them was also significant. Then a quantitative structureproperty relationship model based on topological descriptors was established and showed good reliability and predictive power for the estimation of RP-HPLC-derived log K_OW values of PBDE metabolites. It was applied to estimate the log K_OW values of some PBDE metabolites that are commercially available or have appeared in the literature. Lastly, factor analysis was carried out using the theoretical linear salvation/free-energy relationships, which indicated the average polarisability () and the most negative atomic partial Mulliken charge in the molecule (q^-) were the most important parameters affecting their partition between n-octanol and water, supporting the factorisation of log K_OW in bulk and electronic terms. © CSIRO 2008.