Estimating Octanol–Water Partition Coefficients of Novel Brominated Flame Retardants by Reversed‐Phase High‐Performance Liquid Chromatography and Computational Models

Abstract

AbstractLegacy brominated flame retardants, including polybrominated diphenyl ethers (PBDEs), have been classified as persistent organic pollutants and replaced with novel brominated flame retardants (NBFRs). The octanol–water partition coefficients (log KOW) of NBFRs have been computationally estimated, but the log KOW values provided by these methods can differ by 1 to 3 orders of magnitude. Given the importance of this parameter in fate and toxicity models, we indirectly measured the log KOW values of eight NBFRs by their capacity factor (k′) on a reversed‐phase high‐performance liquid chromatography (HPLC) C18 column by isocratic elution and compared these measured values with those estimated by nine computational models. Log KOW values were obtained for the NBFRs 1,2‐bis(2,4,6‐tribromophenoxy) ethane, pentabromobenzene, pentabromoethylbenzene, pentabromotoluene, 2‐ethylhexyl 2,3,4,5‐tetrabromobenzoate, allyl 2,4,6‐tribromophenylether, 2,3‐dibromopropyl‐2,4,6‐tribromophenyl ether, and bis(2‐ethylhexyl) tetrabromophthalate. A training set of phthalates, polychlorinated biphenyls, PBDEs, and halogenated benzenes were chosen to obtain the log k′–log KOW calibration for the NBFRs. The computational models KowWIN, XLogP3, EAS‐E Suite, COSMOtherm, DirectML, and Abraham polyparameter linear free energy relationships all predicted the log KOW values of the calibration compounds to within 1 order of magnitude without significant bias. The median of these models predicted log KOW values for the calibration compounds that were close to those known in the literature with root mean square error (RMSE) = 0.224 and for the NBFRs that were close to those measured by HPLC (RMSE = 0.334). Environ Toxicol Chem 2024;00:1–10. © 2024 SETAC