Direct measurement of octanol–water partition coefficients of some environmentally relevant brominated diphenyl ether congeners

Abstract

Octanol–water partition coefficients ( K OW) of nine environmentally relevant brominated diphenyl ether (BDE) congeners present in two technical mixtures were directly measured using a slow-stir technique. Log K OW values of tri- to heptabrominated BDE congeners ranged from 5.74 to 8.27, and were related to bromine content by the equation logK OW =0.621( #Br)+4.12 (R 2=0.970) . The directly determined K OW values were generally lower than those calculated using fragment constant methods, particularly at higher levels of bromine substitution. The quasi-experimental approach of using fragment constants to modify a “backbone” compound of known K OW was much more successful than using the fragment constants to “build” the entire molecule. The tri- and tetrabrominated congeners are in the range of optimum bioaccumulation potential.