Octanol:water partition coefficients (P): measurement, estimation, and interpretation, particularly for chemicals with P greater than 10(5).

Methods for measurement and estimation of octanol:water partition coefficients are discussed with particular reference to high values (log P greater than 5). A novel experimental method for P measurement is described and preliminary results presented. The use of high performance liquid chromatography capacity factors for estimating P values has been investigated; better correlations between the two parameters have been found if HPLC results at different methanol:water liquid phases are extrapolated to pure water, but even this procedure does not always give reliable P values. The interpretation of high log P values in terms of fish bioconcentration is discussed and the correlations of molecular connectivity and molecular weight with fish bioconcentration are presented.