Estimation of octanol/water partition coefficients for organic pollutants using reverse-phase HPLC

Octanol/water partition coefficients (K_ow's) of organic solutes are estimated with reasonable accuracy (standard deviation ± 0.25 log K_ow units) by elution from a C-18 column with 75:25 (v/v) MeOH-H₂O, based on results with 37 test compounds. Changes in solute activity coefficients from water to 75% MeOH account for the slope of the log K_ow-log k' plot, where k' is the HPLC capacity factor. The method is used to estimate K_ow's for 25 additional organic compounds, and some disparities between the results and those calculated using group additivity-constitutive factors are noted.