Relationship between log Pow, shake-flask values and capacity factors derived from reversed-phase high-performance liquid chromatography for n-alkylbenzenes and some oecd reference substances

Abstract

The capacity factors ( k′) of eight n-alkylbenzenes and eleven reference substances used in the OECD Chemicals Testing Programme were determined using reversed-phase high-performance liquid chromatography (RP-18) at different compositions of the mobile phase (methanol—water). All substances except urea show a good linear relationship ( r ⩾ 0.995) between the 1n ḱ values and the volume fraction (ϕ CH 3OH ) of the organic modifier in the range 0.6–0.95. Correlation of n-octanol water partition coefficients (shake-flask values) given in the literature and from the OECD/EEC laboratory comparison tests with the experimental log k′ values results in a good linear relationship for the n-alkylbenzenes ( r, = 0.998) and a slightly poorer relationship for the OECD reference substances ( r = 0.967–0.986). If the log P OW values are related to extrapolated log k 0 values with pure water as the ecluent, the regression lines of both the homologues and the reference substances are nearly identical and can reciprocally be used to predict their log P OW values with reasonable accuracy.