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 (ϕCH3OH) 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 logk′ 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 POW values are related to extrapolated log k0 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 POW values with reasonable accuracy.