Determination of n-octanol/water partition coefficient by reversed-phase high performance liquid chromatography with cholesteryl-bonded phase

Retention behaviors of neutral and weak acidic compounds were studied systematically on a novel cholesteryl-bonded phase column. The relationships between retention factor (k) with volume fraction of organic modifier (phi) were established for each compound with methanol and acetonitrile as organic modifiers. The values of log k(w) corresponding to 100% water as mobile phase were obtained by extrapolating procedure. Models of the logarithm of n-octanol/water partition coefficient (log K-ow) versus log k(phi) (log k(w)) with different mobile phases were established. The values of log k(w) of some compounds were predicted with validated models. The results indicated that methanol as organic modifier was more suitable for determination of log K-ow with cholester columns than acetonitrile. For neutral or acidic compounds in neutral forms, the values of log k(w) could be predicted with log k(phi) from mobile phases with any volume fraction of methanol; for acidic compounds ionized in the mobile phases, the values of log k(w) were predicted with the extrapolated log k(w) values. Comparison of log K-ow-log k(phi) models established on cholester columns in this work with those established on C-18 and C-8 columns from the references indicated that it exists special interactions between compounds and the cholesteryl-bonded phase, which deserves further study.