MEASUREMENT OF LIPOPHILICITY INDEXES BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY - COMPARISON OF 2 STATIONARY PHASES AND VARIOUS ELUENTS

Twenty-eight benzene derivatives spanning a broad range of lipophilicities were used as model compounds to examine the optimum stationary phase and eluent conditions for the determination of lipophilic indices by reversed-phase high-performance liquid chromatography. This was assessed by linear regressions comparing published octanol-water partition coefficients with isocratic capacity factors and capacity factors extrapolated to 100% water in the eluent. Methanol-water eluents are always to be preferred to acetonitrile-water and tetrahydrofuran-water eluents. The octadecylsilane (ODS) phase yielded good correlations especially when a masking agent was added to the eluent, but this introduced an additional experimental variable. The octadecyl-polyvinyl copolymer (ODP) phase was just as satisfactory as the ODS phase without the need for a masking agent, and thus appears to be a valuable alternative.