Determination of lipophilicity by reversed-phase high-performance liquid chromatography - Influence of 1-octanol in the mobile phase

Lipophilicity was evaluated using a novel R-P-HPLC stationary phase (Discovery-RP-Amide-Cl 6) with and without 1-octanol added to the mobile phase. A set of 46 drugs and flavonoids characterized by a broad structural diversity and a wide log P-oct range (-0.69 to 5.70) was selected for this study. This set consists of neutral solutes and solutes with acidic or ampholytic functionalities which were maintained neutral at pH 2.5 or 4. In our conditions, the addition of 1-octanol in the mobile phase proved a key factor to derive a lipophilicity index log k(w) highly correlated with log P-oct for all investigated solutes. 1-Octanol improved the correlation between log P-oct and log k(w) mainly by influencing the retention behavior of the solutes with log P-oct values below +3. This study brings additional evidence that under proper experimental conditions of stationary and mobile phases, RP-HPLC is a very useful method to obtain log P-oct values. (c) 2005 Elsevier B.V. All rights reserved.