Lipophilicity measurement by Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC): A comparison of two stationary phases based on retention mechanisms

Abstract

The mechanisms of retention of two recent stationary phases of interest in lipophilicity measurements, namely of the silica-based Discovery-RP-Amide-C16 phase and the polymer-based ODP-50-4B phase, were assessed and compared. A set of 41 model solutes and drugs with well-defined solvatochromic parameters were selected to allow a broad distribution of property spaces. The chromatographic results showed that, under the conditions of study, the lipophilicity index log kw obtained with the former stationary phase was more closely related to experimental log Poct values than was log kw obtained with the ODP-50-4B phase. Linear solvation/ free-energy relationship (LSER) analyses showed that the retention mechanisms of the two stationary phases are different, retention on the Discovery-RP-Amide-C16 phase and partitioning in octan-1-ol/H2O being controlled by the same balance of intermolecular forces (Van der Waals volume Vw, H-bond acceptor basicity β, and dipolarity/polarizability π*).