Structural Properties Governing Retention Mechanisms on RP-HPLC Stationary Phases Used for Lipophilicity Measurements

Abstract

In this study, the retention mechanisms on the Supelcosil LC-ABZ stationary phase were analyzed by linear solvation free-energy relationships (LSERs). In a first phase, a set of 60 compounds was selected by cluster analysis from a large set (253) compounds of known van der Waals volume (V_w), polarity/polarizability (π∗), H-bond donating acidity (α) and H-bond acceptor basicity (β). The capacity factors log k' at 40% methanol and the log k_w values were shown to be highly correlated with octanol/water partition coefficients (log P_oct) and to contain pratically the same structural information, as assessed by LSERs. Test sets of model compounds and dipeptides were used to validate the log k_w/log P and log k'/log P relations. For anions and zwitterions, specific interactions with the stationary phase occur which produce systematic deviations in the log k/log P relations.