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

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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 (Vw), 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 kw values were shown to be highly correlated with octanol/water partition coefficients (log Poct) 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 kw/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.