Revisiting thin-layer chromatography as a lipophilicity determination tool. Part II — Is silica gel a reliable adsorbent for lipophilicity estimation?

Abstract

Lipophilicity is often estimated by thin-layer chromatography (TLC) as a fundamental property related to biological and pharmaceutical activity. In a recent study, we contributed some standardization to the subject by performing a comparative analysis of the different approaches in the field. This part presents an analogous study on silica, the use of which in normal-phase systems seems to be a new trend of recent times. We have compared several approaches of TLC lipophilicity determination: a single TLC run, Soczewinski-Wachtmeister equation coefficients, principal component analysis (PCA) of the retention matrix, and PARAFAC on a three-way array. All techniques were applied to 35 model solutes with simple molecules, using nine concentrations of six modifiers: acetone, dioxane, ethyl acetate, methylethylketone, propan-2-ol, and tetrahydrofuran. Comparative analysis points to several general recommendations. Ethyl acetate seems to give the best correlations with lipophilicity, and the correlations of sing...