Determination of lipophilicity by means of reversed-phase thin-layer chromatography. I. Basic aspects and relationship between slope and intercept of TLC equations

The main aspects of the authors' chromatographic work are reviewed. The determination of lipophilicity by means of TLC techniques is mainly based on the linear relationship between RM values and organic solvent concentrations in the mobile phase, as described by the TLC equation. The very good correlation between experimental and extrapolated RM values supports the validity of the extrapolation technique. Another interesting aspect is that the nature of the organic solvent does not affect the measurement of lipophilicity. However, the main purpose of this paper was to re-examine all the TLC equations in order to assess whether the relationship between intercepts and slopes is a basic feature of the chromatographic determination of lipophilicity. The analysis of more than 700 TLC equations showed that the above relationship holds only when dealing with series of strictly congeneric compounds. The structural meaning of chromatographic congenerity is discussed. © 1994.