TLC Determination of Hydrophilicity Parameter of Some Pyridinium Aldoximes

Abstract

The chemical structures of certain drug candidates give only a minimum of lipophilicity. Investigation of their elution on reversed‐phase materials was difficult, even when the water content of the mobile phase was changed. The dominative role of lipophilicity, either in the drugs' penetration or in the receptorial drug binding, is considered to be valid solely in the same chemical group of the various drugs.

In the cases of extremely lipophobic (i.e., hydrophilic) compounds, both the determination or calculation of lipophilicity was difficult or impossible. This is the reason that a novel index, the TLC hydrophilicity parameter, should be introduced as a substitute for lipophilicity.

Hydrophilicity can be preferrably determined using a planar stationary phase and an aqueous‐organic mobile phase. Numerical data of hydrophilicity on silica stationary phase can be calculated using R_M values, similar to the lipophilicity indices.

Keywords:

• Pyridinium aldoximes
• Hydrophylicity
• TLC
• Silica
• R_M values

Acknowledgments

This project was sponsored by the research grant of the Hungarian National Research Fund (OTKA T049492). Advice from Dr. L. S. Ettre are highly appreciated.