Selection of solvents for thin-layer chromatography by means of a simple ranking system based on dielectric constants.

1. A system devised for ranking t.l.c. solvent mixtures on the basis of their dielectric constants is useful in selecting mixtures for routine t.l.c. 2. For three basic compounds (tiquinamide, meptazinol and ciclazindol) and three acidic compounds (fentiazac, oxaprozin and 5, 6, 7, 8-tetrahydroquinoline-3-carboxylic acid), chromatographed on silica in the unionized state, a good correlation was found between RF and dielectric constant of the eluting solvent mixture.