Thin-layer Chromatography of Plant Extracts. IV. Alkaloids.

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Abstract
Solvent mixtures previously used for developing thin-layer chromatograms of various groups of alkaloids have now been tested for other alkaloids and other plant material alkaloid fractions than those for which they were originally intended. Some were selected and arranged in order of increasing dielectric constant on a logarithmic scale for general use in the silica gel thin-layer chromatographic analysis of preparations containing alkaloids of corresponding polarity. Three new solvent mixtures have been developed: one acidic mixture of intermediate polarity consisting of chloroform, acetic acid, and methanol, 60:5:35, one alkaline mixture of intermediate polarity consisting of butanol, chloroform, and ammonia, 50:10:4, and one acidic mixture of high polarity consisting of ethanol, formic acid, water, and formamide, 50:10:10:30. The Rr values for an alkaloid usually differ considerably if alkaline solvents and if acid solvents of the same dielectric constant are used for developing the chromatogram.