Adsorbent Layers and Solvents for TLC

The thin-layer chromatographic separation of alkaloids can be performed on silica gel, alumina, cellulose powder or kieselguhr. Silica gel is the most active stationary phase good separations are achieved even when several milligrams substance are applied. Alumina is less 

Giacopellb [70b] has used Avicel, a microcrystalline cellulose (see p. 34) for TLC of alkaloids. The hB/-values of 48 alkaloids have been measured on these layers, using 5 solvents. The layers are prepared as a rule on flat [268], or, more rarely, grooved glass plates (Fig. 16 c) of varying sizes. 

Pabis [161b] has recommended coated sheets (see p. 69) for fractionating some alkaloids. Information about the possibilities of preparative TLC is on pp. 97—102. 

During the brief period of its application the TLC of alkaloids has become such a general method that many authors consider it no longer necessary to quote in their publication the adsorbent, whether loose or adhering, the solvent, chamber saturation etc. 

Waldi et al. [257] have described a so-called systematic analysis of alkaloids for rapid identification purposes, using TLC on silica gel. It has served as the basis for a great deal of later work. Apart from these authors, Teichert et al. [241, 242], Kamp et al. [99], Paris [160, 161], Pfeifer et al. [267] and Schwarz et al. [87, 201b, 201c, 212] have all investigated systematically the TLC of alkaloids. The chromatographic behaviour of the best known alkaloids could thus be established 

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