High-performance thin-layer chromatography on amino-bonded silica gel: application to barbiturates and steroids

The retention of some barbiturates and steroids on amino-bonded silica gel pre-coated plates was examined by employing high-performance thin-layer chromatography and compared with that on silica gel pre-coated plates, with respect to the pure organic solvent used as the eluent. Aqueous and non-aqueous binary mixtures were also tested as eluents. The retentions on the two types of plates were generally different. For the pure organic solvents, the relative solvent strength on NH2-modified plates did not follow an order resembling that reported for other polar supports, such as alumina. The subdivision of the solvents in several classes, postulated for silica support, may explain some differences in chromatographic behaviour with respect to the eluent and to the compounds examined.