A thin-layer chromatographic test for the identification of some drugs: its application to steroids, tetracyclines, penicillins and cephalosporins
The identity test described is based on the thin-layer chromatographic separation of the complex mixtures of substances formed by thermal degradation of small amounts of many organic substances applied as spots to thin-layer plates. Subsequent development of the plate, and the application of spray reagents when necessary, yields characteristic patterns that are suitable for comparison under 254- and 366-nm ultraviolet light with authentic specimens that have been similarly treated. The test has been found to give good discrimination within the groups of steroids, and the tetracycline, penicillin and cephalosporin antibiotics described in the European and British Pharmacopoeias. For the cephalosporin group, separation of the thermal degradation products by paper electrophoresis is an alternative that gives slightly better results.
The technique is flexible in that there is a wide choice of thin-layer chromatographic support media, heating conditions, developing solvents and spray reagents, which facilitates its application to different classes of compounds.