Simple thin-layer chromatographic method for the investigation of six related compounds in flurazepam hydrochloride and its capsules

A simple and rapid thin-layer chromatographic procedure is presented for the separation and tentative identification of flurazepam hydrochloride and its six related impurities in bulk samples and capsules. A methanolic sample solution is applied to a plate of silica gel containing a fluorescent indicator, which is developed once with a basic quaternary solvent system. Spots are visible under a short wavelength UV lamp, with a limit of detectability ranging from about 62.5 ng (related compound B) to 500 ng (related compound C). The proposed procedure shows several advantages over the related compounds test of the United States Pharmacopeia.