& A thin-layer chromatography (TLC) technique was used to separate the thermal decomposition product of ranitidine hydrochloride. Three samples of standard were heated in thermostat for 5 d in 60 C, 8 d in 80 C, and 2 hr in 100 C. The reagents used as mobile phases were: dimethyl sulfoxide (DMSO), acetonitrile, methanol, 25% ammonia, 2-propanol, and 2-methoxyethanol in a wide range of concentrations 0-100% (v=v). Silica gel 60 F 254 HPTLC plates acted as the stationary phase. The usefulness of various mobile phases to separate ranitidine and products of its thermal decomposition was demonstrated as well as the thermodynamic dependence has been shown.