Thermal studies on the polymorphic modifications of (R,S) propranolol hydrochloride

The polymorphism of (R.S) propranolol hydrochloride was investigated by dif ferential scanning calorimetry (DSC), thermogravimetric analysis (TGA). X-r ay powder diffractometry (XRPD) and thermomicroscopy (HSM) coupled with FT- IR spectroscopy. Propranolol hydrochloride existed in three different crystalline forms, den oted as forms I, II and III, according to their decreasing melting temperat ures. Modification II was the commercial product. The forms I and III were obtained by melting form II in different experimental conditions. Form III was obtained only by solidification of the melt in the presence of an alkal i halide matrix (as a crystalline him on an alkali halide window or as powd er dispersion in a KBr pellet). Forms I and II were also obtained by crysta llization from 95% aqueous ethanol and acetone, respectively. The three for ms were easily differentiated by their IR spectra in the 3400-2000 cm(-1) r ange. The different crystalline structures of forms I and II were character ized by means of their X-ray powder diffraction patterns. (C) 1998 Elsevier Science B.V.