X-RAY-POWDER DIFFRACTION PROFILE FITTING IN QUANTITATIVE-DETERMINATION OF 2 POLYMORPHS FROM THEIR POWDER MIXTURE

X-ray powder diffraction profile fitting analysis has been developed to reveal the relative amounts of two prazosin hydrochloride polymorphs from their powder mixture. Diffraction profiles were measured from carefully prepared samples of a pure alpha-prazosin, delta-prazosin and their mixed powder having weight fractions of alpha-prazosin ranging from 0.5 to 10%. With the aid of mathematical profile fitting, the background intensity level of delta-prazosin and the integrated intensity of the peak caused by alpha-prazosin have been determined. As a result, a surprisingly good detection sensitivity of 0.5% has been reached, although the peak of alpha-prazosin used in determination overlapped somewhat with that of delta-prazosin. Therefore, it has been concluded that this technique is generally able to reveal relative amounts of two crystalline polymorphs from their powder mixture to a sensitivity of 0.5-1% depending on the state of peak overlapping.