Paracrystalline Lattice Distortion in Crystalline Pharmaceuticals Determination of Paracrystalline Lattice Distortion by Powder X-Ray Diffraction.

Abstract

The lattice distortion and size of crystallites along a particular lattice direction in solid pharmaceuticals were determined by profile analysis using a peak profile of X-ray powder diffraction. The analysis was carried out according to either the paracrystal or micro strain model. After correction for instrumental broadening, pure diffraction profiles of several orders of 0k0 reflections for dibasic calcium phosphate dihydrate (DCPD) and those of 0kk reflections for griseofulvin (GRIS) were obtained. Then, the integral breadths of the pure diffraction profiles were calculated.Lattice distortion and the size of crystallites along [0k0] of DCPD and those along [0kk] of GRIS were determined from the slope and ordinate intercept of the straight line obtained by plotting the integral breadth against the order of reflection according to the theory of paracrystalline diffraction. DCPD powders were characterized to have paracrystalline lattice distortion, in which broadening profiles of both the size of crystallites and lattice distortion are of a Gaussian shape. The lattice distortion along [0k0] increased, while the size of crystallites scarcely decreased with the progress of grinding time. GRIS powders were characterized to have paracrystalline lattice distortion, in which both broadening profiles of the size of crystallites and lattice distortion, are of a Cauchy (Lorentzian) shape.The lattice distortion along [0kk] increased and the size of crystallites decreased with the progress of grinding time.The effects of lattice distortion on physicochemical and pharmaceutical properties of DCPD and GRIS powders were discussed.