PARACRYSTALLINE LATTICE DISTORTION IN CRYSTALLINE PHARMACEUTICALS DETERMINATION OF PARACRYSTALLINE LATTICE DISTORTION BY POWDER X-RAY-DIFFRACTION

The lattice distortion and size of crystallites along a particular lat tice direction in solid pharmaceuticals were determined by profile ana lysis using a peak profile of X-ray powder diffraction. The analysis w as carried out according to either the paracrystal or micro strain mod el. After correction for instrumental broadening, pure diffraction pro files of several orders of 0k0 reflections for dibasic calcium phospha te dihydrate (DCPD) and those of 0kkO reflections for griseofulvin (GR IS) were obtained. Then, the integral breadths of the pure diffraction profiles were calculated. Lattice distortion and the size of crystall ites along [0k0] of DCPD and those along [0kk] of GRIS were determined from the slope and ordinate intercept of the straight line obtained b y plotting the integral breadth against the order of reflection accord ing to the theory of paracrystalline diffraction. DCPD powders mere ch aracterized to have paracrystalline lattice distortion, in which broad ening 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 paracrystall ine lattice distortion, in which both broadening profiles of the size of crystallites and lattice distortion, are of a Cauchy (Lorentzian) s hape. The lattice distortion along [0kk] increased and the size of cry stallites decreased with the progress of grinding time. The effects of lattice distortion on physicochemical and pharmaceutical properties o f DCPD and GRIS powders were discussed.