Ground and native crystals: comparison of compression capacity and dissolution rate

Abstract Some authors such as Huttenrauch have suggested that the trauma to crystals during grinding may induce defects in these crystals causing disorder in the crystal lattice. This decrease in crystallinity should improve compression capacity and dissolution rate, independently of any particle-size considerations. We have tried to study this hypothesis, using two types of crystals: aspirin and lactose α -monohydrate. For precise and significant comparison, native and ground crystals must have the same particle size. Fine native crystals were separated by sieving from a recrystallized batch. Fine ground crystals were prepared by grinding the separated coarser crystals. Very fine crystals adsorbed on the crystal surface were removed by pneumatic sieving (Alpine®). These two types of crystals were then studied as regards their morphology, crystalline state, compression capacity, and dissolution properties. From this study, it seems that no significant compression capacity improvement is to be observed when native and ground crystals of the same particle size are compared. A slight increase in the dissolution rate of ground aspirin crystals might be ascribed to surface defects improving crystal wetting. Disorder seems to occur only at the crystal surfaces.