Abstract
Crystallinity in a drug has been recognized as an important factor affecting stability, bioavailability and scaling-up of processing operations. In the field of pharmaceutical technology, crystallinity has not yet been studied by Ruland's method, one of the X-ray diffraction methods. The main reason why it is not used may be that extensive and time-consuming calculations are required. We have developed a modified Ruland's method for determining the degree of crystallinity and the disorder parameter from a powder diffraction pattern of a single sample, suitable for a routine preformulation test. The degrees of crystallinity and the disorder parameters in several samples were measured by Ruland's method and the effects of integral upper limits, integral lower limits, and normalization constants on the results were examined. The integral upper limits seemed to affect the results calculated from the data of a single sample very much, and so did the separation of the crystalline scattering intensity from the total scattering intensity. We completed a computer program for the automated separation of the noncrystalline scattering intensity and the determination of integral upper limits with a single sample. The results can be obtained from a single sample with satisfactory accuracy for the practical purpose of pharmaceutical technology.
