PREFERRED ORIENTATION OF CRYSTALLITES IN TABLETS .5. PATTERN-FITTING PROCEDURE FOR THE DETERMINATION OF STRENGTH OF PREFERRED ORIENTATION OF CRYSTALLITES

A pattern-fitting procedure was described to determine the strength of preferred orientation of crystallite in tablets using X-ray powder di ffraction data. This method is based on the pattern-fitting crystal st ructure refinement method which also uses powder diffraction data. Obs erved X-ray scattering intensities were fitted to analytic expression including some fitting parameters, namely peak positions, peak widths, background intensities and preferred orientation. All fitting paramet ers were optimized by non-linear least-squares procedure. Then the str ength of preferred orientation of crystallites was evaluated from the magnitude of preferred orientation parameter. Aspirin was used for the sample, and though aspirin crystallites showed little preferred orien tation in powders, they showed marked preference in tablets. The magni tude of preferred orientation parameter increased with increasing comp ression pressure of tablet. This indicated that aspirin crystallites s howed stronger preferred orientation in tablets prepared under higher compression pressure.