Crystallization Kinetics of Amorphous Griseofulvin by Pattern Fitting Procedure Using X-Ray Diffraction Data
- 232 Downloads
A pattern fitting procedure using X-ray powder diffraction patterns was applied to study the crystallization kinetics of amorphous griseofulvin. From the optimized parameters obtained by pattern fitting, a change in the quantity and quality of griseofulvin crystals with crystallization was also investigated.
Materials and Methods
Amorphous griseofulvin was prepared by cooling the melts followed by pulverization. X-ray diffraction patterns of amorphous griseofulvin were repeatedly measured every 20 h. The observed pattern was separated into crystalline diffraction intensity and amorphous scattering intensity by the nonlinear least-squares procedure.
The fitting between the observed and simulated diffraction patterns was satisfactorily independent of the degree of crystallinity. Since a good linear relationship was found in a plot of amorphous scattering intensity against crystalline diffraction intensity, the degree of crystallinity can be determined according to Hermans’ method. The diffraction peak width increased with higher diffraction angles with crystallization. The crystallization was biphasic: fast and slow crystallization with the growth of low disordered crystals and disordered crystals, respectively.
The pattern fitting procedure is a powerful tool to analyze the X-ray diffraction patterns of semicrystalline materials. This procedure can simultaneously analyze the degree of crystallinity and crystal disorder in semicrystalline samples during crystallization.
Key wordscrystallinity crystallization pattern fitting powder X-ray diffraction
- 4.R. Surena and R. Suryanarayanan. Quantitattion of crystallinity in substantially amorphous pharmaceuticals and study of crystallization kinetics by X-ray powder diffractometry. Powder Diff. 15:2–6 (2000).Google Scholar
- 12.R. Delhez, T. H. de Keijser, J. I. Langford, D. Louer, E. J. Mittemeijer, and E. J. Sonneveld. Crystal imperfection broadening and peak shape in the Rietveld method. In R. A. Young (ed.)., The Rietveld Method, Oxford University Press, New York, 1993, pp. 132–166.Google Scholar
- 15.G. Malmos, A. Wagner, and L. Maron. (2S,6′R)-7-chloro-2′,4,6,-trimethoxy-6′-methyl-spiro-(benzofuran-2(3H),2-(2′)cyclohexane)-3,4′-dione C17H17ClO6. Cryst. Struct.Commun. 6:463–470 (1977).Google Scholar
- 18.R. A. Young. Introduction to the Rietveld method. In R. A. Young (ed.)., The Rietveld Method, Oxford University Press, New York, 1993, pp. 1–38.Google Scholar
- 23.H. P. Klug and L. E. Alexander. X-ray Diffraction Procedures for Polycrystalline and Amorphous Materials, 2nd edn. Wiley, New York, 1974, pp. 618–708.Google Scholar
- 24.R. Hosemann and S. N. Bagchi. Direct Analysis of Diffraction by Matter, North Holland, Amsterdam, 1962.Google Scholar