Powder X-Ray Diffractometry

R. Jenkins and R. L. Snyder, Introduction to X-ray Powder Diffractometry, John Wiley Sons, Inc., New York, 1996. 

Crystalline material will diffract a beam of X-rays, and X-ray powder diffractometry can be used to identify components of mixtures. These X-ray procedures are examples of non-destructive methods of analysis. 

Vol. 138. Introduction to X-Ray Powder Diffractometry. By Ron Jenkins and Robert L. Snyder... 

Overviews [321] and monographs [322,323] dealing with X-ray powder diffractometry are available. 

X-ray powder patterns can be obtained using either a camera or a powder diffractometer. Currently, diffractometers find widespread use in the analysis of pharmaceutical solids. The technique is usually nondestructive in nature. The theory and operation of powder diffractometers is outside the purview of this chapter, but these topics have received excellent coverage elsewhere [1,2]. Instead, the discussion will be restricted to the applications of x-ray powder diffractometry (XPD) in the analysis of pharmaceutical solids. The U.S. Pharmacopeia (USP) provides a brief but comprehensive introduction to x-ray diffractometry [3],... 

X-ray powder diffractometry is widely used for the identification of solid phases. The x-ray powder pattern of every crystalline form of a compound is unique, making this technique particularly suited for the identification of different polymorphic forms of a compound. The technique can also be used to identify the solvated and the unsolvated (anhydrous) forms of a compound, provided the... 

X-ray powder diffractometry is widely used to determine the degree of crystallinity of pharmaceuticals. X-ray diffractometric methods were originally developed for determining the degree of crystallinity of polymers. Many polymers exhibit properties associated with both crystalline (e.g., evolution of latent heat on cooling from the melt) and noncrystalline (e.g., diffuse x-ray pattern) materials. This behavior can be explained by the two-state model, according to which polymeric materials consist of small but perfect crystalline regions (crystallites) that are embedded within a continuous matrix [25]. The x-ray methods implicitly assume the two-state model of crystallinity. 

X-ray powder diffractometry offers a unique advantage in the quantitative analyses of mixtures consisting of the anhydrous and hydrated forms of a compound. In order to appreciate this, it is necessary to understand the interaction of water with solids. There are four possible states of water in solids [48] (1) adsorbed on the solid surface, (2) absorbed or dissolved in the solid, (3) associated... 

X-ray powder diffractometry is a relatively straightforward technique for phase identification. There are, however, numerous sources of error in quantitative XPD. The issues that are of greatest relevance to pharmaceutical systems are enumerated in the following. 

X-ray powder diffractometry can be used to study solid state reactions, provided the powder pattern of the reactant is different from that of the reaction product. The anhydrous and hydrated states of many pharmaceutical compounds exhibit pronounced differences in their powder x-ray diffraction patterns. Such differences were demonstrated earlier in the case of fluprednisolone and carbamazepine. Based on such differences, the dehydration kinetics of theophylline monohydrate (CvHgN H20) and ampicillin trihydrate (Ci6H19N304S 3H2O) were studied [66]. On heating, theophylline monohydrate dehydrated to a crystalline anhydrous phase, while the ampicillin trihydrate formed an amorphous anhydrate. In case of theophylline, simultaneous quantification of both the monohydrate and the anhydrate was possible. It was concluded that the initial rate of this reaction was zero order. By carrying out the reaction at several... 

Clark, R. J. H., Curri, L., Henshaw, G. S., and Laganara, C. (1997). Characterization of brown-black and blue pigments in glazed pottery fragments from Castel Fiorentino (Foggia, Italy) by Raman microscopy, X-ray powder diffractometry and X-ray photoelectron spectroscopy. Journal of Raman Spectroscopy 28 105-109. 

M. Otsuka, F. Kato, Y. Matsuda and Y. Ozaki, Comparative determination of polymorphs of indomethacin in powders and tablets by chemometrical near-infrared spectroscopy and X-ray powder diffractometry, AAPS PharmSciTech, 4, 147-158 (2003). 

The SiC-coated diamond particles can be characterized by X-ray powder diffractometry. The diffraction peak appears at 35.6° which is assigned as the /J-SiC (111) plane. 

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