PXRD diagrams

Figure 1. PXRD diagrams for (a) Zn-Cr-MH and (b) Zn-Cr-CCh-LDH (Miller indices following [12]).

Hydrothermal treatment enhances the crystallinity of the solid, which shows PXRD diagrams with sharper and more intense diffraction maxima. The crystallite size and the particle size increase, decreasing the specific surface area. The infrared (IR) spectra show sharper and more intense absorption bands, due to formation of better ordered, undistorted, solids [118]. 

For chiral drugs, it is usually necessary to apply several techniques to characterize both the enantiomer and the racemic species in order to interpret the origin of the polymorphism among the racemic species. For example, three monotropically related polymorphs of (R5)-nitrendipine were found [29]. Based on the melting phase diagram, IR spectra, and PXRD patterns, the thermodynamically stable form (I) of (R5)-nitrendipine was shown to be a racemic compound, while the other polymorphs, forms II and III, were both found to be conglomerates. Study of one of the pure... 

More recent examples of the construction of energy-temperature diagrams for drug polymorphs include those published by Schmidt and co-workers for two local anaesthetics, hydroxyprocaine hydrochloride (HPCHC, Figure 9, 11) and salicaine hydrochloride (SLCHC, Figure 9,12) [49,50]. Comprehensive solid-state analysis of these compounds included HSM, DSC, TG, FUR and Raman spectroscopy, SSNMR, PXRD, single crystal XRD and vapour pressure sorption analysis. 

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