Drug molecules usually have different solid forms, including salts, polycrystals, eutectics, amorphous, hydrates and solvent compounds; different crystalline forms of the same drug molecule may have significant differences in properties such as crystal structure, stability, producibility and bioavailability, which directly affect the efficacy of the drug as well as its exploitability. X-ray diffraction is the main tool for studying drug crystalline forms, and the method can be used to distinguish X-ray diffraction can be used to distinguish between crystalline and amorphous states, to identify crystalline species, to distinguish mixtures and compounds, to determine the crystalline structure of drugs, to determine cell parameters (e.g. interatomic distances, ring plane distances, double-sided angles, etc.), and to compare different crystalline forms. CD Formulation offers a complete range of tests to characterize samples and then provide a comprehensive understanding of their physical properties for evaluation and drug development.
Fig.1 Diagram of single crystal diffraction equipment
Single Crystal Diffraction Testing
Single crystal diffraction is internationally recognized as the most reliable method for confirming polycrystalline patterns. It can be used to obtain in-depth knowledge of crystalline patterns by determining the crystalline configuration and molecular arrangement of each cell. Moreover, this method can be used for the determination of crystalline water/solvent and the confirmation of bonding relationships between bases and acid roots of salt-forming drugs.
Powder Diffraction Testing
Powder diffraction is the most commonly used method to study the polycrystalline form of drugs. The powder method studies not a single crystal, but the sum of numerous small crystals with random orientation. The powder X-ray diffraction pattern of each crystal is like a human fingerprint, and the intensity and distribution of diffraction lines of each crystal measured by this method have a special pattern, so that the information of crystal shape change, crystallinity, crystal structure state, and the presence of mixed crystals can be obtained by using the measured pattern. However, when applying this method, attention should be paid to the fineness of the powder, and special care should be taken not to change the crystalline shape when grinding and sieving the sample.
X-ray diffraction method has the advantages of no damage to the sample, no contamination, fast, high measurement accuracy, and can obtain a lot of information about the crystal integrity.
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