Development of computational tools to assist phase identification by X-ray diffraction on polycrystalline materials

• Grant number: 15/17101-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2015
• End date: August 31, 2016
• Field of knowledge: Interdisciplinary Subjects
• Principal Investigator: Julia Sawaki Tanaka
• Grantee: Lucas Rossetto Agra
• Host Institution: Instituto de Química (IQ). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil

Abstract

Often, the drug efficiency depends on the crystal structure of the active ingredient present in the raw material used in its processing. A substance, on the other hand, can crystallize in different crystal structures (polymorphs), despite having the same chemical structure. The polymorphs may have different physical and chemical properties and different bioavailability. Thus, it becomes important to study the crystalline forms of the drugs (polymorphs) both in raw material and the finished drugs. Among the techniques for evaluating polymorphism in raw materials and pharmaceuticals, the X-Ray Powder Diffraction (XRPD) is an interesting option that allows qualitative and quantitative analysis of solid mixtures. Often, it is only needed to identify the phases present in a raw material or pharmaceutical product. For these cases, it can be used databases such as the ICDD-PDF, Pearson's Crystal Data, Crystallography Open Database, and Cambridge Structural Database. However, these databases do not have the XRD data of all known polymorphs. In situations where these databases fail, what one can do is to generate the diffraction pattern of the substance based on patent or scientific articles information and compare it with the observed diffraction pattern of the material to identify the present crystalline phases. To enable this type of analysis it has been developed software called JST-XRD that generates XRD diffraction patterns from the data (2q x I) or (d x I) of the substances, obtained in patents and scientific articles. The software generates the diffractogram and allows you to save the image and the values (x, y) of all points of the generated diffractogram. The software enables also to overlay several generated diffraction patterns with the observed diffraction pattern of the material being analyzed. Sometimes, the data (2q x I) or (d x I) are not found in patents and scientific articles, however, photocopies of diffractograms or scanned images of these diffractograms are provided and may be useful for identification, since a table (2q x I) or (d x I) can be extracted from them. The phases identification in materials with substances whose diffraction data are only available in the form of image is currently carried out manually, using the Microsoft PowerPoint® program and superimposing the images of the diffraction patterns transformed into the transparent background. Several handling is required to put the XRD patterns on the same scale to enable identification. Another problem found in this form of analysis is the provided image quality, for example in a patent, which presents a lot of noise or very low copy quality. Another way currently used to extract the image data is with the use of a ruler to measure the positions and intensities of the peaks. To make this analysis more dynamic, it is interesting to develop software that allows the extraction of such information in less time and more precisely, and which enables the inclusion of this information in the JST-XRD program. The objective of this work is to develop a computational tool to analyze images of diffraction patterns and extract data of position versus intensity of the Bragg peaks. It is also objective of this proposal, the training of human resources with knowledge in scientific programming and crystallography. In the development of the software, it will be used the Integrated Development Environment (IDE) Lazarus which is an open and free code IDE that allows visual and object-oriented programming based on the Free Pascal compiler. (AU)