X-ray powder diffraction is a method used for analysing crystalline materials and identifying phases in unknown samples. The method is based on the diffraction of X-rays on electrons, where diffraction occurs only if all the conditions of Bragg’s law are fulfilled. When a crystalline sample is recorded on a diffractometer, a characteristic powder image or diffractogram is obtained, which is then analysed using different computer programmes.
To understand advantages and limitations of the method, I chose to analyse twelve different antihypertensive medicines. I prepared the samples, sent them for recording and performed a qualitative phase analysis using the recorded diffractograms. The analysis was enabled by using three different computer programmes. Firstly, I used X’Pert HighScore Plus to open the recorded diffractograms and compare them with each other, and then I used Crystallographica Search-Match to identify the phases in the samples. For some samples, I had to use program PDF+ to obtain more information about some substances, which I then entered into the CSM program. Based on the similarity of the diffractograms and the content of the same phases, I divided the samples into five groups. Finally, I compared my results with the declarations of the medicines and found out that I was able to identify the main active substances in almost all samples. The remaining excipients and some main active substances that were not identified were those that were present in the samples in too low percentage or had amorphous structure that could not be determined by X-ray powder diffraction.
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