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X-ray Powder Diffraction in Conservation Science: Towards Routine Crystal Structure Determination of Corrosion Products on Heritage Art Objects
Published on: June 8, 2016
X-ray powder diffractometry in combination with principal component analysis--a tool for monitoring solid state
Karin Kogermann1, Peep Veski, Jukka Rantanen
1Department of Pharmacy, Faculty of Medicine, University of Tartu, Estonia. kkogermann@gmail.com
Summary
Ball-milling techniques were used to prepare amorphous piroxicam (PRX). Low-temperature ball-milling effectively produced amorphous PRX, while room-temperature methods induced phase transformations in anhydrous PRX forms.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Pharmaceutical Sciences
Background:
- Piroxicam (PRX) exists in multiple crystalline forms, impacting its bioavailability.
- Amorphous forms often exhibit enhanced solubility and dissolution rates compared to crystalline counterparts.
- Controlling solid-state transformations during preparation is crucial for pharmaceutical applications.
Purpose of the Study:
- To investigate the structural changes and phase transformation kinetics of piroxicam during ball-milling.
- To explore the efficacy of different ball-milling conditions (temperature) for preparing amorphous piroxicam.
- To elucidate the influence of thermal and mechanical stress on piroxicam crystalline forms.
Main Methods:
- X-ray powder diffractometry (XRPD) for structural analysis.
- Raman spectroscopy combined with principal component analysis (PCA) for kinetic studies.
- Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) for thermal behavior assessment.
- Ball-milling at room and low temperatures, quench cooling of melt for amorphisation.
Main Results:
- Ball-milling of anhydrous PRX forms at room temperature led to partial amorphisation, formation of anhydrous PRX form III (PRXAH III), and its transformation to anhydrous PRX form I (PRXAH I).
- Ball-milling of PRX monohydrate (PRXMH) at room temperature induced partial dehydration and amorphisation.
- Low-temperature ball-milling effectively produced amorphous PRX from anhydrous forms and partially amorphous PRX from PRXMH, attributed to water's plasticizing effect.
Conclusions:
- Ball-milling is a viable method for inducing amorphisation and phase transformations in piroxicam.
- Low-temperature ball-milling is more effective for achieving high yields of amorphous piroxicam, especially from its monohydrate form.
- Understanding the interplay between mechanical stress, temperature, and hydration state is key to controlling piroxicam solid-state forms.
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