X-ray micro-tomography - shape and orientation of single crystals
There is considerable interest in identifying the particular components of
crystal faces for powders of pharmaceutical ingredients given that they
probably play an important role in downstream unit processes. Previously, identification of the molecular composition of particular faces was restricted to large single crystals, as part of the drug registration process ,. This information is now needed in a more applied sense. Knowing the specific
molecular nature of a particular face allows the important
physico-pharmaceutical properties that stem from this to be better understood . This includes its wettability, surface adhesive properties; and the likely
fragmentation and compaction behaviour.
Recent development in high throughput methodology and
instrumentation has brought about a significant change in approach within the
pharmaceutical industry . This presents an opportunity to assess the
feasibility of simultaneous micro-tomographic shape analysis and X-ray
diffraction molecular orientation determination on single, micro-crystals. This arises because of the capability available at the new Diamond beamline, which can make such measurements down to a 5 μm beam size. In principle it becomes possible to determine molecular orientation at a very small level of size – possibly as low as 2 μm. When coupled with X-ray based micro-tomography conducted on identical crystals, the shape and olecular
orientation can be determined for surfaces of realistically sized small particles .
This will allow the investigation of a range of pharmaceutical secondary processes, such as milling, fluid energy milling (micronisation), and granulation. Furthermore it offers the chance to study mixing and agglomeration / deagglomeration at a molecular level.
Figure 1 (a) - (e) Photographs (left) at two different positions (a), (b) and the corresponding X-ray diffraction patterns (c), (d) of the small aspirin crystal (shown in red circle) on a large crystal. These photographs were captured during the experiment when the crystal was rotated to 1800 at 30 oscillations. The photograph (e) is a close-up of the one in the middle.
Author Information: Kevin Roberts, Institute of Particle Science and Engineering, School of Process, Environmental and Materials Engineering, Email: firstname.lastname@example.org
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