Surface properties affect pharmaceuticals by influencing physical behaviour, which can cause problems for both formulation and medication. Poorly water soluble compounds are often modified with polymer surfactants. The presence of amorphous material, due to its effect on dissolution rate, can modify the bioavailability of a compound. This thesis reports the novel application of X-ray Absorption Spectroscopy (XAS) and X- ray Photoelectron Spectroscopy (XPS) to surface related pharmaceutical problems. XAS is sensitive to bond angles, local symmetry and oxidation states and XPS provides information on local chemical environment. Both have a probing depth <10 nm in the soft X-ray range. It is shown that XAS and XPS are capable of determining the physicalcoverage of ultra-thin polymer coatings. In situ XAS confirmed they formraft-like structures on the drug surface. Adsorbed water could also be de-tected on the surface and this corresponds to improvement in dissolutionrate, which implies an improvement in bioavailability. XAS was capableof distinguishing between amorphous and crystalline batches of two drugsat the surface. It was also able to detect a nanoscale amorphous overlayerin predominantly crystalline micronised batches of the drug. High relativehumidity was shown to recrystallise both the amorphous and micronisedbatches. X-ray PhotoElectron Emission Microscopy (XPEEM) of pharma-ceutical compounds was attempted but, due to the higher beamflux required,sample damage and charging effects were too great to draw any meaningfulconclusions at this time.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:606791 |
| Date | January 2008 |
| Creators | Booth, Alastair Murray |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://www.manchester.ac.uk/escholar/uk-ac-man-scw:190668 |
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