Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.726981
Title: Time-resolved studies of the crystallisation and dehydration of lactose and other hydrates using synchrotron X-ray and neutron powder diffraction techniques
Author: Swann, Nichola Jean
ISNI:       0000 0004 6422 9779
Awarding Body: Keele University
Current Institution: Keele University
Date of Award: 2015
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Abstract:
In-situ time-resolved synchrotron X-ray and neutron powder diffraction techniques have been applied to the study of solid state structural transitions within the organic polymorphic molecular systems of lactose, trehalose and theophylline. Diffraction techniques offer an unequalled method of polymorph identification and quantification, and have repeatedly demonstrated throughout this work that they can be utilised to follow and kinetically evaluate structural transitions in real time. The study of lactose crystallisation provides further proof of the transient ( lo::1/3) mixed crystal polymorph as the initial crystallisation product, which is then followed by the typical beta lactose and alpha lactose monohydrate phases. The formation of the (lo:: l,B) mixed crystal form has been mapped and kinetically analysed; the complex multi-step crystallisation behaviour is likely to result from the high degree of polymorphism which is displayed within the lactose system. The dehydration studies of the three systems show that dehydration kinetics can vary as a function of processing conditions and environments. Evidence of a previously undocumeuted theophylline polymorph has been observed which is accessible via the seeded dehydration of theophylline monohydrate with anhydrous theophylline form II. The best production of beta lactose from the 1-biannual dehydration of alpha lactose monohydrate to date is documented and is attained from dehydration within a hydrophobic cocoa butter environment; this transition is mediated via a crystalline phase whose identity is uncertain, yet displays a unique Bragg peak at rv 12.87° 20. Neutron diffraction techniques reveal that the water content and crystalline weight fraction of trehalose dihydrate are decoupled quantities, and the dihydrate lattice can sustain substantial water loss. These observations provide supporting evidence of a transiently stable, partially hydrated state of trehalose. In addition, the applicability of the Dl9 single-crystal diffraction beamline at the Institut Laue-Langevin in the study of hydrated powder samples is reported, demonstrating the versatility of the instrument with the capability of performing dynamic studies with a time-resolution of 15 s.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.726981  DOI: Not available
Keywords: QC Physics
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