Daifi, Magda;
(2004)
The study of the characterisation and crystallisation of lactose spray dried and physical mixed products.
Doctoral thesis (Ph.D.), University College London.
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Abstract
The general aim of this thesis was to study binary spray dried composite particles of lactose with either polyvinylpyrrolidone (PVP K-25) or sodium dodecyl sulphate (SDS). The research was based on the characterisation and crystallisation of these products, with special interest directed to the stability of amorphous lactose. Lactose, PVP and SDS are used widely in pharmaceutics but have not been studied thoroughly in combination as binary systems. The spray dried (SD) and physical mixed (PM) products of lactose and PVP (K-25) or SDS were produced at varying concentrations of the latter two excipients with amorphous lactose. The effects of PVP were further studied in combination with partially amorphous lactose. Initially lactose and PVP (K-25) were studied as single components to investigate their physical properties. The effects of feed concentrate with reference to spray drying for lactose was investigated. The production of amorphous content was quantified and found to decrease with increase lactose concentration. Crystallisation kinetics using Avrami equation was determined by dynamic vapour sorption and near infrared spectroscopy (DVS-NIRS). The results showed that amorphous lactose alone and in the presence of seed crystals crystallised in a similar rate and manner. Amorphous lactose with a high quantity of crystalline material crystallised in a rapid and cooperative manner. The addition of polymer was found to increase the induction time of crystallisation of amorphous lactose and also crystal growth at concentrations higher than 10% of PVP. This delay in nucleation and inhibition of crystallisation is due to hydrogen bonding and an increase in viscosity (depicted by a raised glass transition). The PM products were relatively unaffected up until 40% polymer concentration. Partially amorphous lactose also showed a delay in the onset of crystallisation; however crystal growth was not hindered due to seeding which was found using NIRS. SDS produced the opposite effect in relation to PVP, where the increase wetting of amorphous lactose in the SD composite particle decreased both the induction and propagation time. The study of the stability of amorphous and partially amorphous lactose under the influence of PVP and SDS has been successfully investigated with the employment of a variety of analytical tools in parallel combination. However the use of the novel technique DVS-NIRS proved vital to the work accomplished.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D. |
| Title: | The study of the characterisation and crystallisation of lactose spray dried and physical mixed products. |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis Digitised by Proquest. |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10122250 |
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