Johnson, Fiona Ann; (1995) The physico-chemical characterisation of alginate raft systems. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Alginate rafts are used in the treatment of reflux oesophagitis and act by forming a buoyant layer on the stomach contents. The aim of this project was to characterise the raft components and investigate the way in which the components affect the properties of the rafts. The chemical structure of the alginates was investigated using nuclear magnetic resonance (NMR) and circular dichroism (CD). Rheological properties of the solutions were studied both at the concentrations used in the raft forming mixtures and at lower concentrations for the determination of intrinsic viscosity. The properties of gels formed either by the addition of divalent cations or by the action of acid on the solutions were investigated by the use of dynamic mechanical analysis (DMA) techniques. The effect of varying the divalent ion used in gel formation and the differences between alginate samples were studied using DMA. A novel technique for the characterisation of alginate rafts was developed using a texture analyser. The effect of formulation variables on the raft was then studied using the method described. The results show that the properties of the raft are dependent on the alginate used, the bicarbonate included in the formulation and the presence of additional divalent cations. The strength of the acid in which the raft forms also affects the properties of the raft. It was also shown that the characteristics of the raft are not solely dependent on the properties of the individual components, but the interaction between the components also affects the overall properties of the raft formed. This work suggests ways in which the performance of alginate rafts may be measured to give an understanding of how the characteristics may be controlled by the variation of the components of the raft forming mixture.

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