Oyebola, Mosunmola Titilayo; (2004) Investigations into the reproducibility of powder flow measurements and their relevance for pharmaceutical dosage form manufacture. Doctoral thesis (Ph.D.), University College London.

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Abstract

In the pharmaceutical industry, powder flow assessment methods are of great interest for the development and manufacture of solid dosage forms. Methods providing reproducibility, yet which are easy to perform, are sought. The aim of the thesis was to evaluate methods to determine powder flow for their ability to detect variability in flow, reproducibility of the results and ease of use. The operation and performance of the rotational split-level shear tester using a standard cell was evaluated by studying the flow and failure properties of pregelatinised starch, α-lactose monohydrate, precipitated calcium carbonate, microcrystalline cellulose type 105 and powder fractions of the first two of these powders. The results indicated that reproducible and reliable flow properties could be obtained using a set of derived parameters of operation. The instrument was able to detect differences in shear properties due to differences in particle size when using size- fractionated powder samples. An influence of relative humidity of the air (35 - 75 %) on the shear properties, however, was not evident. The results obtained for the powders in relation to static and dynamic packing demonstrated that the use of the Mohammadi and Hamby model (compaction constant, T) led to a better/distinct ranking of powders than the commonly employed Carr's compressibility index, and that the use of a classical tap volumeter as opposed to the fast tapping technique described in the European Pharmacopoeia enhances packing of powders. Pre-drying the powder prior to particle density measurements led to better values being obtained as indicated by the statistical evaluation of the pre and post - drying data. The critical orifice diameter measurement led to a different ranking of the powders compared to the other methods of powder flow evaluation. The studies have shown that the rotational split-level shear tester gave the most useful data which were reproducible and able to differentiate between the properties of the powders.

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