Influence of process parameters on fluidised hot-melt granulation and tablet pressing of pharmaceutical powders

This study investigates the influence of process parameters on the fluidised hot melt granulation of lactose and PEG 6000, and the subsequent tablet pressing of the granules. Granulation experiments were performed to assess the effect of granulation time and binder content of the feed on the resulting granule properties such as mass mean granule size, size distribution, granule fracture stress, and granule porosity. These data were correlated using the granule growth regime model. It was found that the dominant granule growth mechanisms in this melt granulation system were nucleation followed by steady growth (PEG 10–20% w/w). However, with binder contents greater than 20% w/w, the granulation mechanism moved to the “over-wet massing” regime in which discrete granule formation could not be obtained. The granules produced in the melt fluidised bed process were subsequently pressed into tablets using an industrial tablet press. The physical properties of the tablets: fracture stress, disintegration time and friability were assessed using industry standards. These analyses indicated that particle size and binder content of the initial granules influenced the mechanical properties of the tablets. It was noted that a decrease in initial granule size resulted in an increase in the fracture stress of the tablets formed.

Elucidation of the controlling steps of reactive dyes adsorption on activated carbon

In this work, the rate-limiting steps of reactive dye adsorption onto FS-400 activated carbon were elucidated through the investigation of adsorption kinetics. These studies initially revealed that only 20% of the available adsorption capacity was achieved during the first 6 h of mixing. Kinetic profiles showed that the adsorption process was mainly controlled by external diffusion during the first 30 min of the reaction, after which internal diffusion controlled the process. The interruption test method identified the rate-limiting steps; the results showed that sorption of reactive dyes onto FS-400 was mainly controlled by internal diffusion. Furthermore, the external and internal diffusion coefficients and the desorption rate decreased after the interruption period. The same parameters increased when the solution temperature was raised. The thermodynamic parameters studied showed that the adsorption of reactive dyes onto activated carbon was endothermic and is mainly controlled by internal diffusion with a minor effect of external diffusion.

A method of false coincidence removal from measurements of quadruple coincidences between two photoelectrons and two photoions generated in molecular double photoionization

The removal of false coincidences from measurements of coincidences between two photoelectrons and one or two ions formed in molecular double photoionization is described. False coincidences arise by several mechanisms; experimental procedures and mathematical formulae required to remove all the different false coincidence contributions are described. Sample spectra taken of the double photoionization of carbon dioxide are presented to illustrate the method of false coincidence subtraction.