Biomedical subjects

Steven W Booth

Publications and source records attributed to Steven W Booth.

3 recordsLinked to original sources

PubMed2002

Effect of moisture on polyvinylpyrrolidone in accelerated stability testing.

Accelerated stability studies are a common approach for predicting the long-term stability of pharmaceutical formulations. However, in this study, a slowing of dissolution was observed for a formulation following storage at elevated temperature and humidity. The moisture sorption isotherm for the binder, polyvinylpyrrolidone (PVP), shows absorption of a significant quantity of water on exposure to elevated humidity. Modulated temperature differential scanning calorimetry (mDSC) has been used to demonstrate that moisture uptake will depress the glass transition temperature (Tg) of PVP to the conditions used in accelerated stability studies. Exposure to elevated temperature and humidity resulted in a change in the PVP from the glassy to the rubbery state. This conversion produces a change in the dissolution profile. Long-term stability studies conducted at temperatures and humidities below the Tg, would not have induced this change.

Cellulose↗

PubMed2002

Quantitative analysis of mannitol polymorphs. X-ray powder diffractometry--exploring preferred orientation effects.

Mannitol is a polymorphic parmaceutical excipient, which commonly exists in three forms: alpha, beta and delta. Each polymorph has a needle-like morphology, which can give preferred orientation effects when analysed by X-ray powder diffractometry (XRPD) thus providing difficulties for quantitative XRPD assessments. The occurrence of preferred orientation may be demonstrated by sample rotation and the consequent effects on X-ray data can be minimised by reducing the particle size. Using two particle size ranges (<125 and 125-500 microm), binary mixtures of beta and delta mannitol were prepared and the delta component was quantified. Samples were assayed in either a static or rotating sampling accessory. Rotation and reducing the particle size range to <125 microm halved the limits of detection and quantitation to 1 and 3.6%, respectively. Numerous potential sources of assay errors were investigated; sample packing and mixing errors contributed the greatest source of variation. However, the rotation of samples for both particle size ranges reduced the majority of assay errors examined. This study shows that coupling sample rotation with a particle size reduction minimises preferred orientation effects on assay accuracy, allowing discrimination of two very similar polymorphs at around the 1% level.

Excipients↗

PubMed2002

Quantitative analysis of mannitol polymorphs. FT-Raman spectroscopy.

Mannitol is a polymorphic excipient which is usually used in pharmaceutical products as the beta form, although other polymorphs (alpha and delta) are common contaminants. Binary mixtures containing beta and delta mannitol were prepared to quantify the concentration of the beta form using FT-Raman spectroscopy. Spectral regions characteristic of each form were selected and peak intensity ratios of beta peaks to delta peaks were calculated. Using these ratios, a correlation curve was established which was then validated by analysing further samples of known composition. The results indicate that levels down to 2% beta could be quantified using this novel, non-destructive approach. Potential errors associated with quantitative studies using FT-Raman spectroscopy were also researched. The principal source of variability arose from inhomogeneities on mixing of the samples; a significant reduction of these errors was observed by reducing and controlling the particle size range. The results show that FT-Raman spectroscopy can be used to rapidly and accurately quantitate polymorphic mixtures.

Excipients↗