Fast and direct colloidal stability determination
Patrick O'Hagan, Amanda Coder, Greg Pokrajac and Heather Helsing¹; Pharmaceutical Formulation and Quality.
Abstract: Centrifugal separation analysis can be used on concentrated samples to directly measure stability and separation within minutes. Everyday we use products that are formulated as emulsions. These include paints, foods, cosmetics and pharmaceuticals. Emulsions are also used as intravenous drug delivery vehicles and in parental nutrition. Many p[harmaceutical active ingredients are formulated as emulsions so particle size is reduced enough to make a consistent and stable product, in which the particles do nto coalesce during thier shelflife. An emulsion that doesn't change under accelerated environmental conditions is said to be colloidally stable. Shelflife expectancy depends on the product and how quickly it is expected to be used. Even as a product is on the shelf, dispersed particles are in motion. Particles denser than the suspending medieum tend to settle to the bottom of the container; those less dense than the suspending medium nigrate to the top. The rate at which they do depends on the size of the particles and the interaction between them. Since quality often varies, the stability of emulsions must be constantly evaluated by performing shelf-life and particle size tesing. Shelflife measures stability directly but can take days or weeks to perform, even when accelerated at high temperatures. Existing particle sizing have a significant drawback. Particle size analysis is fast, but not a direct measurement of stability since the correlation between particle size and stability is often poor. Furthermore, most commercial particle size analyzers are based on light scattering, so require considerable dilution to measure, this affects the size of the particles and their interaction
Key words: Colloidal stability • Shelf life test • Emulsions • Suspensions • Intravenous drug delivery • Parental nutrition • Concentrated dispersions • LUMiFuge
¹ Particle Sizing Systems, Fort Richie, Florida.Contact us
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