techniques for emulsion characterization
The required emulsion characterization and control is provided by Process Analytical Technology (PAT) in a range of products:
- Active Pharmaceutical Ingredients (APIs) liquid formulations, such as topical anesthetics consisting of oil-in-water emulsions and lipid emulsions
- Personal care and cosmetic products, such as emulsions in hand-creams, lotions, and sunscreens
- Agrochemicals formulations
- Emulsions in the oil industry, consisting of crude oil and water
- Food emulsions, such as mayonnaise, infant formula, ice cream, and beverages
Emulsions are dispersions of liquid droplets in another non-miscible continuous liquid that requires long-term stability for most applications. To this purpose, emulsifiers are used to modify surface chemistry, stabilize the droplets created through a shear-induced process, and prevent droplets from coalescing or flocculating. On the other hand, demulsifiers may be used to destabilize emulsions for better separation when the emulsion stability is undesirable.
Controlling these properties often poses challenges for those tasked with optimizing product quality and process efficiency.
Characterizing droplet size effectively allows scientists and engineers to solve process bottlenecks and improve product quality. Traditionally, scientists have relied on offline particle size analyzers to perform pharmaceutical emulsion and suspension characterization. Offline analysis typically requires sample preparation and sample dilution prior to analysis. In the case of using PAT for emulsions, this can significantly change the droplet size in an emulsion sample within the time required for preparation and analysis.
This PAT for emulsions paper discusses how to track the rate and degree of change of droplet size and count, as they naturally exist in process without the need for sampling or sample preparation. In-process measurement of droplets can not only reduce the error associated with offline sampling, but also provide real-time information about how droplets behave under changing process conditions for better Quality by Design (QbD).
Four PAT for emulsions case studies are presented:
- Achieve Optimal Droplet Size Through Process Understanding
- Monitoring of Multi-Phase Systems (Pickering Emulsions)
- Scale-up with Real Time Process Trends
- Monitoring Different Product Lines in Manufacturing
Direct inline measurements of emulsions, under dynamic and changing process conditions, provide unique process understanding that scientists can use to make evidence-based decisions quickly. Process analytical technology for emulsions can also be implemented as part of a Quality-by-Design (QbD) approach, and as a method to ensure consistency of the chosen process during scale-up and manufacture.