Mastersizer plays role in development of new technology for manufacturing emulsions

Emulsions are of growing significance in the pharmaceutical, cosmetics, toiletries and food industries. However, current production methods are relatively inefficient and are prone to problems of scale-up from laboratory to pilot plant. Batch to batch reproducibility can also be unreliable in large-scale manufacture.

At the University of Leeds in the UK, the Engineering Colloid Group led by Professor Richard Williams is working with industrial partners on the development of a new emulsion manufacturing method known as Crossflow Membrane Emulsification (XME). Critical to the success of this development has been the ability to measure droplet size distributions easily, initially using the Malvern Mastersizer S, and more recently the new Mastersizer 2000.

New concept Crossflow membrane emulsification offers significant advantages over traditional manufacturing methods in controlling the size and size distribution of emulsion droplets, and it is independent of the scale of manufacture. The concept is simple and involves injecting one phase through a porous substrate (membrane) in such a way that droplets formed at the end of the pores at the membrane surface come into contact with the second (continuous) phase. The membrane can be formed as a tube, with continuous phase pumped crossflow to scour the surface. Varying the transmembrane pressure and crossflow velocity enables close control of the size distribution of the emerging droplets and determines the production rate.

Pilot scale Following initial work that studied fundamental process parameters controlling droplet formation, and went on to address practical issues such as membrane selection, pore size and porosity, pilot scale studies using oil in water emulsions served as models pertaining to cosmetics applications.

Initially the Mastersizer S was used for fine measurement of droplet size distribution on samples taken regularly during the emulsification process. Subsequent work has been undertaken using the Mastersizer 2000 which was selected for its ability to measure reliably across a wide range of particle sizes, from 0.02µm to 2000µm. The Mastersizer 2000 also works to user-defined Standard Operating Procedures, ensuring consistent sample handling and measurement whichever operator makes the analysis, and allowing the instrument to be used with minimal training.

A sample of the data generated can be seen in Figure 1, which shows the effect of crossflow velocity on droplet size distribution, one of many parameters studied in the pilot scale process.

Scale up Industrial scale production of emulsions using this technique is now under investigation and the expectation is that it will find widespread application in a range of manufacturing industries.

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