My colleague Paul Kippax was asked recently to contribute to an article for Pharmaceutical Technology about particle characterization, so it was with some interest that I turned to the finished piece, published last month. ‘The Power of Particle Characterization’ is a nice review that focuses on two key points: the importance of particle characterization for this industry (which explains the title I guess) and the development of techniques that can deliver the necessary information – a process that continues today.

Data to drive pharmaceutical development

Whether an active pharmaceutical particle is inhaled, ingested or injected, its size is central in determining so many things – uptake by the body, deposition site, dissolution rate, and/or speed of absorption. Furthermore particle size influences crucial processing behaviour, such as the ease with which a powder flows, its compressibility and segregation.

Particle size information alone though doesn’t hold all the answers. As analytical techniques have developed it is now possible to investigate the impact of other factors in more detail. Particle shape, for example, is now recognised as being similarly important for both product performance and ease of manufacture.

The article highlights the fact that pharmaceutical industry is now using a number of different particle, and indeed powder, characterization techniques to satisfy its thirst for knowledge.

Developing particle characterization technology

One of the simplest and most intuitive ways of characterizing a particle is to look at it – and microscopy has long been a central analytical tool. Today though we have automated imaging techniques that measure more particles, faster, and without any operator bias. These instruments are driving our understanding of the impact of particle shape, and in combination with spectroscopic techniques they provide rich information on size, shape and composition.

On the particle sizing front numerous techniques have been introduced over the years, as well as the long-established sieving, sedimentation and electrozone sensing. All produce different numerical descriptors of size and all have advantages and limitations. Increasingly though laser diffraction s the pharmaceutical industry’s first choice for routine particle sizing because it’s fast, non-destructive, highly reproducible and full automated.

I can recommend the Power of Particle Characterization and also a white paper on the evolution of laser diffraction for anyone interested in finding out more. Or if you have a detailed query or comment please don’t hesitate to contact me.