Non-invasive infra-red spectrometry can provide scientists with improved quality checks for pharmaceutical production.

Enormous efforts in the pharmaceutical industry are currently being made to improve the efficiency of manufacturing procedures, aiming to ensure smooth, high-quality and continuous processes. With this in mind, scientists at the University of Strathclyde, Glasgow, UK, have recently developed a method for looking at how powders blend together during the process itself.

Up until now, most methods of looking at powder mixtures required the blending process to be stopped. David Littlejohn and colleagues have now developed a non-invasive NIR (near infra-red) spectrometry method that enables this monitoring to be done in real time. Information on the sample can be collected by measuring the NIR spectra through a window in the reaction vessel, or via a probe in the powder mixture. The movement of particles has an influence on the NIR spectra measured and in the past, scan times have been too long to study the sample accurately. Littlejohn's method has a short scan time and not only examines the dynamics of powder blending, but can also provide quantitative information about the ingredients, all while the sample moves.

The method also monitors any possible changes in particle size. This point may prove to be very important for future industrial use, as on this scale, particle cohesion effects have more effect on the blending and time taken for a mixture to reach homogeneity. Littlejohn said that the key advantage of this technique is being able to provide a combination of these different types of information. 'This method will add to the toolbox of techniques that are available, to build further quality checks into a production process,' he said.

The team are optimistic that the monitoring method will be successful when used on a larger scale process. 'The methodology described has been applied successfully to a ribbon blender at industrial plant scale, indicating the transferability of the procedure,' said Littlejohn. His team are currently looking at alternative methods of monitoring the blending process, including Raman spectroscopy and acoustic techniques.

May Copsey