Complex signals difficult to interpret

If the positive aspects of the use of vibrational spectroscopy are undeniable, this method also has some drawbacks. “The signal it supplies is very complex to interpret. It provides much chemical and physical information for all the compounds of the analysed matrix. Very sophisticated chemometric tools are therefore required to exploit this information and extract the information that is of interest to us”, explains Eric Ziemons. “The use of chemometrics therefore requires extra expertise in order to be able to interpret the results”. Another drawback of near-infrared and Raman spectroscopy is that they do not enable detection of compounds whose content is less than 1%.

Not perfect but sufficiently convincing, the vibrational techniques have convinced the pharmaceutical industry and many firms have used these techniques to control their raw materials, products and processes. The Analytical Chemistry Laboratory of the University of Liege regularly collaborates with pharmaceutical companies seeking expertise in this area. Lastly, in collaboration with the company UCB, Pierre-François Chavez, a doctoral student at the laboratory focussed on the implementation of vibrational spectroscopy to control a drug produced by the company. His work was aimed at improving the quality of a tablet with the help of an approach based on the “Design Space”, near-infrared spectroscopy and Raman imaging. The results of this study were recently published in the International Journal of Pharmaceutics (1).  

In the context of this same collaboration between the researchers from Liege and UCB, a second study was also published in Talanta (2). The aim of this work was to follow the content of active ingredient, that is to say the therapeutic compounds in the tablets during their production. “The results of this study demonstrate the relevance and analytical performances of near-infrared spectroscopy as a “PAT” tool for controlling the content of active ingredient of the tablets during the compression stage”, reveals Eric Ziemons.



In order to further develop the techniques of vibrational spectroscopy in the Analytical Chemistry Laboratory, the researcher aims to improve data processing. “We are capable of following procedures, but for now we do not have statistical tools which make it possible to guarantee the control of the data processing”, explains the scientist. “We would like to develop a more efficient control strategy in terms of information processing, capable of defining thresholds and alerts in order to correct the deviations observed in a process”.

Handheld analyzers for field analysis

Eric Ziemons and his team also plan to concentrate their efforts on portable vibrational spectroscopy systems. “These are being actively developed and greatly interest the different actors in the pharmaceutical sector in the context of field analysis”, explains the specialist. “They make it possible to carry out first line analyses and therefore to more easily choose other more thorough analysis methods”. More specifically, the first priority of the Analytical Chemistry Laboratory is to improve the processing of the data collected and thereafter the portable systems with a view to more effectively combatting the counterfeiting of medicines (see article: ).

(1) Chavez PF, Lebrun P, Sacré PY, De Bleye C, Netchacovitch L, Cuypers S, Mantanus J, Motte H, Schubert M, Evrard B, Hubert P, Ziemons E. Optimization of a Pharmaceutical Tablet Formulation based on a Design Space Approach and using Vibrational Spectroscopy as PAT Tool. Int J Pharm., 486, 2015, 13-20. doi: 10.1016/j.ijpharm.2015.03.025.
(2) Chavez PF, Sacré PY, De Bleye C, Netchacovitch, Mantanus J, Motte H, Schubert M, Hubert P, Ziemons E, Active Content Determination of Pharmaceutical Tablets using Near Infrared Spectroscopy as Process Analytical Technology Tool, Talanta 144, 2015, 1352-1359. doi :10.1016/j.talanta.2015.08.018