Determination of counterfeit medicines by Raman spectroscopy: Systematic study based on a large set of model tablets

In the last decade, counterfeit pharmaceutical products have become a widespread issue for public health. Raman spectroscopy which is easy, non-destructive and information-rich is particularly suitable as screening method for fast characterization of chemicals and pharmaceuticals. Combined with chemometric techniques, it provides a powerful tool for the analysis and determination of counterfeit medicines. Here, for the first time, a systematic study of the benefits and limitations of Raman spectroscopy for the analysis of pharmaceutical samples on a large set of model tablets, varying with respect to chemical and physical properties, was performed. To discriminate between the different mixtures, a combination of dispersive Raman spectroscopy performing in backscattering mode and principal component analysis was used. The discrimination between samples with different coatings, a varying amount of active pharmaceutical ingredients and a diversity of excipients were possible. However, it was not possible to distinguish between variations of the press power, mixing quality and granulation. As a showcase, the change in Raman signals of commercial acetylsalicylic acid effervescent tablets due to five different storage conditions was monitored. It was possible to detect early small chemical changes caused by inappropriate storage conditions. These results demonstrate that Raman spectroscopy combined with multivariate data analysis provides a powerful methodology for the fast and easy characterization of genuine and counterfeit medicines.