Detection of counterfeit Viagra with Raman spectroscopy.

During the last few years, counterfeiters have become increasingly sophisticated by falsifying drugs and making them look identical to genuine tablets. In this paper, Raman spectroscopy is proposed as a fast and reliable method for the detection of counterfeit Viagra tablets. This technique can easily differentiate genuine from counterfeit tablets without the need of sample preparation. In total 18 tablets were analysed which all contained the active ingredient sildenafil, but different excipients were used, as could be observed in the Raman spectra between 1150 and 700 cm(-1). So, the spectra could be divided into genuine or counterfeit. Additionally, principal component analysis (PCA), combined with hierarchical cluster analysis (HCA), was used to establish an automated approach for the discrimination of counterfeit from genuine Viagra tablets. Raman spectroscopy, combined with principal components analysis, could be used in the future by customs or in the field to identify counterfeit tablets on the spot without involvement of trained chemists.