Comparison and combination of spectroscopic techniques for the detection of 1 counterfeit medicines

14 During this study, Fourier transform infrared spectroscopy (FT-IR), near infrared 15 spectroscopy (NIR) and Raman spectroscopy were applied to 55 samples of counterfeit and 16 imitations of Viagra ® and 39 samples of counterfeit and imitations of Cialis ® . The aim of the 17 study was to investigate which of these techniques and associations of them were the best for 18 discriminating genuine from counterfeit and imitation samples. Only the regions between 19 1800-400 cm -1 and 7000-4000 cm -1 were used for FT-IR and NIR spectroscopy respectively. 20 Partial Least Square analysis has been used to allow the detection of counterfeit and imitation 21 tablets. It is shown that for the Viagra ® samples, the best results were provided by a 22 combination of FT-IR and NIR spectroscopy. On the other hand, the best results for the 23 Cialis ® samples were provided by the combination of NIR and Raman spectroscopy (140024 1190 cm -1 ). These techniques permitted a clear discrimination between genuine and 25 counterfeit or imitation samples but also the distinction of clusters among illegal samples. 26 This might be interesting for forensic investigations by authorities. 27