Verification of the authenticity of drugs by means of NMR relaxometry—Viagra® as an example

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1H spin-lattice Nuclear Magnetic Resonance (NMR) relaxometry, vibrational spectroscopy and Atomic Force Microscopy (AFM) have been applied to differentiate between original and counterfeit Viagra®. The relaxation studies have been performed in a frequency range covering four orders of magnitude, from 4 kHz to 40 MHz. It has been shown that for the counterfeit product the relaxation is bi-exponential in the whole frequency range, while for the original Viagra® the relaxation process is always single exponential. Thus, even a qualitative analysis of the relaxation data makes it possible to identify the falsified medicine. Moreover, it has been demonstrated that vibrational spectroscopy does not allow for differentiating between the products, while AFM studies are likely to lead one to deceptive conclusions regarding the originality of the medicine. Furthermore, a quantitative analysis of the relaxation data has been performed to describe in detail the relaxation properties of the original and falsified products.

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