Selectivity of identification of compounds from the group of phosphodiesterase-5 inhibitors (PDE-5i) in falsified products from the Polish market using attenuated total reflectance Fourier transform infrared spectroscopy and X-ray powder diffraction.

• Strategy for the screening analysis of falsified samples was developed. • ATR proved to be appropriate technique for PDE-5i identification in complex matrix. • Complementarity between ATR-FTIR and XRPD was demonstrated. • Developed strategy was successfully introduced into routine analysis. Falsified drugs are a growing problem and a great threat all over the world. Searching for easy, fast, not expensive and reproducible methods for identification of active pharmaceutical ingredients (APIs) is an important issue. The application of ATR-IR technique for identification of phosphodiesterase-5 inhibitors (PDE-5i) in falsified products from the Polish market has been demonstrated. Furthermore, the strategy of confirmation of the product's originality in a quick and easy way has been developed. The advantages of this application are: exceptional simplicity, very short measurement time, high selectivity in relation to structurally similar substances and almost no sample preparation. After validation, developed strategy has been successfully introduced into routine analysis. [ABSTRACT FROM AUTHOR]