“…In this regard, various spectrometric and chromatographic methods have been adopted to analyze the illegally added drugs in complex matrices [ 3 , 4 , 5 , 9 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. High-performance liquid chromatography with diode array detection (HPLC–DAD) and liquid chromatography with mass spectrometry (LC–MS) have been previously used to detect PDE-5 inhibitors and their analogs [ 3 , 5 , 7 , 8 , 9 , 10 , 16 , 17 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. When the standards of PDE-5 inhibitors and their analogs are available, HPLC with a UV spectrometer is a simple method for quantitative analysis [ 11 ].…”