Chemical Profile of Sildenafil and Related Compounds
Japanese Journal of Forensic Science and Technology
Sildenaˆl and related compounds, vardenaˆl, tadalaˆl and hydroxyhomosildenaˆl, in dietary supplements were characterized using thin layer chromatography (TLC), infrared (IR) spectroscopy, gas chromatography/mass spectrometry (GC/MS), high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS). TLC with DragendorŠ reagent gave a lower detection limit than 1 mg for all 4 compounds. IR spectra of the compounds were so characteristic as to discriminate one from
... scriminate one from another easily. After TMS derivatization, all the peaks of these compounds appeared and well-separated on the GC/MS chromatograms at a high column temperature (320°C), although hydroxyhomosildenaˆl was not detected without derivatization. In HPLC and LC/ MS analyses, an ODS column with a mobile phase composed of a mixture of 20 mM ammonium acetate (pH 5.0) and methanol (4060) allowed separation of the 4 compounds. Simple electrospray-ionization mass spectra with only protonated molecules were obtained except for tadalaˆl, which was cleaved easier than the other compounds, so cone voltage should be lower for tadalaˆl. Quantitative analysis of the 4 compounds was carried out using HPLC (UV at 230 nm). The lower limit of detection for each compound was 50 ng/ml at a 10-ml injection volume (0.5 ng on the column, S/N>3). A calibration curve was linear in the range of 0.01 1.0 mg/ml for each compound (r 2 >0.997). Our methods were applied to casework samples (conˆscated tablets), and disclosed that those tablets contained varying amounts of sildenaˆl and/or tadalaˆl and were counterfeit products.