Simultaneous determination of 38 phosphodiestrase-5 inhibitors in illicit erectile dysfunction products by liquid chromatography-electrospray ionization-tandem mass spectrometry

This paper describes the development and validation of simultaneous analytical method for 38 compounds, sildenafil, tadalafil, vardenafil and their analogues in illicit erectile dysfunction (ED) products by the liquid chromatography-electrospray ionization-tandem mass method (LC-ESI-MS/MS). Chromatographic separation was performed on a C18 reversed-phase column using a gradient of solvent A: aqueous 2 mM ammonium formate solution and solvent B: acetonitrile (ACN). All components were monitored under time-scheduled multiple reaction monitoring (MRM) mode. The limits of detection (LOD) ranged from 0.004 ng/ml to 0.455 ng/ml and the limits of quantification (LOQ) ranged from 0.012 ng/ml to 1.5 ng/ml. Calibration curves were linear with correlation coefficients over 0.9991. Mean recoveries ranged from 73.6% to 111.3%, and relative standard deviation (RSD) was less than 10%. The intra- and inter-day precision ranged from 0.2% to 16.3% and from 0.2% to 17.0%, respectively. The proposed method was applied to investigate the 52 illicit ED products.