Development of a Robust Method for Screening PDE-5 Inhibitor Additives in Dietary Supplements Using UPLC-MS/MS

A novel ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) method was developed to detect the illegal additive of phosphodiesterase type 5 (PDE-5) inhibitors in dietary supplements. With the optimized chromatographic program, vardenafil, sildenafil, and tadalafil were separated within 5 minutes. The MS1, MS2, and retention time of PDE-5 inhibitors were acquired simultaneously within the information dependent acquisition mass spectrometry mode. Quantification was achieved via the quantity ion current chromatogram that was extracted from the total ion current. The linear range of vardenafil and sildenafil was 0.5-48 mg/L while the range of tadalafil was 0.3-36 mg/L. The correlation coefficients of the calibration curves of three PDE-5 inhibitors were all greater than 99.9%. At three concentration levels, the RSD values of the five repeat tests were all better than 1.30%. Sildenafil was detected in one dietary supplement. The comprehensive method of this study is reliable and may be a powerful tool for routine PDE-5 inhibitor screening and determination.