Analysis of undeclared synthetic phosphodiesterase-5 inhibitors in dietary supplements and herbal matrices by LC-ESI-MS and LC-UV.

A liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) method was developed to screen for the presence of synthetic phosphodiesterase type 5 (PDE-5) inhibitors including sildenafil, tadalafil and vardenafil. The method was applied to the analysis of dietary supplements and bulk herbal materials. Bulk powders or composites of tablets, capsules or liquids were prepared and an extraction of PDE-5 inhibitors was performed using a mixture of acetonitrile and water with sonication. Identification of sildenafil, vardenafil or tadalafil was accomplished using a single quadrupole mass spectrometer coupled to a liquid chromatograph with an electrospray interface. Positive ion detection in the full scan mode was used while in-source collision induced dissociation (CID) provided several structurally significant fragment ions to aid in the mass spectral identification. Approximately half of the 40 botanical products analyzed were found to contain undeclared synthetic PDE-5 inhibitors. For products found to contain one of these three compounds by LC-MS, HPLC with UV detection was used for quantitation.