Developing a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous determination of phosphodiesterase-5 inhibitors in health supplements in Vietnam

Sildenafil, tadalafil, vardenafil, sulfoaildenafil, amino tadalafil, N-desmethyl tadalafil are phosphodiesterase type-5 (PDE-5) inhibitors that have been frequently detected as adulterants in sexual enhancement supplements. They are prohibited under Circular No.10/2021/TT-BYT of the Ministry of Health of VietNam, dated June 30, 2021. This study aimed to develop and to apply a liquid chromatography-tandem mass spectrometry (LC-MS/MS) procedure to simultaneously determine these substances in health supplements. The study was performed using a simulated sample containing analytes, herbals and excipients. Chromatographic and MS parameters were optimized through investigation. The analytical method was developed using LC-MS/MS with electrospray ionization positive (ESI+) mode and validated in accordance with Association of Official Analytical Chemists (AOAC) regulations. The established method was then applied to determine the presence of adulterated PDE-5 inhibitors in health protection products obtained from the Vietnamese market. The developed analytical procedure featured the following settings: the column was InertSustain C18 (2.1×150 mm, 3 μm); mobile phase consists of 0.1% formic acid in water and 0.1% formic acid in acetonitrile; flow rate was maintained at 0.20 mL/min and analytes were eluted via a solvent gradient program. The analytical procedure met the requirements of AOAC. Analysis results from the health supplement samples revealed that 25% of the total samples collected were found to be adulterated with PDE-5 inhibitors (6 out of 24 collected samples). A LC-MS/MS procedure for simultaneously determining sildenafil, tadalafil, vardenafil, sulfoaildenafil, amino tadalafil, N-desmethyl tadalafil in health supplements was developed, validated, and applied.