Simultaneous Determination of Sildenafil, Tadalafil, and Vardenafil in Pharmaceutical Preparations by High-Temperature Gas Chromatography/Mass Spectrometry

Sildenafil (SD), tadalafil (TD), and vardenafil (VD) are drugs used to treat erectile dysfunction (ED). Pharmaceutical counterfeiting-related SD, TD, and VD compounds are becoming a critical problem due to their harmful side-effects. Especially, SD and TD are two major counterfeit ED drugs in South Korea. In this study, a new high-temperature gas chromatography/mass spectrometry (HTGC/MS) method was developed for the rapid determination of SD, TD, and VD in pharmaceutical preparations. A HT GC column was introduced for the rapid analysis of high molecular weight and high boiling point compounds. High-speed centrifugation led to shortened time for results. Calibration curves were linear (R (2) ae 0.9972) over the concentration ranges of 12.5-100 A mu g mg(-1) for TD and VD, and 25-175 A mu g mg(-1) for SD. The intra- and inter-day precisions were within 7.5 %, while the intra- and inter-day accuracies ranged from -3.0 to 8.0 %. The limits of quantification were 0.7 A mu g mg(-1) (SD and TD) and 0.13 A mu g mg(-1) (VD). The recoveries were in the range of 87.3-102.4 %. The developed method was rapid and accurate both for routine quantitative measurement of SD, TD, and VD in pharmaceutical preparations as well as screening their suspected counterfeit compounds.