Rapid Resolution RP-HPLC-DAD Method for Simultaneous Determination of Sildenafil, Vardenafil, and Tadalafil in Pharmaceutical Preparations and Counterfeit Drugs

Abstract

A novel and Rapid Resolution Reversed-Phase High-Performance Liquid Chromatography-Diode Array Detector method has been developed and validated for the simultaneous determination of sildenafil, vardenafil, and tadalafil in pharmaceutical preparations and counterfeit drugs. An Agilent Zorbax SB C8 column (50 × 4.6 mm i.d., 1.8 μm particle size) was used. The mobile phase consisted of a mixture of 0.030 M of ammonium formate (adjusted to pH 3.0 with formic acid) and acetonitrile in the ratio 70:30. Ultraviolet (UV) detection was performed at 230 nm. Total run time was 7 min; these three drugs were eluted at the retention times of 1.654, 2.032, and 5.067 min for vardenafil, sildenafil, and tadalafil, respectively. The method was validated for accuracy, precision, linearity, specificity, and sensitivity. From the validation study, it was found that the method is specific, rapid, accurate, precise, and reproducible. Calibration curves were linear over the concentration ranges of 0.2–200 μg ml−1 for sildenafil, vardenafil, and tadalafil. The limits of detection (LOD) values were 1.0, 1.1, and 1.0 ng and the limit of quantification (LOQ) values were 2.0, 2.1, and 2.0 ng for sildenafil, vardenafil, and tadalafil, respectively. The method is rapid both for routine quantitative analysis of sildenafil, vardenafil, and tadalafil in pharmaceutical preparations and screening their suspected counterfeit drugs.