The optimum analytical conditions included electrolyte solution of 20 mM arginine (Arg) / acid acetic (Ace) / acetonitrile (ACN) 20% pH 6.5, silica capillary 50 μm inner diameter with effective length of 50 cm, separation voltage of 20kV, siphoning hydrodynamic injection at a height of 25 cm for 30 s. At the optimum analytical conditions, the limits of detection of acetyl vardenafil, homosildenafil, hydroxy acetildenafil, and mirodenafil were 2.1, 1.6, 2.3, and 1.3 mg / L, respectively.