Development of a Micellar electrokinetic capillary chromatography method for the determination of three drugs employed in the erectile dysfunction therapy.

A Micellar electrokinetic capillary chromatography method is proposed for the determination of sildenafil, vardenafil and tadalafil, which are employed in oral therapy for erectile dysfunction. Optimum conditions for the separation were investigated. A background electrolyte solution consisting of 10 mM phosphate buffer adjusted to pH 12.0, sodium dodecyl sulfate (SDS) 25 mM, hydrodynamic injection, and 25 kV as separation voltage were used. Relative standard deviations (R.S.D.s) were 1.0, 1.0, 0.4% and 2.9, 2.9, 1.9% for migration time and corrected peak area (CPA) (n = 9) for sildenafil, vardenafil and tadalafil, respectively. Detection limits obtained for the three drugs ranged from 0.19 to 0.61 mg L(-1). A linear concentration range between 1 and 20 mg L(-1) was obtained. A ruggedness test of this method was checked using the fractional factorial model of Plackett-Burman, in which the influence of six factors at three different levels was tested on different electrophoretic results: resolution and corrected peak area. The statistical evaluation of the electrophoretic results was achieved by Youden and Steiner method. The described method is rapid, sensitive and rugged and it was tested in the pharmaceutical formulations analysis obtaining recoveries between 98 and 107% respect to the nominal content.