Abstract
Capillary electrophoresis (CE) with diode-array detection has been used to develop a simple and rapid method for assay of vardenafil in the bulk drug and in a tablet formulation. Multi-response optimization of sensitivity, speed, repeatability of peak height and migration time, and their relative standard deviation (RSD; n = 5), was performed. Electrophoretic factors assumed to be independently affecting the analysis were optimized by use of factorial design and response-surface methods. Other factors were optimized by the univariant method. The optimum conditions were: running buffer 100 mm phosphate, pH 6, injection time 8 s, column temperature 25C, separating potential 25 W, column length 31.2 cm, and detection at 222 rim. The method was validated in the presence of the excipients identified by the manufacturer of the tablets (Levitra). Good analytical data were obtained, including linear range 0.5-75 mu g mL(-1), recovery 98.8%, repeatability (as RSD) 1.3% (seven consequent injections on the same day), intermediate precision (as RSD) 3.4% (five injections over a week), and limits of detection and quantification 0.042 and 0.140 mu g mL(-1), respectively. Selectivity was assessed in relation to the other, structurally related, drug commonly used to treat erectile dysfunction (sildenafil); sufficient separation was achieved.