This work presents a simple, fast and low-cost method for determining sildenafil citrate (SC) in Viagra® and in similar, generic and manipulated pharmaceutical formulations using flow injection analysis (FIA) with multiple pulse amperometric detection. The method consists on the application of three sequential potential pulses as a function of time. SC is detected at 1.6 and 1.9 V by two different irreversible oxidation processes. The third potential pulse (1.0 V) is applied for the regeneration (cleaning) of the surface of the boron-doped electrode. The limit of detection on an order of 10 nmol L-1 was reached with a relative standard deviation of less than 0.2% (n = 10) for 4.5 X 10-5 mol L-1 CS. The analytical frequency was calculated in 86 injections per hour. The addition recovery studies in all the samples were approximately 100% and the results were validated by chromatographic methods.
sildenafil citrate; multiple pulse amperometry; flow injection analysis
