Spectrofluorimetric determination of sildenafil: a new analytical alternative for its analysis

Abstract

In aqueous solutions, sildenafil presents a very low fluorescence emission and a limited linear range. In presence of a cationic surfactant hexadecyltrim ethylammonium bromide (HTAB, method A) and anionic surfactant sodium dodecyl sulfate (SDS, method B) a great fluorescence enhancement was observed and the linearity range was enlarged. These surfactants-drug interactions lead to the development of two sensitive methods for sildenafil spectrofluorimetric determination. Nature of interactions between sildenafil and surfactants were studied and different parameters which influence these associations were discussed. Sildenafil was quantitatively determined at an emission wavelength of 435 nm and 415 nm by method A and B respectively with detection limit of 0.0012 µg mL-1 and 0.0016 µg mL-1. The methods have been successfully applied to the analysis of bulk drug, tablets and herbal medicines.