ABSTRACT:
Two simple, rapid and sensitive spectrophotometric methods have been developed for the determination of Sildenafil Citrate (SIL) in pure form and pharmaceutical formulations. The spectrophotometric methods are based on the formation of binary complexes (ion-pair complexes)in dichloromethane (DCM) medium between the drug and tow acidic sulfonephthalein dyes, bromocresol purple (BCP)(method A) and bromophenol blue (BPB) (method B) with absorption maxima at 404 and 410 nm, respectively. The effects of analytical parameters on the reported systems were investigated. The complexation reactions were extremely rapid at room temperature and t¬he absorption values remain unchanged up to 24h. Beer’s law was obeyed in the concentration ranges of 0.6 - 20 and 0.8 -48 µg/ml, detection limits were 0.097 and 0.105µg/ml and the molar absorptivity coefficients were 2.77×104 and 2.60 ×104 L .moL-1.cm-1for BCP and BPB respectively. The proposed methods were successfully applied to the analysis of commercial tablets containing the drugs. Two methods were free-extractive, rapid, and have high sensitivity compared with other previous direct spectrophotometric methods. Interferences of the other ingredients and excipients were not observed.