title: Extractive spectrophotometric methods for the assay of sildenafil citrate (Viagra) in pure form and in pharmaceutical formulations.
abstract: Two simple and sensitive extractive spectrophotometric methods for the determination of sildenafil citrate (SC) are proposed. The methods are based on the formation of ion-association complexes of sildenafil citrate with bromocresol green (BCG, method A) and with chromoxane cyanine R (CCR, method B) in aqueous acidic buffer. The complex species, extractable to chloroform phase, were quantitatively measured at 415 and 460 nm for methods A and B, respectively. Beer's law was obeyed in the SC concentration range 1.25-25 mug ml(-1) with a limit of detection 0.16 mug ml(-1) and 1.5-60 mug ml(-1) with a limit of detection 0.18 mug ml(-1), respectively, for methods A and B. The methods have been successfully applied to the analysis of bulk drug and its tablets. No interference was observed from common pharmaceutical adjuvants.
authors.affiliation: Department of Studies in Chemistry, University of Mysore, Manasagangothri, Mysore 570006, India.
authors.forename: N D
authors.initials: ND
authors.lastname: Dinesh
authors.forename: P
authors.initials: P
authors.lastname: Nagaraja
authors.forename: N M
authors.initials: NM
authors.lastname: Made Gowda
authors.forename: K S
authors.initials: KS
authors.lastname: Rangappa