SPECTROPHOTOMETRIC DETERMINATION OF SOME PHARMACEUTICAL PIPERAZINE DERIVATIVES THROUGH CHARGE-TRANSFER AND ION-PAIR COMPLEXATION REACTIONS

Simple and sensitive spectrophotometric methods are described for the assay of three piperazine derivatives; ketoconazole, piribedil and pra zosin hydrochloride based on charge-transfer and ion-pair complexation reactions. The first method is based on the reaction of the basic dru g with 2,3,-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in acetonitrile. The orange-red colour formed due to the formation of charge-transfer complex showed maximum absorbance at 460 nm. The second method is base d upon the interaction of the basic drug in dry chloroform with bromop henol blue (BPB) in the same solvent to produce a stable yellow ion-pa ir complex which absorbs at 410 nm. Beer's law was obeyed for both met hods and the relative standard deviations were found to be less than 1 %. The two methods can be applied to the analysis of tablets, with no evidence of interference from excipients. A more detailed investigatio n of the complex was made with respect to its composition, association constant and free energy change. (C) 1997 Elsevier Science B.V.