Spectroscopic Characterization and Quantitative Estimation of Ropinirole Hydrochloride Through Charge Transfer Complex Formation and Redox Reaction

Abstract

Two spectrophotometric methods for the estimation of ropinirole hydrochloride (RP) in bulk drug and in its tablet formulations are described. Method A based on charge transfer (CT) interactions between RP as amino heterocyclic donor and chloranilic acid (CLA) as π-acceptor showing absorption maximum at 528 nm. Factors controlling the CT-reactions were studied, optimized and composition of the formed CT-complexes was identified. Job’s method of continuous variation was used to detect the stoichiometric ratios of the formed complexes and they showed that 1:1 complexes were produced between RP and CLA. Also the solid CT-complexes were characterized by FTIR spectroscopy where the formed complexes included proton and electron transfer. The method B is based on the formation of blue colored chromogen due to the reaction of RP with Folin Ciocalteu (FC) reagent in presence of alkali which exhibits an absorption maximum at 633 nm. Beer’s law range is 1–100 μg /ml and 5–40 μg /ml for methodA and method B respectively. Under the optimum conditions, linear relationships with good correlation coefficients were identified with high accuracy and precision. The proposed methods were successfully applied to the determination of RP in formulations.