development and validation of a derivative spectrophotometric method for simultaneous multicomponent determination of levodopa, carbidopa and entacapone

In this study entacapone, levodopa, and carbidopa, were determined with high precision in the presence of each other. uv-vis spectroscopy was used as an easy and low-cost technique for the analysis and the derivative spectrophotometric method was applied for elimination of absorption interferences. for this purpose, the derivative spectra of each compound were studied separately, and zero crossing points were determined for each of them. the zero-crossing points in which the absorption was observed only for one compound were found and evaluated for quantitative analysis. calibration curves were drawn from the second and third derivative signals for each compound and the linear range was determined. the method was linear in the range of 1-5 µg/ml for levodopa, 0.25-1.7 µg/ml for carbidopa, and 2-14 µg/ml for entacapone. the accuracy and precision of the proposed method were evaluated by within-day and between-day tests (cv < 1.56% and error < 1.7%) and finally, these drugs were determined in pharmaceutical dosage forms by the developed method.