Development and validation of zero and first-order derivative area under curve spectrophotometric methods for the...

The aim of this work is to establish two simple, economical, and rapid spectrophotometric methods for the quantification of entacapone in bulk material and in tablets. Further, this study is designed to validate the developed methods as per ICH guidelines.

In Methods I and II, a stock standard solution was prepared by dissolving 10 mg of entacapone in 100 mL of 10% v/v acetonitrile to obtain a concentration of 100 μg/mL. After suitable dilution, 10 μg/mL of entacapone was prepared and scanned in the UV-visible range 500-200 nm; entacapone showed a maximum absorbance at 384.40 nm. In Method I, area under curve (AUC) of the zero-order spectrum was recorded between 348.00 and 410.20 nm. While, in Method II, zero-order spectra were derivatized into first-order, and the AUC was recorded between 386.40 and 460.20 nm. For a linearity study, series of dilutions were prepared from stock solutions.

In Method I, and II, entacapone followed linearity in the concentration range of 2-12 μg/mL and 5-30 μg/mL with (r(2)>0.999). The amounts of entacapone estimated by both these methods were found to be 99.24 ± 0.054 and 98.68 ± 1.04, respectively.

The developed methods are simple, precise, rugged, robust, and economical. Both these methods can be used for routine analysis of entacapone from its tablet formulation.