Development of an aqueous kinetic spectrophotometric method for the analysis of lacosamide optimized through Taguchi and Box-Behnken design; A comparative green assessment

• Oxidation based green analytical method is developed for quantitation. • Using water as the solvent is a green approach for method development. • Green analytical tools ensure the eco-friendliness of developed method. • Optimization and comparison of the developed method by Box-Behnken and Taguchi design. • Pharmaceutical formulations and pure forms of an antiepileptic medication (lacosamide) is quantified using kinetic spectrophotometry. A green and sustainable redox reaction for the quantitative determination of lacosamide is developed using kinetic spectrophotometry. The method development involves the reaction between lacosamide and an aqueous solution of alkaline KMnO 4 , which form a product of a bluish-green colour at room temperature that was studied on a UV–visible spectrophotometer at 610 nm. Various factors influence the colour's development and its stability. The Box-Behnken design was used to optimize the reaction conditions as well as to achieve the desirability function (drug concentration 42 µg mL −1 , KMnO 4 concentration 163 µg mL −1 at 1443.8 s) to record the maximum absorbance. The Box Behnken Design method was compared with the Taguchi method (drug concentration = 60 µg mL −1 , KMnO 4 concentration = 200 µg mL −1 at 1050 s), and a similar absorbance was obtained along with a comparable S/N ratio with significant controlling factors. The initial rate, fixed time, fixed absorbance, order of reaction and rate constant methods were studied but the fixed time and initial rate of reaction methods were found more appropriate. The calibration plot is linear from 5 µg mL −1 to 60 µg mL −1 with a correlation coefficient value of 0.9994. Detection limit (LOD) and quantification limit (LOQ) were found 1.31 µg mL −1 and 3.9 µg mL −1 , respectively. Using AGREE and analytical eco-scale tools the developed method's greenness was evaluated according to its guidelines and found to be up to the par. The applicability of the proposed green analytical method is used to determine lacosamide in its formulations.