Azo Coupling Reaction for indirect Spectrophotometric Determination of Furosemide using Resorcinol as a Reagent

A simple and accurate method to determinate furosemide (FUR) based on converting the secondary amine to primary amine with acidic hydrolysis then azotization by nitrous acid and coupled with resorcinol as a coupling agent in aqueous medium at pH 13. The optical characteristic like beers law limit found to be (0.25-2.5) μg.ml⁻¹, detection and quantification limits (0.0196) (0.0654) μg.ml⁻¹respectivly and Sandel sensitivity was 0.006738 μg.cm⁻². The least-square method was used to evaluate the regression equation and the correlation coefficient. The resulted azo dye has a maximum absorbance at 430 nm with light orange color. The developed method was successfully applied to determinate FUR in its formulation with 84-105 % as a recovery with a relative standard deviation not more 2% and less than 5% relative error. To validate the proposed method, the standard addition method was applied to evaluate FUR in different formulation sources.