Spectrophotometric Determination of Mefenamic Acid in Pharmaceutical Preparations

Abstract

Three simple, rapid and accurate spectrophotometric methods were developed for the determination of mefenamic acid. The first method (Method I) is based on the reaction of mefenamic acid as N-donor with p-chloranilic acid as a π-acceptor. A red colour product shows peak at 520 nm and its absorbance is linear with concentration over the range 10-300 μg/mL with correlation coefficient (n = 12) of 0.9997. The second method (method II) involves oxidation of mefenamic acid with N-bromosuccinamide. A yellow colour product shows peak at 362 nm and its absorbance is linear with concentration over the range 5-70 μg/mL with correlation coefficient (n = 8) of 0.9999. The third method (method III) is based on the formation of an oxidative coupling product by the reaction of mefenamic acid with 3-methylbenzo-thiazolin-2-one hydrazone as a chromogenic reagent in presence of ferric chloride solution. A green colour product shows peak at 602 nm and its absorbance is linear with concentration over the range 1-6 μg/mL with correlation coefficient (n = 6) of 0.9999. The different parameters affecting the reaction pathway were thoroughly studied and optimized. The developed methods could be successfully applied to the determination of mefenamic acid in either pure form and in pharmaceutical formulations. The results obtained were in good agreement with those obtained using official methods.