Spectrophotometric Determination of Mefenamic acid in pure and Pharmaceutical Preparations

Abstract

Chromate ions CrO4-2 have been used in three simples, rapid, an accurate spectrophotometric method. These methods were suggested to estimate mefenamic acid in its pure form and pharmaceutical preparations. These methods were different from each other with reactants components, and they are similar as, indirect methods and depends on oxidation-reduction reaction. So that, Method 1, based on oxidation reduction reaction between mefenamic acid and chromate ion in presence of acidic medium and sodium oxalate to form a water soluble, and stable pinkish-violet colored complex with 1,5-diphenylcarbazide as a reagent which was measured at λmax 545 nm. Method 2 depends on oxidizing mefenamic acid with chromate ions in presence of sodium oxalate as a catalyst agent and acidic medium to form with indigo carmine λmax at 610 nm. water soluble and stable blue complex. Finally, method 3 based on the reaction between mefenamic acid and chromate ion in presence of sodium oxalate and acidic medium to form with chrome azurol S a red complex measured λmax at 512 nm. These three methods have been followed Beer's law at (2-40,1.2-40 and 2-36) μg/mL methods 1,2 and 3 respectively, while molar absorptivity and Sandall's sensitivity 0.84×104, 0.54×104 and 1.08×104 1.mol-1.cm-1 and 0.0287, 0.0446 and 0.0223 μg.cm-2 for methods 1,2 and 3 respectively. The suggested methods were applied successfully to determination of mefenamic acid in pharmaceutical formulation with good recoveries.