Different Spectrophotometric Methods for Determination of Mefenamic Acid in Presence of its Two Toxic Impurities

Abstract

Two selective, accurate, precise and validated spectrophotometric methods were developed for determination of mefenamic acid (MEF) and its two toxic impurities, benzoic acid (BA) and 2, 3 dimethylaniline (DMA) without preliminary separation. The developed methods are direct spectrophotometric method {0D} {Method I}, area under the curve {AUC} {Method II}. In method {I} Mefenamic determine directly by measured absorbance at 350 nm in the range of 2-15 μg/mL. In method {II} the drug was determined by measuring AUC in the wavelength range of 330-370 nm while the impurities could be determined by dividing by of 10 μg/mL MEF then interference from MEF was eliminated by subtracting the amplitude of the constant at 350 nm and then multiplying by the divisor. Then by using AUC at the range 220-230 nm and 235245 nm and by applying in Cramer’s rule, concentrations of BA and DMA could be calculated. The work introduces a low cost and does not need sophisticated steps for determination of MEF, BA and DMA in their powders and in pharmaceutical preparations. The validation of methods was performed according to ICH guidelines regarding accuracy, precision and selectivity. No significance difference was found when these methods were compared to the reported one.