P-dimethyl amino benzaldehyde as a new chromogenic reagent for the determination of nonsteroidal anti-inflammatory drug by first-order derivative spectrophotometry

Mefenamic acid reacts with P-dimethylamino benzaldehyde to give a bluish-green complex in acidic media after heating for 90 s at 90 degrees C, having maximum absorbance at 597.5 nm. The reaction is selective for mefenamic acid with 0.02 mg/10 mL as visual limit of quantitation and provides a basis for a new spectrophotometric determination. The reaction obeys Beer's Law from 0.02 mg to 2.5 mg/10 mL of mefenamic acid and the relative standard deviation is 0.50%. The quantitative assessment of tolerable amounts of other drugs not interfering has also been studied. First-order derivative spectrophotometric procedure was applied for the determination of mefenamic acid in pharmaceutical preparations.