Spectrophotometric Determination of an Antidiabetic Drug Metformin by KMnO4 and Sulphanilic Acid Method

Abstract

For the determination of Metformin, two simple and sensitive spectrophotometric methods are developed. The first method A is indirect; after allowing the reaction between KMnO4 and drug, the excess amount of KMnO4 is determined spectrophotometrically. The excess of KMnO4 was made to react with a fixed amount of methyl orange dye and the absorbance is measured at 510nm. For this method, Beer’s law is obeyed in the concentration range of 0.5- 5 μg/ml. Molar absorptivity and Sandell’s sensitivity are found to be 0.12916 x 105 L mol-1cm-1 and 0.01 μg/cm2 respectively. The second method B is based on the principle of formation of orange color as a result of reaction between drug and diazotised sulfanilic acid. The resulting solution is estimated spectrophotometrically by taking absorbance at 510 nm. Conditions of the methods are optimized by studying all the parameters that affect the stability and colour of the complex. For this method, Beer’s law is obeyed in the concentration range 1.0 - 8.0 μg /ml. Molar absorptivity and Sandell’s sensitivity are found to be 0.2583 x 104 L mol-1cm-1 and 0.05 μg/cm2 respectively. The proposed methods are appropriate for determination of metformin in pharmaceutical formulations.