Molybdate assisted ninhydrin based spectrophotometric method for the estimation of Metformin hydrochloride in bulk drugs and tablet dosage form

This paper describes an accurate, precise and economical spectrophotometric method for the determination of Metformin hydrochloride in bulk drugs and tablet dosage form. The analysis is based on the reaction of Metformin hydrochloride (primary amino group) reacts with ninhydrin and ammonium molybdate mixture to give Ruhemann's purple product with maximum absorbance (lambda(max)) at 570 nm. The effects of variables such as temperature, heating time, concentration of colour producing reagent and stability of colour were investigated to optimize the procedure. This reaction proceeds quantitatively at 90 +/- 1 degrees C in 10 min. Beer-Lambert's law is obeyed in the concentration range of 10-30 mu g/ml and is described by the regression equation Y = 0.061x - 0.125 with a regression coefficient (r(2)) = 0.997 (n = 5). For Metformin hydrochloride, the value of molar absorptivity and Sandell's sensitivity are 9.490 x 10(3) L/mol/cm and 0.0174 mu g/cm(2), respectively and of LOD and LOQ are found to be 1.6373 and 4.9616 mu g/ml, respectively. The statistically validated results indicate that the proposed method has good sensitivity, accuracy, precision and stability. The method is eco-friendly and economic as it does not involve any organic solvents. The developed method was successfully applied for the determination of Metformin hydrochloride in bulk powder and tablet dosage form.