Development and Validation of Ratio Derivative Spectrophotometric Method for Estimation of Metronidazole Benzoate and Related Impurity in Bulk and Pharmaceutical Formulation

A simple, accurate and precise spectroscopic method was developed for simultaneous estimation of Metronidazole Benzoate and related impurity in bulk and pharmaceutical formulation by ratio derivative simultaneous equation method. The method is based on dividing the spectrum for a mixture into the standard spectra for each of the analysis and to obtain a spectrum that is independent of the analyte concentration used as a divisor. In this method for MND, MNI and BA the linearity range 2.0-10 μg/ml were divided by the divisor 2.0 μg/ml of MTZ. The use of standardized spectra as divisors minimizes experimental errors. Ratio spectra derivative permits the use of the wavelengths corresponding to maximum or minimum and also the use of the distance between consecutive maximum and minimum. For that the divided spectra was converted to second derivative using DL value 16 and SF value 100. The Metronidazole shows max absorbance at 270.00 nm, 2- Methyl-5Nitroimidazole show max absorbance at 257.42 nm and Benzoic Acid shows max. absorbance at 245.61 nm. The method was found to be linear (r2>0.997) in the range of 2.0-10 μg/ml. The limit of determination was 0.049 μg/ml and 0.026 μg/ml and0.038 μg/ml for Metronidazole, 2-Methyl-5-Nitroimidazole and Benzoic Acid, respectively. The limit of quantification was 0.150 μg/ml and 0.079 μg/ml and 0.115 μg/ml for Metronidazole, 2-Methyl-5-Nitroimidazole and Benzoic Acid, respectively. The accuracy of this method was evaluated by recovery studies and good recovery result was obtained 100%. The method was successfully applied for simultaneous determination of Metronidazole, 2-Methyl-5-Nitroimidazole and Benzoic Acid.