DEVELOPMENT AND VALIDATION OF SPECTROPHOTOMETRIC METHODS FOR SIMULTANEOUS ESTIMATION OF METOPROLOL SUCCINATE AND TELMISARTAN IN COMBINED PHARMACEUTICAL FORMULATION

Four simple, rapid, precise, economical and accurate spectrophotometric methods have been developed for simultaneous analysis of Metoprolol succinate and Telmisartan in their combined dosage form. Method 1, First derivative simultaneous equation method (Vierodt’s method). It employs formation and solving of simultaneous equation using two wavelengths 230.2 nm (λmax of Metoprolol succinate) and 237 nm (λmax of Telmisartan) in first derivative spectra. Method 2, First derivative Q-Absorbance equation method. It involves, formation of Q-absorbance equation at 231.8 nm (isoabsorptive point) and 237 nm (λmax of Telmisartan) in first derivative spectra. Method 3, Absorbance correction method, involves measurement of absorbance at 296.6 nm for estimation of TEL and measurement of corrected absorbance at 223 nm for estimation of MET. Method 4, Combination of  First derivative dual wavelength ,which uses the difference in absorbance at 282.4 nm and 284.6 nm for estimation of MET and zero crossing first derivative spectrophotometry involves measurement of amplitudes at 330 nm for estimation of TEL in first derivative spectra. Developed methods were validated according to ICH guidelines. The calibration graph follows Beer’s law in the range of 3-20 µg/ml for MET and 4-16 µg/ml for TEL with R square value greater than 0.999. Accuracy of all methods was determined by recovery studies and showed % recovery between 99 to 101%. Intraday and interday precision was checked for all methods and mean %RSD was found to be less than 2 for all the methods. The methods were successfully applied for estimation of MET and TEL in marketed formulation.