Development of the Spectrophotometric Method for the Determination of Metoprolol in Tablets by using Bromothymol Blue

A simple, eco-friendly, rapid, and economic spectrophotometric method for the determination of metoprolol tartrate in tablets has been developed. The procedure for metoprolol determination is based on a reaction with bromothymol blue (BTB) in acetonitrile medium. The maximum formation of the colored product was observed in acetonitrile at the absorption maximum at a wavelength of 402 nm. The stoichiometry of molecular complexes was determined by Job's method and it was found to be 1 to 1. The optimal concentration of BTB was 1.6·10-4 M. The linear relationship between absorbance at λmax and concentration of analyte ranging 16.00-24.00 μg mL-1 was found. Regression analysis of Beer’s law plot at 402 nm yielded the regression equation, y = 0.0199x + 0.0721. High values of correlations coefficient R2 = 0.9990 and small values of intercept validated the linearity of calibration curve and obedience to Beer’s law. The calculated LOD and LOQ values were 1.90 and 5.78 μg mL-1, respectively. The proposed green spectrophotometric method is simple, rapid, and suitable for routine pharmaceutical analysis.