Development and validation of kinetic spectrophotometric method for the determination of metoprolol tartrate in pharmaceutical preparations

A simple and sensitive kinetic spectrophotometric method for the determination of metoprolol tartrate has been proposed. In the developed approach analyte reacts with ninhydrin in N,N'-dimethylformamide (DNIF) medium at 95 +/- 1 degrees C to produce blue colour. Determination was based on the measurement of absorbance at 595 nm as a function of time. In the initial rate and the fixed time (10 min) procedures linear dependencies between the measured signal (reaction rate or absorbance) and the analyte concentration were observed in the range 10.0-60.0 mu g mL(-1) of metoprolol tartrate. The obtained linear plots were described by the following regression equations: log(rate) = 3.009 + 0.9983 logC, and A = 3.30 x 10(-4) + 1.15 x 10(-2) C, respectively. The corresponding limits of detection and quantitation for the initial rate and the fixed time methods were: 8.40 x 10(-3) and 2.55 x 10(-2) mu g mL(-1), and 0.227 and 0.686 mu g mL(-1), respectively. The results obtained in both procedures were precise and reproducible. Recovery was 99.99-100.16%. Relative standard deviation did not exceed 0.65%.