Determination of Captopril by Using Phosphorus Molybdenum Blue as Spectral Probe Reagent

A novel method was established to determine captopril content by using phosphorus molybdenum blue as spectral probe reagent The experiment indicated that PO43- reacted with [Mo7O24](6-) in 0.30 mol/L H2SO4 solution to form a product of phosphorus molybdenum heteropoly acid ([H2PMo12O)(40)](-)) which was reduced to phosphorus molybdenum blue (H3PO4 center dot 10MoO(3)center dot Mo2O5) by captopril. The absorbance Of phosphorus molybdenum blue was measured at the maximum absorption wavelength 730 nm and the amount of Captopril could be determined based on this absorbance. A good linear relationship between absorbency and the concentration of captopril was in the range of 4.0-100.0 mu g/ml and the regression equation was A = -0.01336 + 0.00504c (mu g/mL) with a correlation coefficient 0.9992. The method had been successfully applied to the determination of captopril in pharmaceutical samples which the average recovery rate was in the range of 98.6-101 %.