A novel technique for the determination of propylthiouracil with sodium nitroprusside as a chromogenic reagent by spectrophotometry

A new method for the determination of propylthiouracil by spectrophotometry using sodium nitroprusside as a chromogenic reagent is described. The experiment indicated that a turquoise product could be formed by the reaction between propylthiouracil and sodium nitroprusside in basic solution. The mole ratio of propylthiouracil and sodium nitroprusside in the product is 1 : 3. The maximal absorption wavelength (λmax) of the product is 680 nm, the molar absorption coefficient (ɛ680) 1.20 × 103 L/(mol cm). Lambert-Beer’s law is obeyed in the range of 0.5–55.0 μg/mL. The linear regression equation is A = 0.00479 + 0.00705c (μg/mL), with a correlation coefficient of 0.9991. The recoveries are obtained from 96.6 to 102.3%. The proposed method was successfully applied to determine propylthiouracil in pharmaceutical samples with satisfactory results.