Spectrophotometric and Conductimetric Determination of Dipyridamole in Pure and Dosage Forms Using Chromotrope 2B and Phosphotungstic Acid

A spectrophotometric method is proposed for determining dipyridamole in pure form and in pharmaceutical preparations. Chromotrope 2B was used as a charge-transfer complex forming agent with absorption maximum ≅ 40 nm red shifted relative to the chromotrope 2B itself. The variables affecting the formation of the C.T. complex were studied and optimized. Linear calibration graphs were obtained up to 60 μg ml^-1 at room temperature. The method was found to be accurate, precise and can be successfully used for authentic and pharmaceutical preparations in the working range up to 600 μg. A conductimetric method using phosphotungstic acid as ion-associate forming agent is proposed. The relative average error is 1-2%. Water-ethanol (1:2) mixture was used as solvent. Excellent recoveries and low standard deviations were obtained. Working ranges are 40-260 mg and 35-110 mg for pure dipyridamole and tablets, respectively.