Adaptation of Bromcresol Green Method for the Determination of Reserpine

A series of dyes were selected for experimentation as reagents for the colorimetric determination of reserpine. Among these, bromcresol green, scaret red sulfonate, bromthymol blue, bromcresol purple and orange Ⅱ when combined with reserpine at a certain pH (phosphate-citrate buffer), formed sensitive and stable colored addition products in chloroform solution. These have not hitherto been reported in the literature. The optimum conditions for the reaction of reserpine with bromcresol green have been studied in detail. A method which obeys Beer's law, is proposed giving a suitable concentration of reserpine, ranging from 2 to 23 mcg per ml of chloroform at pH 3±0.5.The extinction was measured colorimetrically 420 mμ against a reagent blank, and was shown to remain stable for eight hours at room temperature. Results agree well with those obtained by the USP ⅩⅥ method.This method provides a more rapid, convenient, accurate and simple process for the colorimetric determination of reserpine in pharmaceutical preparations. It also gives a mean deviation of <±2% from the average.