Simple colorimetric method for determination of metaproterenol sulfate in pharmaceuticals

A simple colorimetric method is described for the determination of metaproterenol sulfate (orciprenaline sulfate). The method is based on measurement of a colored species formed when metaproterenol sulfate is treated with diazotized dapsone, p-nitroaniline, or benzocaine at room temperature, followed by treatment with an aqueous solution of trimethylamine in the case of benzocaine. Compounds such as starch, talc, and common excipients do not interfere in the reaction. Statistical validation showed that the method was precise and accurate. The results agree well with those obtained by other methods reported in the literature.