Colorimetric determinations of chlorpheniramine maleate, ephedrine hydrochloride, and guaiacolsulfonate potassium in a cough syrup.

Colorimetric methods for the quantitative determinations of chlorpheniramine maleate, ephedrine hydrochloride, and guaiacolsulfonate potassium in a cough syrup containing color (amaranth) are reported. Chlorpheniramine maleate can be assayed using the cyanogen bromide method as reported in the literature. Ephedrine hydrochloride can be assayed using a dye method in which interference from chlorpheniramine maleate is taken into consideration. Guaiacolsulfonate potassium can be assayed by coupling it with 4-aminoantipyrine (the method is similar to the one for phenylephrine hydrochloride). All of the methods are simple, accurate, and precise. The application of the guaiacolsulfonate potassium assay method to commercial dosage forms is reported.