Determination of chlorpheniramine maleate, dihydrocodeine bitartrate and ephedrine hydrochloride in cough mixture by derivative and differential spectrometry.

A method is presented for the determination of chlorpheniramine maleate, dihydrocodeine bitartrate and ephedrine hydrochloride in a three-component mixture without prior separation. Chlorpheniramine maleate was determined by the first and second derivative-differential spectrophotometry, while dihydrocodeine bitartrate was directly determined using first and second derivative measurements. Ephedrine hydrochloride could be determined by first and second derivative spectrophotometry after its oxidation with sodium metaperiodate. The method was proved using synthetic mixtures of these drugs and was applied for their determination in syrup with a coefficient of variation less than 2%.