INDIVIDUAL AND SIMULTANEOUS DETERMINATION OF EPHEDRINE AND PHENYLEPHRINE BY USE OF KINETIC METHODOLOGY

Kinetic methodology was for the first time used to develop a simple ph otometric method for the determination for ephedrine and phenylephrine using the stopped-flow mixing technique. The method involves oxidatio n of these compounds and kinetic monitoring of the reactions of the al dehydes formed with 2-methylbenzothiazoline-2-one hydrazone in the pre sence of iron(III) chloride to give the corresponding coloured formaza ns. Ephedrine and phenylephrine can be determined simultaneously by ap plying the proportional-equation method to the reaction rate and absor bance amplitude of the kinetic curves obtained for each analyte. The c alibration graph was linear over the range 0.7-70.0 mu g mL(-1) ephedr ine and 1.2-70.0 mu g mL(-1) phenylephrine. The proposed method was ap plied to the determination of ephedrine in pharmaceutical samples with a mean recovery of 103.2%. Synthetic mixtures of ephedrine and phenyl ephrine in ratios between 3:1 and 1:5 were satisfactorily resolved.