Potentiometric determination of ephedrine hydrochloride using plastic membrane ion-selective electrode.

A plastic membrane electrode based on phenylephrine-tetraphenylborate ion association shows a Nernstian response to both ephedrinium (Ep+) and silver (Ag+) cations over the concentration ranges 2 x 10(-5)-10(-1) M and 10(-5)-10(-1) M for Ep+ and Ag+, respectively. The performance characteristics of the electrode were investigated. The electrode proved to be an excellent potentiometric sensor for the determination of Ep-hydrochloride in its pure solutions and pharmaceutical preparations using the extrapolation method and potentiometric titration using a standard solution of AgNO3.