Analytical Sciences

Abstract − Analytical Sciences, 24(11), 1409 (2008).

Polymeric Membrane Sensors for the Selective Determination of Dextromethorphan in Pharmaceutical Preparations
Eman H. EL-NABY
Narcotic Department, National Center for Social and Criminal Research, P. O. Zamalek Post, 11561, Cairo, Egypt
The construction and electrochemical response characteristics of poly(vinyl chloride) matrix ion-selective electrodes (ISEs) for dextromethorphan (DXM) hydrobromide are described. The membranes incorporate ion-association complexes of DXM with reineckate salt {[Cr(NH3)2(SCN)4]NH4} or phosphomolybdic acid [H3(PMo12O40)], as electroactive materials and dioctylphthalate or dibutylsebacate as a plasticizing solvent mediator. The sensors display a fast, stable and linear response with slopes of 54.4 to 59.5 mV/decade at pH 2.5 - 6.5 and a detection limit of 1.0 × 10-6 M. Moreover, the sensors exhibit very good selectivity for DXM over opiate alkaloids, as well as organic and inorganic cations. The sensors proved to be useful for the determination of 5.0 × 10-5 - 1.0 × 10-3 M DXM hydrobromide in pure as well as in dosage forms by direct potentiometry and standard addition methods. Determination of 5.0 × 10-4 M DXM using the standard addition method and a sensor based on phosphomolybdate and dioctylphthalate shows an average recovery of 99.8% and a relative standard deviation (RSD) of 0.4%.