Abstract
Potentiometric determination of methylene blue in pharmaceutical preparation using simple PVC electrode
Author(s): Elmorsy Khaled, M.A.Elries, F.I.Zidane, S.Shaban, M.S.Abdel-MonemThe construction and performance characteristics of methylene blue (MB) PVC electrodes are described. Different methods for electrode fabrication (modified with the ion-pair, ion pairing agent or soaking the plain electrode in the ion-pair suspension) are described. Matrix compositions were optimized on the basis of effects of type and content of the modifier as well as influence of the plasticizers. The fabricated electrodes worked satisfactorily in the concentration range from7ï‚´10-8 to 10-3Mwith Nernstian cationic slopes depends on the method of electrode fabrication. TheMB-TPB modified electrode showed the best performance (slope 58.3±2.0 mV decade-1) compared with the plain electrodes or modified with NaTPB and fast response time of about 10 sec and adequate lifetime (2 months). The developed electrodes have been successfully applied for the potentiometric determination ofMB in pure solution and in pharmaceutical preparations under batch conditions as well as end point indicator electrode for the potentiometric titration of MB. The solubility product of different MB ion-pair and the formation constant of the precipitation reaction leading to the ionpair formationwere determined conductometrically.
