POTENTIOMETRIC AND SPECTROPHOTOMETRIC DETERMINATION OF PHENOTHIAZINE DERIVATIVES BASED ON THEIR TITRATION WITH 2,3-DICHLORO-5,6-DICYANO-1,4-BENZOQUINONE
Khalil Farhadi,a Mojtaba Shamsipurb*
a Department of Chemistry, Urmia University, Urmia, Iran
b Department of Chemistry, Razi University, Kermanshah, Iran
The reaction between phenothiazine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in the presence of p-toluenesulfonic acid in chloroform was investigated by potentiometry, voltammetry and spectrophotometry, and the reaction pathways were proposed. The conditions for the oxidimetric titration of phenothiazines with a standard chloroform solution of DDQ were optimized and the potentiometric and spectrophotometric detections of the reaction end point were utilized. The relative standard deviations for the potentiometric determination of 3-5 mg phenothiazines and for the spectrophotometric determination of 0.1-0.2 mg phenothiazines were found to be about 1.2-1.7% and 0.8-1.2%, respectively. The proposed methods were applied to the determination of phenothiazine derivatives in pharmaceutical preparations after their extraction into chloroform.