Analytical Sciences

Oxidimetric Titration of Some Phenothiazine Neuroleptics and Antiallergics with Potassium Dichromate

K. BASAVAIAH* * and G. KRISHNAMURTHY**

*Department of Studies in Chemistry, University of Mysore, Manasagangothri, Mysore-570 006, India
**Department of Chemistry, PES College of Science, Mandya-571 401, India

Three simple, rapid and accurate titrimetric procedures using potassium dichromate as titrant are described for the deter-mination of six phenothiazine drugs in a pure form and in dosage forms. The procedures are based on the oxidation of phenothiazines in an acid medium to colorless sulfoxides via orange- or purple-colored intermediates. In the first method, phenothiazines are titrated directly in a H2SO4 medium to a colorless end-point. In the second procedure, a known excess of oxidant is added, and after a specified time the residual oxidant is determined iodometrically. The third method employs potentiometric end-point detection. The optimum reaction conditions and other analytical parameters are evalu-ated and the molar-ratio of the reaction is also calculated. The influence of the substrates commonly employed as excipi-ents with phenothiazine drugs has been studied. A statistical comparison of the results obtained for pure drugs with those of an official method shows excellent agreement and indicates no significant difference in precision. (Keywords: Phenothiazine, titrimetric methods, potentiometric end-point detection, potassium dichromate)

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