Abstract
Three simple, rapid and accurate titrimetric procedures using potassium dichromate as titrant are described for the determination 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 evaluated and the molar-ratio of the reaction is also calculated. The influence of the substrates commonly employed as excipients 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.
