Titrimetric micro determination of some phenothiazine neuroleptics with potassium hexacyanoferrate(III)

摘要

Three simple, rapid and accurate titrimetric procedures using potassium hexacyanoferrate(III) have been developed for the micro determination of five phenothiazine drugs in pure form and in dosage forms. The procedures are based on the oxidation of phenothiazines in an acid medium to colourless sulphoxides via orange or purple coloured products. In the first procedure, phenothiazines are titrated directly in H_2SO_4-H_3PO_4 medium to a colourless end point. In the second method, a known excess of the oxidant is added and after a specified time, and residual oxidant is determined iodometrically. The third method employs electrometric end-point detection. The optimum reactions conditions and other analytical parameters are evaluated. The influence of the substrates commonly employed as excipients with phenothiazine drugs has been studied. Statistical comparison of the results with those of an official method shows excellent agreement and indicates no significant difference in precision.