Authors : D. M. Chafle
Page Nos : 351-354
Description :
Promethazine hydrochloride is phenothiazine used as antipsychotic drug. A simple, rapid and sensitive extractive spectrophotometric method is described for the determination of promethazine hydrochloride in pure form and in its pharmaceutical formulation. The method is based on the ion-pair complex formation between the drug and the Congo red dye in acidic medium. The red coloured chromogen, being extractable with chloroform, could be measured quantitatively at 483 nm. All variables were studied to optimize the reaction conditions. The method obeys Beer's law and the precision and accuracy of the method were checked. The molar composition and stability constant of the ion –pair complex formed is determined at room temperature by Turner and Anderson method . The molar composition of complex Congo red : PromethazineHCl is 1:2. The stability constant is 1.2489 x 104. The detection limit is 19.4 to 83.5 μg m1-1 and the molar absorptivity is 3.5298 x 103 L mol-1 cm-1 and Sandell’s sensitivity is 0.1125 μg cm-2 per 0.001absorbance unit.
Key words: Extractive spectrophotometry, ion-pair complex, promethazine hydrochloride, congo red.
