Use of rose bengal in the colorimetric determination of some anti histamines

ABSTRACT

A precise colorimetric method is described for the estimation of phenyltoloxamine citrate, diphenyltoloxamine hydrochloride and chlorpheniramine maleate. The method depends on ion-pair extraction of association formed between tertiary amines and Rose Bengal [RB]. The reddish-purple ion associated formations were readily extractable in dichloromethane and exhibited maximum at 555 nm. The method obeys Beer's law in the concentration range 2-20 mug ml-1 for diphenylhydramine hydrochloride or chlorpheniramine maleate and 4-40 mug ml-1 for phenyltoloxamine citrate. Optimization of the experimental conditions is described. The proposed method was applied to the analysis of these drugs in pharmaceutical preparations, and results were in good agreement with those obtained by the BP or USP method: