Ion Association Methods Development for the Assay of Venlafaxine Hydrochloride Using Two Acidic Dyes

Two simple, rapid and sensitive extractive visible spectrophotometric methods (A and B) for the assay of venlafaxine hydrochloride in pure and solid dosage forms based on the formation of colored chloroform soluble ion - association associates under specified experimental conditions are described. Two dyes namely acidic dyes Naphthalene Blue 12BR (NB12BR, method A) and Bromo Cresol Purple (BCP, method B) are utilized. The extracts of the ion-associates exhibit absorption maxima at 620.5 nm and 430 nm for methods A and B respectively. Regression analysis of Beer- Lambert plots showed good correlation in the concentration ranges (4.0 -12.0) μg/ml for method A, (8.0-40.0) μg/ml for method B respectively. The proposed methods are applied to commercial available tablets and the results are statistically compared with those obtained by the UV reference method and validated by recovery studies. The results are found satisfactory and reproducible. These methods are applied successfully for the estimation of the venlafaxine hydrochloride in the presence of other ingredients that are usually present in dosage forms. These methods offer the advantages of rapidity, simplicity and sensitivity and normal cost and can be easily applied to resource-poor settings without the need for expensive instrumentation and reagents.