Table of Contents
ISRN Spectroscopy
Volume 2012 (2012), Article ID 648510, 10 pages
Research Article

Use of Alizarin Red S as an Ion-Pair Reagent for the Spectrophotometric Assay of Fexofenadine in Pharmaceuticals and in Spiked Human Urine

Department of Chemistry, University of Mysore, Manasagangotri Campus, Mysore, Karnataka 570006, India

Received 19 October 2012; Accepted 19 November 2012

Academic Editors: C. Liang and I. Milošev

Copyright © 2012 Madihalli S. Raghu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The present study describes two simple, rapid, selective, and cost-effective spectrophotometric methods for the determination of an antiallergic drug, fexofenadine hydrochloride (FFH), in bulk drug, tablets, and in spiked human urine. The first method (method A) is based on the formation of yellow-colored ion-pair complex between FFH and alizarin red S (AZS) in acid medium which was extracted into dichloromethane, and the absorbance was measured at 440 nm. The second method (method B) is based on the breaking of the yellow FFH–AZS ion-pair complex in alkaline medium followed by the measurement of the violet-colored free dye at 590 nm. Under the optimized conditions, Beer’s law is obeyed over the concentration ranges of 0.4–12.0 and 0.2–3.5 μg  FFH for method A and method B, respectively, and the corresponding molar absorptivity values are 3.80 × 104 and 1.61 × 105 L  . The Sandell’s sensitivity, detection, and quantification limits are also reported. The proposed methods were successfully applied to the determination of FFH in pure drug and commercial tablets. The accuracy and reliability of the proposed methods were further established by recovery studies via standard addition technique.