Sensitive Extractional Colorimetric Analysis of Fexofenadine Hydrochloride and Irbesartan Bases Through Acid-Dye Complexation Using Naphthol Blue Black in Pure Form and Pharmaceuticals

A simple, accurate and sensitive method has been presented for the determination of fexofenadine hydrochloride (FEX) and irbesartan (IRB) in bulk and pharmaceutical preparations. The method is based on the reaction of the above cited drugs with naphthol blue black (NBB) dye in solutions containing Britton buffer to form ion-pair complexes extractable with chloroform and subsequently measured spectrophotometrically at 625 nm. All the reaction conditions for the proposed methods have been studied. The reactions were extremely rapid at room temperature and the absorbance values remained unchanged for at least 24 hrs. Beer's law was obeyed in the concentration ranges 2.7–53.8 and 10–244 μg mL -1 with detection limit of 0.013 and 0.75 μg mL -1 for FEX and IRB, respectively. The proposed methods were applied successfully for the determination of FEX and IRB in pharmaceutical formulations. Interferences of the other ingredients and excipients were not observed. The results obtained were compared statistically with those obtained by the official method and showed no significant differences regarding accuracy and precision.