Assay of Terbinafine Hydrochloride by Extractive-Spectrophotometry with Alizarin Red S-A Modified Approach

Abstract

Terbinafine hydrochloride (TBH) is a new antifungal agent widely used for the treatment of many contagious
diseases. Two spectrophotometric methods based on ion-pair complexation reaction are described for the
determination of TBH. The first method is based on the formation of ion-pair complex between TBH and
alizarin red S (ARS) dye in HCl medium followed by its extraction into methylene chloride and measurement at
450 nm (method A). The other method entails breaking of drug-dye complex in alcoholic KOH medium and
measuring the absorbance of the blue dye at 570 nm (method B). The experimental conditions for selective and
sensitive assay were optimized, and the drug-dye stoichiometry was found to be 1:1. Beer’s law was obeyed over
the concentration ranges 2.5-60, and 4-24 µg mL-1 for method A and method B, respectively, and the
corresponding molar absorptivity values were 5.92×103
and 4.93×103
L mol-1 cm-1, respectively. The limits
detection (LOD) and quantification (LOQ) values were calculated to be 0.22 & 0.66 (method A) and 0.35 & 1.05
(method B). In addition, the methods were also validated with respect to accuracy, precision, robustness,
ruggedness and selectivity. The two methods were applied to the analysis of tablets with no evidence of
interference from excipients.