Validated spectrophotometric methods for the determination of raloxifene hydrochloride in pharmaceuticals

Abstract

Two new simple, precise, rapid and extraction-free spectrophotometric methods are proposed for the determination of raloxifene hydrochloride (RLX) using bromate-bromide mixture and two dyes, methylene blue and rhodamine B, as reagents. The methods entail the addition of a known excess of bromate-bromide mixture to RLX in hydrochloric acid medium followed by determination of residual bromine by reacting with a fixed amount of either methylene blue and measuring the absorbance at 665 nm (Method A) or rhodamine B and measuring the absorbance at 555 nm (Method B). The amount of bromate reacted corresponds to the amount of RLX. In both the methods, the absorbance is found to increase linearly with the concentration of RLX. Under the optimum conditions, RLX could be assayed in the concentration ranges 0.5-5.0 and 0.1-2.0 μg mL-1 from method A and method B, respectively. The apparent molar absorptivities are calculated to be 7.0 × 104 and 1.1×105 L mol -1cm-1 for method A and method B, respectively, and the corresponding Sandell sensitivity values are 0.0073 and 0.0048 μg cm -2. The limits of detection and quantification have also been reported for both the spectrophotometric methods. The overall reproducibility of the methods was excellent and recoveries were 98.3-102.5% and 98.2-103.2% for method A and method B, respectively. The proposed methods can be readily utilized for bulk drug and in pharmaceutical formulations.