Use of Iron (III) Chloride for the Sensitive and Selective Assay of Etamsylate in Pharmaceuticals

Two simple and selective spectrophotometric methods have been proposed for the assay of etamsylate (ETM) in bulk and dosage forms. The first method (method A) is based on the reaction of ETM with ferric chloride in dimethylformamide (DMF) medium to form a colored species with a λmax at 655 nm. The second method (method B) is based on the oxidative coupling reaction involving ETM, 3-methyl-2-benzothiazolinone hydrazone (MBTH) and ferric chloride in the presence of sodium acetate which yielded a bright pink colored chromogen with λmax.at 520 nm. The amount of chromogen formed corresponds to the amount of ETM and the measured absorbance is found to increase linearly with the concentration of ETM, which is corroborated by the correlation coefficient of 0.999 in both the methods. Under optimum conditions, Beer’s law is obeyed over the ranges 4.0-140 and 1.5-30 μg mL^-1 for method A and method B respectively. The calculated molar absorptivity values are 1.68 × 10³ and 7.83 × 10³ L moL^-1 cm^-1 for method A and method B, respectively and the corresponding sandell sensitivities are 0.156 and 0.033 μg cm^-2. The proposed methods were applied to the analysis of tablet forms of ETM and the results tallied well with the label claim. No interference was observed from concomitant substances normally added to tablets. The results were statistically compared with those of a literature method by applying the Student’s t-test and F-test. The accuracy and validity of the methods were further ascertained by performing recovery studies via spike method.