Micellar HPLC method for simultaneous determination of ethamsylate and mefenamic acid in presence of their main impurities and degradation products

An eco-friendly sensitive, rapid and less hazardous micellar liquid chromatographic method was developed and validated for the simultaneous analysis of ethamsylate (ETM) and mefenamic acid (MFA) in the presence of hydroquinone (HQ) and 2,3-dimethylaniline (DMA) the main impurities of ETM and MFA, respectively. Good chromatographic separation was attained using Eclipse XDBC8 column (150mm × 4.6 mm, 5 μm particle size) adopting UV detection at 300 nm with micellar mobile phase consisting of 0.12M sodium dodecyl sulfate, 0.3% triethylamine and 15% 2- propanol in 0.02M orthophosphoric acid (pH 7.0) at 1.0 mL/min. The analytes were well resolved in <6.0 min, ETM (t_R = 1.55 min), HQ (t_R = 1.95 min), MFA (t_R = 4.55 min) and DMA (t_R = 5.80 min). Different validation parameters were examined as recommended by international conference on harmonization (ICH) guidelines. The method was linear over the concentration ranges of 0.5-18.0, 0.5-20.0, 0.01-0.5 and 0.02-0.2 μg/mL with limits of detection of 0.118, 0.159, 0.005 and 0.005 μg/ mL and limits of quantification of 0.358, 0.482, 0.014 and 0.015 μg/mL for ETM, MFA, HQ and DMA, respectively. The suggested method was successfully applied for the determination of the two drugs in their bulk powder, laboratory-prepared mixtures, single-ingredient and co-formulated tablets. The obtained results were in accordance with those of the comparison method. The method can also detect trace amounts of HQ and DMA as the main impurities of ETM and MFA, respectively, within the BP limit (0.1%) for both impurities. Furthermore, it is a stability-indicating one for the determination of ETM in its pure form, single-component tablet and co-formulated tablets with other drugs.