An application of eosin Y for the selective spectrophotometric and spectrofluorimetric determination of mebeverine hydrochloride

Two rapid and simple methods were developed and validated for the selective determination of mebeverine hydrochloride based on a binary complex formation with eosin Y. In the spectrophotometric method, the absorbance of the formed complex was measured at 551 nm. Beer's law is obeyed in the range of 1–12 μg ml −1 , the calculated formation constant was 3.95 × 10 5 and the Gibb's free energy change was −3.1 × 10 3 J mol −1 . The spectrofluorimetric method depends on measuring the quenching effect of the drug on the native fluorescence of eosin Y at 540 nm after excitation at 390 nm. At the optimum reaction conditions, the rectilinear calibration graph between the fluorescence quenching values (Δ F ) and the drug concentration was obtained in the drug concentration range of 0.2–3.5 μg ml −1 . The analytical performance of both methods was fully validated, and the results were satisfactory. The selectivity of the methods was evaluated by studying the interference liability of the co-formulated drugs such as sulpiride, metronidazole, dimethicone and diloxanide. None of them interfered. The methods were applied successfully for the assay of mebeverine hydrochloride in commercial tablets containing the drug alone or in combination with other drugs.