Separation and estimation of diloxanide furoate and metronidazole in solid dosage form using packed column supercritical fluid chromatography

A reproducible and efficient method for the simultaneous determination of metronidazole and diloxanide furoate from its pharmaceutical solid dosage form has been developed using packed column supercritical fluid chromatography. The separation was done using a JASCO-C-18 (250×4.0 mm) 10 μ column, with methanol modified supercritical fluid CO2 as the mobile phase. The internal standard method using tinidazole as the internal standard was employed. The densities and polarities of the mobile phase were optimised from the effects of pressure, temperature and modifier concentration on the retention time. The analytes were detected at 230 nm. Chromatographic figures of merit, calibration data, and recovery of the drug from spiked concentrations were determined to assess the viability of the method. The method has been successfully used to analyse a commercial solid dosage form labelled to contain 400 mg of metronidazole and 500 mg of diloxanide furoate. The same method can also be employed for the simultaneous estimation of tinidazole and diloxanide furoate from its pharmaceutical dosage form using metronidazole as the internal standard.