Separation and estimation of five imidazoles by packed column supercritical fluid chromatography

An isocratic, isothermal and isobaric supercritical fluid chromatographic method using packed columns has been developed for the separation and estimation of 5 imidazole, viz., metronidazole, tinidazole, secnidazole, albendazole and mebendazole. Supercritical CO2 doped with methanol has been used as the mobile phase and separations were carried out on a reverse phase octadecyl column packed with 5 μm particles. Detection was with a UV multiwavelength spectrophotometer equipped with a 16 μl cell with a pathlength of 5 mm. The wavelength used was 254 nm. The internal standard method was used, with albendazole serving as internal standard for the other four imidazoles and secnidazole for albendazole (2 sets). A full scale validation of the method of estimation of drugs has been carried out and the viability of the method has been established. The method was successfully extended to pharmaceutical dosage forms available locally.