Simultaneous determination of corticosteroids and parabens in ointments by HPLC

A rapid, simple and reliable method was developed for the simultaneous determination of eleven corticosteroids, such as prednisolone, triamcinolone acetonide, fluocinolone acetonide, hydrocortisone butyrate, fluocinonide, difluprednate, dexamethasone valerate, betamethasone valerate, prednisolone valerate-acetate, beclomethasone dipropionate and diflucortolone valerate, and four parabens, such as methyl, ethyl, n-propyl and n-buthylparaben in ointments by HPLC. The method involves a clean-up on a disposable SepPak silicagel cartridge. Fat-soluble excipients are removed through the cartridges with 10 ml of hexane-chloroform (70 : 30). Corticosteroids and parabens are then eluted from the cartridges with 10 ml of ethyl acetate and determined by HPLC on a reversed-phase column with water-methanol (50 : 50 and 60 : 40) as the mobile phase, and detected at 240 nm with 0.04AUFS using s-butylparaben as an internal standard. The method was successfully applied to the analysis of ointement base spiked corticosteroids and parabens, and the sufficient recoveries (98.4103.2%) were obtained with relative standard deviation of 0.42.4%.