Rapid identification and quantitation of clotrimazole, miconazole, and ketokonazole in pharmaceutical creams and ointments by thin-layer chromatography-densitometry.

Thin-layer chromatography (TLC)-densitometry was used to separate, identify, and quantitate clotrimazole, miconazole, and ketokonazole (alone or combined with other drugs) in various pharmacopoeial or proprietary creams and ointments. Clotrimazole was extracted from the cream or ointment with ethyl alcohol, and miconazole and ketokonazole were extracted with a mixture of equal volumes of chloroform and isopropyl alcohol. Active ingredients were separated from excipients and other drugs by TLC on a precoated silica gel F254 plate with a solvent system of n-hexane-chloroform-methanol-diethylamine (50 + 40 + 10 + 1, v/v). The 3 azoles were well separated and easily identified in this chromatographic system. The separated azoles were visualized under short-wave UV light and quantitated by scanning densitometry at 220 nm by comparing the integrated areas of samples with those of standard (one azole was used as internal standard for the other). Recoveries from samples spiked with known amounts of azoles were excellent. The method was validated further by comparison with official liquid chromatographic methods.