Simultaneous determination of tretinoin and clindamycin phosphate and their degradation products in topical formulations by reverse phase HPLC.

A new HPLC method based on reverse phase separation and photodiode-array detection has been developed for the simultaneous determination of tretinoin and clindamycin phosphate, and their degradation products in topical formulations. The method has been shown to be stability indicating, accurate, and precise for two different formulation vehicles. Separation was achieved on a reverse phase C18 column (Lichrospher, RP18, 5 microm, 25 cm x 4.