Method development and Validation of Reverse Phase HPLC Method for the Determination of Dithranol in Pharmaceutical Ointment Forms

A series of dilute solutions were prepared in the range of 0.01%, 0.03%,0.06% and 0.09% of the assay concentration (0.5mg /ml) using the standard solutions. Equal volumes (5 il) of each of the above solutions were injected in 6 times and the areas were calculated due to dithranol peak. A simple and rapid reverse phase high performance liquid chromatography (RP-HPLC) method was developed and validated for quantitative determination of dithranol in Ointments. Dithranol was analyzed by using reverse phase Phenomenex C 18 column (4.6mm x 25cm, 5microns) with mobile phase consisting of acetonitrile: water: TFA (60:40:0.05%v/v). The flow rate was set 1.2ml/min and the analysis was performed at wavelength 254nm using Photo Diode Array (PDA) detector at 25°C temperature. The method was validated and stability studies were conducted under different conditions. The retention time for dithranol was around 10.2minutes. The developed method was successfully applied to estimate the amount of dithranol in ointment formulations and it is the stability indicating method.