Development of difference spectrophotometric method for the estimation of leflunomide in tablet dosage form

A new simple, accurate, precise, highly sensitive and reproducible difference spectrophotometric method for the determination of leflunomide in bulk and pharmaceutical dosage form is described. Difference spectroscopic method is based on the principle that leflunomide exhibit two different forms; in acidic and basic medium which differs in their absorption spectra. The difference spectra were obtained by reading the absorbance of leflunomide in 0.1N HCl in the reference cell and the absorbance of leflunomide in 0.1N NaOH in the sample cell and vice versa; in the difference spectrum maxima and minima were seen at 293.5nm and at 261.5nm respectively. The amplitude values were calculated, which was plotted against concentration. The method is found to be linear in the concentration range of 2-12 μg/ml. The percentage recovery was found to be between the ranges from 98.92 % to 99.08 %. The proposed method was statistically validated and successfully applied for analysis of tablet dosage forms.