Validated Spectrophotometric Approaches to the Determination of Teriflunomide in Active Pharmaceutical Ingredients and Pharmaceutical Dosage Forms

Two simple UV spectrophotometric approaches were developed for the estimation of teriflunomide in both the drug substance and its pharmaceutical dosage form, even in the presence of its two main impurities (namely, A and B). Both approaches involve manipulation of ratio spectra in the range of 200–400 nm using impurity B as a divisor. The first approach involves the dual-wavelength ratio spectra method, which revealed that the absorbance difference between 258 and 301 nm is directly proportional to the concentration of teriflunomide, while impurity A shows the same absorbance. The second approach involves constructing a first derivative of the ratio spectra, with 291 nm identified as the optimum peak amplitude for teriflunomide and a zero crossing for impurity A. Validation of the developed approaches was conducted following the International Conference on Harmonization guidelines. Calibration curves were constructed with linearity ranges of 1.25–10 µg/mL of teriflunomide for both approaches. The limit of detection was found to be 0.25 µg/mL, and the limit of quantitation was found to be 0.625 µg/mL for both approaches, demonstrating good sensitivity of the proposed approaches.