Investigation of Chromatographic Behavior of Leflunomide and its Identification in Pharmaceutical Dosage form by Reversed Phase Liquid Chromatography

Abstract

Dissociation constant value () is key parameter for predicting the extent of the ionization of a drug molecule at different pH. In this study, pK _a values of leflunomide in different percentages of acetonitrile–water binary mixtures (50%, 55%, and 60%, v/v) were determined from the mobile phase pH dependence of retention factor with reverse phase liquid chromatographic method (RPLC). From calculated pK _a values, the aqueous pK _a value of leflunomide was calculated by various approaches. Moreover, the correlation established between retention factor and the pH of the water–acetonitrile mobile phase was used to determination of optimum separation condition. In order to validate the optimized condition, leflunomide was studied in pharmaceutical dosage form. A Gemini NX C18 column (250 × 4.6 mm I.D., 5 µm particles) was preferred to carry out the developed method. The parameters, linearity, precision, accuracy, specificity, limit of detection, and limit of quantitation were studied according to U.S. Pharmacopeia.

Keywords:

• dissociation constant
• leflunomide
• method validation
• pharmaceutical dosage form
• RPLC
• U.S. Pharmacopeia

Notes

^a Each value is the mean of 5 experiments.

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