HPLC with Diode-Array Detection for Determination of Leflunomide in Tablets D. S. Miron 1,& , C. Soldattelli 1,2 , E. E. S. Schapoval 1,2 1 Programa de Po ´s-graduac ¸a ˜o em Cie ˆncias Farmace ˆuticas, Faculdade de Farma ´cia, Universidade Federal do Rio Grande do Sul, Porto Alegre RS, Brazil; E-Mail: diogomiron@hotmail.com 2 Departamento de Produc ¸a ˜o e Controle de Medicamentos, Faculdade de Farma ´cia, Universidade do Rio Grande do Sul, Porto Alegre RS, Brazil Received: 15 December 2005 / Revised: 12 January 2006 / Accepted: 30 January 2006 Online publication: 28 February 2006 Abstract We have developed and validated a simple HPLC method for analysis of leflunomide in tablets. Method conditions were determined by assay of a photodegraded sample of leflunomide. Optimum chromatographic performance was obtained with a C 18 column and acetonitrile- water as mobile phase. Comparison of spectra recorded with a diode-array detector during elution of the leflunomide peak enabled determination of method specificity. The method is highly sensitive (detection limit 10 ng mL )1 ) and robust to deliberate variation of the conditions (RSD of peak area < 2.0%). Precision and accuracy were adequate over the concentration range 10 to 100 lg mL )1 . These results show the proposed method is suitable for its intended use. Keywords Column liquid chromatography Diode-array detection Leflunomide Introduction The quality of pharmaceutical products is of foremost concern in health care. In this context, validation of analytical methods is highly important in development and routine analysis. Assays used for drug quantification must generate accurate and reliable analytical results, to ensure the quality of pharmaceutical products. The tests performed during validation can provide analytical data enabling estimation of the variability and sensi- tivity of the proposed assays and are commercially essential, because many decisions, for example batch release, involve analytical measurements [1–3]. HPLC is widely used for analysis of pharmaceutical products, mostly because of its capacity to analyze mixtures. Diode-array detection increases the power of HPLC and is an elegant option for assessing method specificity by com- parison of spectra recorded during peak detection [4, 5]. In addition, forced deg- radation of samples must be considered during development and optimization of chromatographic conditions, particularly when degraded products are unknown or not available [6, 7]. Leflunomide (Fig. 1) is a prodrug used for treatment of active rheumatoid arthritis. It is an isoxazole derivative marketed as 10, 20, and 100-mg coated tablets [8, 9]. This paper reports the development and validation of an HPLC method for determination of leflunomide in tablets which can be used for quality control. In addition to the typical per- formance characteristics used for valida- tion of an analytical method, this paper also reports results from prevalidation and assessment of the peak-purity profile by diode-array detection. Experimental Chemicals Leflunomide reference substance was kindly supplied by Aventis Pharma (Sa˜o Paulo, Brazil); it was stated to contain 100.2% leflunomide. Tablets labeled to contain 20 mg leflunomide were pur- chased commercially. Acetonitrile for chromatography was purchased from Merck (Darmstadt, Germany). Deionized water was obtained from a Millipore Milli-Q filtration/purification system. Instrumentation and Analytical Conditions HPLC analysis was performed with a Shimadzu HPLC system, equipped with 2006, 63, 283–287 DOI: 10.1365/s10337-006-0739-4 0009-5893/06/03 Ó 2006 Friedr. Vieweg & Sohn/GWV Fachverlage GmbH Short Communication Chromatographia 2006, 63, March (No. 5/6) 283