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目的：研究广泛ｐＨ范围内来氟米特的化学稳定性。方法：建立来氟米特的ＨＰＬＣ测定方法，测定不同温度下不同ｐＨ值时来氟米特分解的速度常数，得到不同ｐＨ值时的分解活化能及不同温度下的最稳定ｐＨ值。结果：常温（２０～４０℃）下来氟米特最稳定的ｐＨ范围是２．８５～４．５６，活化能数值恰在此范围内出现极大值。最稳定的ｐＨ范围随温度升高而向低ｐＨ值方向移动，当温度大于６０℃时，最稳定ｐＨ值为１．８０以下。结论：适当调整溶液的ｐＨ值可以显著改善来氟米特的化学稳定性，为其制剂学研究提供了部分依据。
Objective: To study the chemical stability of leflunomide over a wide range of pH. Methods: The HPLC method for the determination of leflunomide was established. The rate constant of leflunomide decomposition at different pH values was determined. The decomposition activation energy at different pH values and the most stable pH values at different temperatures were obtained. Results: The most stable pH range of leflunomide at room temperature (20-40 ℃) was 2.85-4.56, and the activation energy reached the maximum just within this range. The most stable pH range moves toward lower pH with increasing temperature and the most stable pH below 1.80 at temperatures greater than 60 ° C. Conclusion: Appropriate adjustment of the pH value of the solution can significantly improve the chemical stability of leflunomide, which provides a basis for the preparation of the study.