目的 建立高效液相色谱法同时测定复方头孢氨苄胶囊中头孢氨苄和甲氧苄氨嘧啶的含量。方法 采用Spherisorb C〈sub〉18〈/sub〉柱，流动相为0.025 mol·L〈sup〉-1〈/sup〉磷酸溶液(用三乙胺调节pH=3.0)-乙腈(88∶12)，检测波长240 nm。结果 头孢氨苄及甲氧苄氨嘧啶分别在10～100 μg·ml〈sup〉-1〈/sup〉(r=0.9998,n=5)，2～20 μg·ml〈sup〉-1〈/sup〉(r=0.9996,n=5)浓度范围内呈线性关系，平均回收率分别为 99.59%，99.73%；RSD 分别为0.28%，0.44%。结论 本方法对流动相系统作了改进，方法简便、快速、准确，在降解产物较多时也适用。

OBJECTIVE To establish an HPLC method for the determination of cefalexin and trimethoprim in compound cefalexin capsules. METHODS The spherisorb C₁₈colunm was used.The mobile phase was consisted of 0.025 mol·L^-1phosphoric solution (pH was adjusted to 3.0 with triethylamine)-acetonitrile (88∶12).Detection wavelength was at 240 nm. RESULTS The standard curves for cefalexin and trimethoprim were linear over the range of 10～100 μg·ml^-1(r=0.9999,n=5) and 2～20 μg·ml^-1(r=0.9996,n=5) respectively.The average recoveries of cefalexin and trimethoprim were 99.59%,99.73%,with RSD 0.28%,0.44% respectively. CONCLUSION The mobile phase system was improved,So the method was convenient,rapid,accurate,precise and it was not influenced when there are the degradation products.