报道了利用 ３０ ｍｍｌ／Ｌ ＨＡｃ－ＮａＡｃ为缓冲液测定复方新诺明中甲氧苄胺嘧啶（ＴＭＰ）和磺胺甲基异噁唑（ＳＭＺ）的离解常数及含量的毛细管区带电泳（ＣＺＥ）方法。该方法具有简便、快速、准确等特点。测得ＴＭＰ和ＳＭＺ的ｐＫａ分别为６．６０和５．９０。其平均回收率分别为１０１．５％和９９．６％，最低检出限为０．４８ ｍｇ／Ｌ和０．０２８ ｍｇ／Ｌ，ＲＳＤ为１．２６％和１．１２％。 Reported the determination of the dissociation constants and contents of trimethoprim (SMP) and sulfamethoxazole (SMZ) in cotrimoxazole with 30 mml / L HAc-NaAc as buffer solution by capillary zone electrophoresis (CZE) method. The method is simple, fast and accurate. The pKa of TMP and SMZ were measured as 6.60 and 5.90, respectively. The average recoveries were 101.5% and 99.6%, respectively, and the lowest detection limits were 0.48 mg / L and 0.028 mg / L with RSDs of 1.26% and 1.12%, respectively.