A new efficient capillary zone electrophoresis (CZE) method was established for the first time to determine the dissociation constant (pKa) of acetic acid and monochloroacetic acid. The electroosmotic flow of acetic acid and monochloroacetic acid in the buffer solution of a certain range of pH value was thus separately marked with a neutral marker and the signal of sudden change of current, and the effective mobility curves within a suitable pH range were measured. This, in combination with the regression analysis and fitting of relevant measurement data, makes it feasible to determine the pK. values of acetic acid and monochloroacetic acid. As-measured results are in good agreement with those in literature, which indicates that the present approach can be well adopted to determine the pK, value of to-be-tested compounds with ease, speediness, and reliability.%首次建立了测定一氯乙酸和乙酸的电离常数的高效毛细管区带电泳新方法.该方法利用中性标记物和电流突跃两种方法来标记电渗流,通过测定乙酸和一氯乙酸在一定pH的缓冲溶液中的电泳淌度,结合数据回归分析拟合,求得乙酸和一氯乙酸的电离常数；所得数据和文献报道值较为接近.总体而言,毛细管区带电泳法可简单、快速、可靠地用于测定待测化合物的电离常数.
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