Abstract: AimTo establish a novel microemulsion electrokinetic chromatography (MEEKC) method for measuring lipid-water partition coefficients (logP_ow) of pharmaceuticals without using microemulsion phase marker in order to avoid the error from tracing the migration time of microemulsion phase. MethodsThe migration time of microemulsion phase (t_me) was obtained by non-linearity fitting with logP_ow values from literature and measured migration time (t_m) of a series of organic compounds, a calibration curve for estimating logP_ow of pharmaceuticals was thus obtained. In addition, the accuracy of the values measured by MEEKC was evaluated. ResultsThe logP_ow values of 4 pharmaceuticals measured by MEEKC method presented in this paper were close to those determined by shake-flask method, and the average error between values from two methods was 0.15 logarithm units. Furthermore, according to the suggested theory, the measurement accuracy of logP_ow is correlated with different t_m in MEEKC. ConclusionThe proposed method is simple, rapid, reproducible, and reliable with high measurement accuracy, which can be useful to estimate lipid-water partition coefficients of pharmaceuticals.