Rapid determination of partition coefficients of pharmaceuticals by phase distribution and microchip capillary electrophoresis with contactless conductivity detection

A simple microchip CE method integrated with contactless conductivity detection was developed for the direct determination of partition coefficients of selected pharmaceuticals after phase distribution equilibrium. The equilibrium of distribution between two phases for four pharmaceuticals was performed using a 1-octanol/water system and 1-octanol/buffer system. During the concentration determination, several major factors affecting detection were investigated in detail for each pharmaceutical to optimize the detection sensitivity. In the optimal conditions, sufficient electrophoretic separation and sensitive detection for each target analyte can be achieved within 40 s. The two systems showed a pH-dependent partition behavior. Moreover, the measured values showed excellent agreement with those obtained by the traditional shake-flask method with HPLC-UV detection and literature reports, respectively. The developed method can be successfully applied to measure partition coefficient values of pharmaceuticals and requires much shorter analytical time compared to traditional methods.