Continuous-flow microfluidic method for octanol-water partition coefficient measurement

To determine the octanol–water partition coefficient (log Kow or log D), a microfluidic method is developed to reduce time and coast of analyze. A double Y serpentine microfluidic chip is fabricated used soft lithography facilities. To generate a biphasic parallel flow, hydrophilic microchannels walls are generated by oxygen plasma treatment. Epifluorescence microscopy is used to measure the intensity of fluorescence molecules in microchannel. Using microfluidic parallel diluter this intensity show a strong linear correlation with molecule concentration in solution. The equilibrium between phases is reached in less than 5 s. To validate this microsystem, we have determined the log D of fluorescein natrium molecule. The obtained results compare well with previous measurements using traditional shake-flask or microfluidic drops flow methods, with a relative difference to the literature less than 3%. Rapid microfluidic partition coefficient determination is useful for studying liquid–liquid partition of organic pollutant.