Partition Coefficient Measurements in Picoliter Drops Using a Segmented Flow Microfluidic Device

A microfluidic method to rapidly measure the octanol-water partition coefficient in thousands of individual picoliter drops is described. AT-junction microfluidic chip is used to generate a segmented flow of monodisperse, fluorescein-laden water in octanol carrier fluid. The partitioning of individual drops reaches equilibrium in less than 2 s. Epifluorescence microscopy is used measure the partition coefficient of fluorescein as a function of pH. Results compare well with previous measurements using traditional shake-flask methods. The methods presented here are rapid, provide detailed statistics, and can be run in parallel, enabling the simultaneous partitioning of thousands of compounds for various applications such as drug development, environmental testing, and combinatorial chemistry. Microfluidic partitioning and extraction in picoliter drops may be useful for studying molecules and particles away from their equilibrium state and in cases with limited samples.