Microfluidics approach for determination of the equilibrium phase composition in multicomponent biphasic liquid systems

Based on the fundamentals of microfluidics, a novel approach for the determination of liquid-liquid equilibria (LLE) of ternary systems was proposed. The system studied here consists of the compounds water, acetone, and toluene. This method was realized in a microfluidic set-up that consists of a microchannel, a camera for the determination of the position of the phase interface, and a micro density meter for measuring the densities of the conjugated phases at the outlet of the microchip. To determine the equilibrium phase compositions, an optimization problem was defined that minimized the difference between the experimentally determined and calculated ratio of the volumetric flow rates of the conjugated phases. The developed procedure uses information on the position of the phase interface in the microchannel and the phase densities, and requires previous knowledge of the binodal curve, which as shown in our previous work (Hübner and Minceva, 2019) can be also determined using the same set-up. The obtained equilibrium phase compositions were in good agreement with literature data. Eventually, once the procedure is automatized to reduce the required measuring time and achieve full user independency, the proposed approach poses a cheap and fast alternative to conventional methods for measuring LLE.