(472c) Electrochemical Sensor-Integrated, Continuous Flow, Microfluidic Device for Real-Time Measurement of Supersaturation during Salt Screening

Electrochemical sensors can offer quick and robust detection of organic molecules inside microfluidic devices where the amount of sample is small. These sensors can be assembled with a feedback control unit for automatic adjustments of flowrates to obtain higher experimental accuracy. The sensor-integrated microfluidic system can facilitate high-throughput screening of crystalline materials in shorter time by precisely controlling the concentration of organic molecules in each microwell. In this study, a continuous microfluidic mixer is coupled with an electrochemical sensor to enable in-situ measurement of solute concentration in the mixing zone. The sensor consists of three electrodes: working, contour, and reference connected externally to a potentiostat. The electrodes are inserted into the microfluidic mixer horizontally. Here we have used Pt and Ni wires as the counter and working electrodes, respectively. Cyclic Voltammetry (CV) is performed during the continuous operation of the microfluidic device which correlates to the concentration of Naproxen. This sensor integrated microfluidic device is experimentally evaluated for the salt screening of Naproxen. Screening of solid salt forms of Naproxen includes four solvents and four salt formers (SFs) which results in sixteen experimental conditions. All experiments are performed under an optical microscope for in-line measurements of crystals' morphology and growth rates. After the concentration measurement and salt formations, crystallized salts are harvested for PXRD and particle size distribution analysis.