Supercritical extraction of vanillin in a microfluidic device

Supercritical fluids offer great solvent capacities and can be used to render extraction processes greener and safer. Their application to microreactors has been limited to the use as reaction medium, as separation is difficult, due to the low impact of gravitational forces, compared to surface forces. We now realized an integrated silicon/glass microextractor for the continuous supercritical extraction. Efficient contacting of the supercritical solvent and the liquid phase is provided by a segmented flow pattern. Separation can be achieved by capillary forces and adjusted pressure drops. The successful operation is demonstrated by the extraction of vanillin using supercritical carbon dioxide as solvent at pressures from 80 to 110 bar. Concentrations of vanillin in both phases were measured with good reproducibility and distribution coefficients were found to increase with pressure, which is in good agreement with literature. Mass balance considerations additionally confirm the working principle of the device.

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► Suprercritical extraction was successfully conducted in a microfluidic device.
► On-chip separation of a supercritical fluid from a liquid by capillary forces.
► Efficient mass transfer through segmented flow between a liquid and a sc fluid.
► Distribution coefficients of vanillin in water and scCO2 were measured reproducibly.
► Microreactors serve as a safe and economic tool for supercritical extraction.