Contactless mass transfer for intra-droplet extraction

Abstract

This study demonstrates the possibility of "contactless" mass transfer between two aqueous slugs (droplets) separated by an oil slug in Taylor flow inside milli-channels. Separation of the alternating aqueous slugs at the outlet was performed by switching a couple of solenoid valves at branched outlets according to signals obtained by an optical sensor at the branch. Transfer of bromothymol blue (BTB) from acidic to basic aqueous slugs was performed for demonstration. In some cases, aqueous slugs separated by oil, merged catching on each other due to the velocity difference. Interfacial tension which was affected by the solute concentration was responsible for the velocity difference. Position-specific mass transfer activity at the rear end of the aqueous slugs was found on the course of the experiment. A meandering channel decreased the velocity difference and enhanced mass transfer. Almost complete (93%) transfer of BTB was achieved within a short residence time of several minutes under optimized conditions. The presented system opens a way for advanced separation using minimum amounts of the oil phase and allows concentrating the solute by altering relative lengths of the sender and receiver slugs.

Analysis of Stereochemical Stability of Dynamic Chiral Molecules Using an Automated Microflow Measurement System

“…The flow rate, temperature of the oil bath, and sample injection were automatically controlled using a bespoke software, 13 which performed a stepwise operation based on predefined measurement conditions in an input spreadsheet file. The feeding time for each condition was set to be 5 times longer than the residence time in the microvessel to obtain a steady state of the flow system.…”

“…Dry THF, CH 2 Cl 2 , and MeOH were purchased from Kanto Chemical Co., Inc. and used without further purification. 1 H NMR and 13 C NMR spectra were recorded on a Varian Mercury (300 MHz for 1 H and 75 MHz for 13 C) at ambient temperature using CDCl 3 as a solvent. Chemical shifts (δ) in parts per million were referenced to CHCl 3 for 1 H NMR (δ 7.26) and CDCl 3 for 13 C NMR (δ 77.1) as internal standard.…”

“…1 H NMR (300 MHz, CDCl 3 ): δ 10.2 1H),7.29 (dd,J = 8.5,8.5 Hz,1H),6.68 (dd,J = 8.5,1.5 Hz,1H),6.45 (dd,J = 8.5,1.5 Hz,1H), 1.01 (s, 9H), 0.26 (s, 6H). 13 C{ 1 H} NMR (75 MHz, CDCl 3 ): δ 155. 3, 151.9, 135.3, 129.6, 112.5, 111.0, 25.8, 18.4, −4.3.…”

Multiphase alternated slug flows: Conditions to avoid coalescence and characterization of mass transfer between droplets

“…The transport in ASF has been so far seldom studied. Asano et al [24] have reported qualitative observations on the transport in ASF (without gas) with very long droplets (L d >1cm). They observed a concentration gradient between the front and rear caps of the receiving droplet and proposed a transfer mechanism where the film plays an important role in the solute transport.…”

“…The formation of this L/L/L segmented flow, called the alternated segmented flow (ASF), has been investigated in the literature in small square microchannel (internal diameter <500 µm) [19]- [23] with the generation of different flow regimes (merging, alternating, small droplets and laminar) depending on the operating conditions [19], [20]. Very recently, a device to generate alternated segmented flow in circular PFA tubing (i.d of 2.18mm) using a system of valves to control the phase injection has been developed [24]. This work offers a simpler way to generate alternated segmented flow without the need of active control at the injection.…”