Analytical Sciences

Tube Radial Distribution of Solvents Observed in an Aqueous Ionic Liquid Mixed Solution Delivered into a Capillary Tube

Yuki KAWAI,* Masaharu MURATA,** Masahiko HASHIMOTO,* and Kazuhiko TSUKAGOSHI*,***

*Department of Chemical Engineering and Materials Science, Doshisha University, Kyotanabe 610-0321, Japan
**Department of Advanced Medical Initiatives, Kyushu University, Fukuoka 812-8582, Japan
***Tube Radial Distribution Phenomenon Recearch Center, Doshisha University, Kyotanabe 610-0321, Japan

The tube radial distribution of solvents was observed in an aqueous ionic liquid mixed solution of 1-butyl-3-methylimidazolium chloride fed into a capillary tube. A phase diagram was constructed with 1-butyl-3-methylimidazolium chloride and potassium hydroxide, which included boundary curves between homogeneous and heterogeneous solutions at 15 and 20°C. As an example, an aqueous ionic liquid mixed homogeneous solution, comprising the ratio of 1-butyl-3-methylimidazolium chloride:potassium hydroxide (30.5:16.5 wt/wt%), which were positioned near the boundary at 20°C, were delivered into a fused-silica capillary tube (75 μm i.d., 110 cm length, 15°C tube temperature) at a flow rate of 1.0 μL min⁻¹. The homogeneous solution changed to a heterogeneous solution with two phases: the inner (the aqueous phase merely containing the ionic liquid) and the outer (the ionic liquid-rich) phases, in the capillary tube. The radial distribution of the solvents in the aqueous ionic liquid mixed solution was observed through a bright-light microscope-CCD camera system.

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