Tube Radial Distribution Phenomenon of Ternary Mixed Solvents in a Microspace under Laminar Flow Conditions

Abstract

When ternary mixed solutions of water-hydrophilic/hydrophobic organic solvents are fed into a microspace under laminar flow conditions, the solvent molecules are radially distributed in the microspace. The specific fluidic behavior of the solvents is termed "tube radial distribution phenomenon" (TRDP). In this study, water-acetonitrile-ethyl acetate mixed solutions (3:8:4 volume ratio) containing fluorescent dyes, perylene (0.1 mM) and Eosin Y (1 mM), were fed into fused-silica capillary tubes (75 μm i.d.) for investigating the TRDP with a fluorescence microscope-CCD camera under various analytical conditions. The pressure at the observation point for the fluorescence on the tube was changed by altering the flow rates, capillary total lengths, and capillary effective lengths. The obtained fluorescence images showed that the TRDP in the capillary tube created the inner and outer phases, i.e., the organic solvent-rich major inner and the water-rich minor outer phases in this case, providing the kinetic liquid-liquid interface. The formation of the inner and outer phases in the capillary tube was observed at flow rates of 0.5 -2.0 μL min -1 under the present analytical conditions. We also discuss the specific formation locations of the major and minor solvents.

Consideration of the Tube Radial Distribution of the Carrier Solvents in a Capillary Tube under Laminar Flow Conditions and Computer Simulation

“…13 In this paper, the formation of inner and outer phases in the TRDP is considered based on experimental data that were reported in our previous papers. [7][8][9][10] Also, the results of computer simulations agree well with the phase formation observed through the TRDP.…”

“…9 The linear velocity in the radial face section of the capillary tube (circle curves) under laminar flow conditions indicates that the inside area of a tube has a lower velocity-change gradient than the outside area. The real velocity curve in an aqueous-organic solvent mixed solution may deviate from an ideal velocity curve.…”

“…5,6 Recently, it was reported that, when a ternary solvent mixture of water-hydrophilic/hydrophobic organic solvent is fed into a microspace under laminar flow conditions, the mixture solvents are radially distributed in the microspace. [7][8][9] The radial distribution of the solvents in a microspace is referred to as the tube radial distribution phenomenon (TRDP) for convenience.…”

A Microflow-Extraction System Using Double Tubes Having Different Inner Diameters in Tube Radial Distribution Phenomenon

“…This is called the "tube radial distribution phenomenon" (TRDP) [8][9][10][11]. For example, in the TRDP with a non-ionic surfactant aqueous solution, through the two-phase separation property, a surfactant-rich phase is formed around the center of the microspace as an inner phase, while the aqueous, or almost surfactant-free, phase is formed near the inner wall as an outer phase [12].…”

Two-Phase Extraction of Metal Ions Using a Water-Acetonitrile-Ethyl Acetate Ternary Mixed-Solvent Separation System

“…[15][16][17] A novel two-phase separation system involving ternary mixed solvents has been reported by our group. [18][19][20] A ternary mixed solvent solution of water-hydrophilic/hydrophobic solvents changes from a homogeneous (single-phase) to a heterogeneous (two-phase) system with temperature and/or pressure changes. This phenomenon causes a specific fluidic behavior in a microspace, such as a microchannel on a microchip or a capillary tube, leading to new types of open-tubular capillary chromatography 21 and microreactors.…”