Analytical Sciences

Raman Microspectroscopy/Imaging Study on Phase-Vanishing Processes of Fluorous Biphase Systems in Microchannel-Microheater Chips

Takeshi ARAKI,* Kousei UENO,** Hiroaki MISAWA,** and Noboru KITAMURA*

*Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan
**Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0021, Japan

Temperature-dependent phase-vanishing processes between perfluorohexane (FC-72) and n-heptane (C₇H₁₆, volume ratio of 1:1 and phase-vanishing temperature > 41°C), were studied in a glass microchannel-microheater chip under solution-flow conditions. Without applying a voltage to the heater at 21°C, the two liquids in the microchannel were separated into two streams at a solution flow rate (v) of 0.975 cm/s, while the phase boundary between FC-72 and C₇H₁₆ vanished in the downstream side of the heater at V = 4.5 V. Then, we conducted Raman intensity imaging during the phase vanishing processes in the microchannel by monitoring the band at 756 (FC-72) or 1456 cm^-1 (C₇H₁₆). At V = 4.5 V and v = 0.975 cm/s, although no phase boundary between the two liquids in the microchannel was observed, the relevant Raman intensity images indicated the inhomogeneous nature of the solution, and distribution of C₇H₁₆ to the FC-72 phase along with solution flow was observed.

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