Analytical Sciences

Spatially-Resolved Fluorescence Spectroscopic Study on Liquid/Liquid Extraction Processes in Polymer Microchannels

Haeng-Boo KIM,  Kousei UENO, Masahiro CHIBA, Osamu KOGI, and Noboru KITAMURA 

Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan

The liquid/liquid extraction of an Al³⁺-DHAB chelate (DHAB = 2,2'-dihydroxyazobenzen) from water to 1-buthanol (BuOH) in a polymer-based microchannel chip was studied by spatially-resolved fluorescence microspectroscopy. A microchannel (depth, 10 um; width, 200 um) was fabricated on a styrol-plastic substrate by an imprinting method. A template for imprinting was prepared by photolithography, in which a spatial pattern printed on a transparency film by a standard drawing software package was used as a photomask. When two immiscible fluids were brought together into the channel chip by pressure-driven flow at the same velocity, a stable parallel stream was observed for each phase without mutual mixing. The extraction of Al-DHAB from water to BuOH was then studied as a fluorescence-intensity profile of the complex in the BuOH phase along the flow direction as well as along the channel-width direction. It was confirmed that extraction proceeded with solution flow and was governed by the contact time between the two phases. The results were explained by a one-dimensional mass-transfer model along the channel-width direction.

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