Integration of a Microextraction System on a Glass Chip: Ion-Pair Solvent Extraction of Fe(II) with 4,7-Diphenyl-1,10-phenanthrolinedisulfonic Acid and Tri-n-octylmethylammonium Chloride

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Abstract
An ion-pair solvent extraction was performed in a microchannel fabricated in a quartz glass chip. The aqueous solution of Fe−bathophenanthrolinedisulfonic acid complex and the chloroform solution of tri-n-octylmethylammonium chloride were introduced into the microchannel, and a parallel two-phase laminar flow was formed. The ion-pair product extracted in chloroform was monitored by the thermal lens microscope. The ion-pair product was gradually extracted from aqueous solution into chloroform when the flow was very slow or stopped, while nothing was extracted into chloroform when the flow was fast. The time for extraction in the present 250 μm microchannel, 45 s, roughly coincided with the molecular diffusion time, and the extraction time was at least 1 order shorter compared with the ordinary extraction time using a separatory funnel and mechanical shaking. The microspace in the microchannel was characterized by the large specific interface area and short diffusion distance, and these characteristics may contribute to highly efficient extraction without mechanical shaking. The success of this molecular transport may lead to the integration of more complicated separation and chemical operations on a microchip and more applications.