Issue 14, 2015

Microscale extraction and phase separation using a porous capillary


We report the use of a porous polytetrafluoroethylene capillary for the inline separation of liquid–liquid segmented flows, based on the selective wetting and permeation of the porous capillary walls by one of the liquids. Insertion of a narrow flow restriction at the capillary outlet allows the back pressure to be tuned for multiple liquid–liquid combinations and flow conditions. In this way, efficient separation of aqueous–organic, aqueous–fluorous and organic–fluorous segmented flows can be readily achieved over a wide range of flow rates. The porous-capillary-separator enables the straightforward regeneration of a continuous flow from a segmented flow, and may be applied to various applications, including inline analysis, biphasic reactions, and purification. As a demonstration of the latter, we performed a simple inline aqueous–organic extraction of the pH indicator 2,6-dichloroindophenol. An aqueous solution of the conjugate base was mixed with hydrochloric acid in continuous flow to protonate the indicator and render it organic-soluble. The indicator was then extracted from the aqueous feed into chloroform using a segmented flow. The two liquids were finally separated inline using a porous PTFE capillary, with the aqueous phase emerging as a continuous stream from the separator outlet. UV-visible absorption spectroscopy showed the concentration of indicator in the outflowing aqueous phase to be less than one percent of its original value, confirming the efficacy of the extraction and separation process.

Graphical abstract: Microscale extraction and phase separation using a porous capillary

Article information

Article type
13 Apr 2015
19 May 2015
First published
09 Jun 2015
This article is Open Access
Creative Commons BY license

Lab Chip, 2015,15, 2960-2967

Author version available

Microscale extraction and phase separation using a porous capillary

T. W. Phillips, J. H. Bannock and J. C. deMello, Lab Chip, 2015, 15, 2960 DOI: 10.1039/C5LC00430F

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