Free Flow Ion Concentration Polarization Focusing (FF-ICPF)

Abstract

Electrokinetic separation techniques in microfluidics are a powerful analytical chemistry tool, although an inherent limitation of microfluidics is their low sample throughput. In this article we report a free-flow variant of an electrokinetic focusing method, namely ion concentration polarization focusing (ICPF). The analytes flow continuously through the system via pressure driven flow while they separate and concentrate perpendicularly to the flow by ICPF. We demonstrate free flow ion concentration polarization focusing (FF-ICPF) in two operating modes, namely peak and plateau modes. Additionally, we showed the separation resolution could be improved by the use of an electrophoretic spacer. We report a concentration factor of 10 in human blood plasma in continuous flow at a flow rate of 15 μL min–1.

Out-of-plane faradaic ion concentration polarization: stable focusing of charged analytes at a three-dimensional porous electrode

“…13 Many existing ICP-based preconcentrators operate at > 100 V, which hinders integration into portable devices. Further, improvement of volumetric throughput, 2,14,15 integration with downstream analysis, [16][17][18][19] and the development of strategies to decrease fluidic instability are active areas of research. 20,21 Fluidic instability (evidenced by size and magnitudes of vortex flow near the electrode), which is caused by steep gradients in electrolyte concentration and electric field strength and exacerbated by increased device dimensions, leads to unwanted mixing, ultimately limiting sensitivity.…”

Numerical Simulation of Continuous Extraction of Li+ from High Mg2+/Li+ Ratio Brines Based on Free Flow Ion Concentration Polarization Microfluidic System

“…Similar to the device in [ 33 ], the microfluidic device we study is composed of a chamber surrounded by four microchannels arrays. Surfaces of the microchannels at the upper and lower sides of the chamber are positively charged.…”

“…In recent work, Papadimitridou et al reported a new system to focus (and separate) charged particles [ 33 ]. In their system, sample solutions were pumped horizontally from left to right (as in Figures of [ 33 ]) through a macroscale chamber, with all the chamber walls formed by large arrays of microchannels. In the meantime, an electric field was applied in the perpendicular direction (vertically from top to bottom as in Figures of [ 33 ]).…”

“…In their system, sample solutions were pumped horizontally from left to right (as in Figures of [ 33 ]) through a macroscale chamber, with all the chamber walls formed by large arrays of microchannels. In the meantime, an electric field was applied in the perpendicular direction (vertically from top to bottom as in Figures of [ 33 ]). Nafion membranes are embedded across the microchannel arrays outside the bottom boundary of the chamber to facilitate the cation-selective transport and generate the ICP effect there.…”

Droplet encapsulation of electrokinetically-focused analytes without loss of resolution

“…The extraction of analytes electrokinetically focused via ion concentration polarization focusing (ICPF) has been reported before by our group 1,2 and a number of other researchers. [3][4][5][6][7][8] Continuous extraction methods such as our previous work and the work 2 of Kwak et al 5 suffer from low preconcentration rates. On the other hand in non-continuous methods, after extraction a significant decrease in concentration and separation resolution inevitably occurs due to diffusion.…”