Counterflow isotachophoresis in a monolithic column

Abstract

This study describes stationary counterflow isotachophoresis (ITP) in a poly(acrylamide-co-N,N'-methylenebisacrylamide) monolithic column as a means for improving ITP processing capacity and reducing dispersion. The flow profile in the monolith was predicted using COMSOL's Brinkman Equation application mode, which revealed that the flow profile was mainly determined by monolith permeability. As monolith permeability decreases, the flow profile changes from a parabolic shape to a plug shape. An experimental monolithic column was prepared in a fused-silica capillary using an ultraviolet-initiated polymerization method. A monolithic column made from 8% (wt.) monomer was chosen for the stationary counterflow ITP experiments. Counterflow ITP in the monolithic column showed undistorted analyte zones with significantly reduced dispersion compared to the severe dispersion observed in an open capillary. Particularly, for r-phycoerythrin focused by counterflow ITP, its zone width in the monolithic column was only one-third that observed in an open capillary. These experiments demonstrate that stationary counterflow ITP in monoliths can be a robust and practical electrofocusing method.

Microfluidic isotachophoresis: A review

“…An opposing hydrodynamic flow, hydraulic or electroosmotic, to electromigration during ITP is another way to increase the effective channel length and thus to increase analyte concentrations. However, as mentioned previously, parabolic flow patterns can lead to significant dispersion . Breadmore used GENTRANS to simulate the use of an electroosmosis counterflow for stationary ITP and found significant improvements in sensitivity.…”

“…Hydrodynamic flows are often necessary when attempting stationary counterflow ITP. Liu and Ivory used COMSOL Multiphysics to describe stationary counterflow ITP in a 2D axially symmetric capillary and determined that molecules with a lower diffusivity had more severe dispersion than molecules with a higher diffusivity. Furthermore, dispersion due to flow effects could be reduced by the addition of a monolith or stationary phase to the capillary.…”

Focusing analytes from 50 μL into 500 pL: On-chip focusing from large sample volumes using isotachophoresis

“…Similarly, Liu et al . 15 showed that the use of porous structures in a capillary significantly reduces dispersion caused by counterflow in ITP. As shown in Fig.…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2014–2016)

“…Liu et al. reported the use of a monolithic column (AAM‐based) with counter‐flow ITP for protein detection . ITP dispersion using the monolith column was compared with counter‐flow ITP in an open channel, with the monolith showing 22‐fold less band broadening than the open channel.…”