Counter-pressure-assisted ITP with electrokinetic injection under field-amplified conditions for bacterial analysis

Abstract

Counter-pressure was used to extend the duration of field-amplified sample injection in isotachophoresis (FASI-ITP) in order to improve the detection of bacterial cells. Using 0.51-μm negatively charged encapsulated fluorescent beads as a model, the counter-pressure, injection and separation voltages, and times were optimized. Using 6-min 8,963-Pa counter-pressure FASI-ITP injections at -12 kV followed by mobilization of the ITP band with continued injection at -6 kV, the limit of detection (LOD) for Escherichia coli was improved to 78 cells/mL, a factor of 4 when compared with FASI-ITP without counter-pressure.

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016–2018)

“…Another limitation of the electrokinetic injection of sample is the movement of the stacking boundary during the long FASI step. Many approaches in the last 10 years were proposed for the immobilization of the stacking boundary through application of a counterflow (CF‐EKS) or employing the EOF to cease the movement of the stacking boundary . Recently, the Chung's group revisited CF‐EKS for the sensitive speciation of arsenic in water samples .…”

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

“…Breadmore et al. reinvestigated the application of a hydrodynamic counterflow in order to immobilize the stacking boundary for enrichment of bacterial cells. After filling the capillary with the LE (50 mM Tris‐HCl, pH 8.0 with 0.5% w/v of PVP), the counter pressure was employed during EKI of the sample.…”

“…Phung et al. introduced a counter‐flow EKI for cells to prolong the enhanced field and enhance detection limits . Using LIF and staining the cells with a universal nucleic acid dye, E. coli could be detected down to 78 cells/mL, from a 100 μL volume of sample.…”

Analytical capillary isotachophoresis after 50 years of development: Recent progress 2014–2016

“…Phung et al. described the use of counter‐pressure‐assisted ITP (LE: HCl, 50 mM Tris, 0.5% w/v PVP, pH 8.0; TE: 5 mM HEPES, 5 mM Tris, pH 7.8; LIF detection) with electrokinetic injection for bacterial cell analysis. Using 6‐min counter‐pressure electrokinetic injections followed by mobilization of the ITP zone with continued injection, the LOD for E. coli was improved to 78 cells/mL, a factor of 4 when compared with injection without counter‐pressure.…”