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

Analytical and bioanalytical chemistry (2015-07-06)
Sui Ching Phung, Yi Heng Nai, Mirek Macka, Shane M Powell, Rosanne M Guijt, Michael C Breadmore
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.

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