Preconcentration electrokinetic mode

Capillary electrophoresis (CE) coupled to MS has the advantage of high resolution and soft ionization for biomolecules, which may be used to differentiate post-translational modifications and variants of intact proteins and oligonucleotides. Different modes of CE (capillary zone electrophoresis, capillary isoelectric focusing, capillary electrochromatography, micellar electrokinetic chromatography, nonaqueous capillary electrophoresis) to MS as well as online preconcentration techniques (transient capillary isotachophoresis, solid-phase extraction, membrane preconcentration) are used to compensate for the restricted detection sensitivity of the CE methodology [77, 78]. 

In much the same way that standard gel electrophoretic techniques diversified, so did CE. This has resulted in a family of specialized modes that collectively constitute CE. The main modes of CE that have been developed and are presently being exploited include capillary zone electrophoresis (CZE), MEKC, capillary electrokinetic chromatography capillary (CEC), capillary isoelectric focusing (CIEF), capillary gel electrophoresis (CGE), and capillary isotachophoresis (CITP). Over the last decade or so, this latter mode has been primarily used as an on-capillary preconcentration technique. 

On-column preconcentration procedures The word stacking defines any on-capillary mode of concentration or focusing analytes based on changes of electrophoretic velocity due to the electric field across concentration boundaries. Sample stacking can be performed in both hydrodynamic (e.g., gravity or pressure) and electrokinetic (e.g., voltages) injection modes. The sample solution is sandwiched between two portions of the CE separation buffer. When high... 

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