Sample preconcentration field-amplified stacking

Whether the stacking technique is called field-amplified stacking, transient isotachophoresis, or sample self-stacking, the driving force in on-column sample preconcentration for charges species is the need to satisfy the initial KRF conditions. Under separation and sample matrix conditions where the KRF is difficult to determine, simply calculations such as flcut and a offer a rapid evaluation of conditions for optimal transient ITP. 

Gong, M. J., Wehmeyer, K. R., Limbach, R A., Arias, R, and Heineman, W. R., On-line sample preconcentration using field-amplified stacking injection in microchip capillary electrophoresis, Analytical Chemistry, 78, 3130-5131, 2006. 

Field-amplified sample stacking is a fairly widely applicable method of achieving increased sensitivity for capillary and on-chip assays in a scheme that is easily integrated with electrophoretic separation techniques [4,34-43]. FASS is typically used as a preconcentration step that occurs before the electrophoretic separation of analyte ions. 

Field-amplified sample stacking (FASS) is a preconcentration technique which is commonly used in CE. The technique was first mentioned by Mikkers et al. in 1979 and has been intensively studied by Burgi and Chien et al." In 1995, Jacobson and Ramsey reported the first FASS experiment on a microchip. 

Quirino and Terabe have also devised the sweeping concept, in which the sample itself has no additives or com-plexation reagents. These additives are added to the separation buffer. The analyte, the pseudostationary phase, or both should have electrophoretic velocities when an electric field is applied. The extent of preconcentration is dictated by the strength of the interaction between the analyte and the pseudophase. A mixed mode for further stacking is one in which the sample is concentrated first by field-amplified injection under non-miceUar conditions. The buffers are changed and the polarity is reversed to induce sweeping of... 

In an effort to build up a food LOG, preconcentration, separation, and AD, all of them integrated in a microchip, has also been proposed for the analysis of dyes in several food samples [35]. The microchip layout was comprised of three parallel channels. Two of them were for field-amplified sample stacking and the subsequent field-amplified sample injection steps, while the third one was reserved for the AD. The preconcentration method was used to analyze the dyes in several food samples (juice, traditional Korean alcohol, fish, noodles, and red pepper powders). 

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