Counter-flow gradient electrofocusing.

Counter-flow gradient electrofocusing techniques are methods whereby a combination of electrophoresis and a bulk solution counter-flow is used to accumulate or focus analytes at stationary points along a separation column. This review first describes the various forms of counter-flow gradient electrofocusing that have been demonstrated in the literature and then compares figures of merit for counter-flow focusing methods and conventional CE methods. In an effort to compare the concentration enhancement of the various focusing techniques against each other, as well as of stacking methods, the parameter of analyte-accumulation velocity is introduced and employed to normalize the efficacy of the techniques.