Gradient counterflow electrophoresis methods for bioanalysis

CE has evolved as one of the most efficient separation techniques for a wide range of analytes, from small molecules to large proteins. Modern microdevices facilitate integration of multiple sample-handling steps, from preparation to separation and detection, and often rely on CE for separations. However, CE frequently requires complex geometries for performing sample injections and maintaining zone profiles across long separation lengths in microdevices. Two novel methods for performing electrophoretic separations, gradient elution moving boundary electrophoresis (GEMBE) and gradient elution isotachophoresis (GEITP), have been developed to simplify microcolumn operations. Both techniques use variable hydrodynamic counterflow and continuous sample injection to perform analyses in short, simple microcolumns. These properties result in instruments and microdevices that have minimal 'real-world' interfaces and reduced footprints. Additionally, GEITP is a rapid enrichment technique that addresses sensitivity issues in CE and microchips.