Ultra-fast two-dimensional microchip electrophoresis using SDS μ-CGE and microemulsion electrokinetic chromatography for protein separations

A poly(methyl methacrylate) microfluidic chip was used to perform a two-dimensional (2-D) separation of a complex protein mixture in short development times. The separation was performed by combining sodium dodecyl sulfate micro-capillary gel electrophoresis (SDS μ-CGE) with microemulsion electrokinetic chromatography (μ-MEEKC), which were used for the first and second dimensions, respectively. Fluorescently labeled Escherichia coli cytosolic proteins were profiled by this 2-D approach with the results compared to a similar 2-D separation using SDS μ-CGE∈×∈μ-MEKC (micelle electrokinetic chromatography). The relatively short column lengths (effective length∈=∈10 mm) for both dimensions were used to achieve separations requiring only 220 s of development time. High spot production rates (131∈±∈11 spots min^-1) and reasonable peak capacities (481∈±∈18) were generated despite the fact that short columns were used. In addition, the use of μ-MEEKC in the second dimension was found to produce higher peak capacities compared to μ-MEKC (481∈±∈18 for μ-MEEKC and 332∈±∈17 for μ-MEKC) due to the higher plate numbers associated with μ-MEEKC.