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

Abstract

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 mu-CGE) with microemulsion electrokinetic chromatography (mu-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 mu-CGE x mu-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 mu-MEEKC in the second dimension was found to produce higher peak capacities compared to mu-MEKC (481 +/- 18 for mu-MEEKC and 332 +/- 17 for mu-MEKC) due to the higher plate numbers associated with mu-MEEKC.