Ramsey Research GroupThe University of North Carolina at Chapel Hill

Department of Chemistry

Microchip ESI Basics

The basic operating principle of our CE-ESI is based on an electroosmotic pump. Figure 1 on the left shows a schematic of a typical CE-ESI microchip with a cross channel design (red channels) for performing sample injection and separation and a pump channel (E, black). The side channel is left uncoated (black) while all other channels (red) are coated with an amine to reverse the surface charge. The EOF in both the separation channel and the side channel flows toward the ESI orifice, generating pressure that drives the liquid out of the chip. An ESI voltage of ∼3.5-kV generates stable and sensitive electrospray. The amine coating repels peptides and proteins in acidic buffers allowing for highly efficient electrophoretic separations. Figure 2 on the right shows an image of the laser-illuminated ESI plume from the corner of the glass microchip.

ESI microchipESI plume