Novel microfabricated device for electrokinetically induced pressure flow and electrospray ionization mass spectrometry

A novel microchip device for electrospray ionization has been fabricated an d interfaced to a time-of-flight mass spectrometer. Fluid is electrokinetic ally transported through the chip to a fine fused-silica capillary inserted directly into a channel at the edge of the device. Electrospray is establi shed at the tip of the capillary, which assures a stable, efficient spray. The electric potential necessary for electrospray generation and the voltag e drop for electroosmotic pumping are supplied through an electrically perm eable glass membrane contacting the fluidic channel holding the capillary. The membrane is fabricated on the microchip using standard photolithographi c and wet chemical etching techniques. Performance relative to other microc hip electrospray sources has been evaluated and the device tested for poten tial use as a platform for on-line electrophoretic detection. Sensitivity w as found to be approximately three orders of magnitude better than spraying from the flat edge of the chip. The effect of the capillary on electroosmo tic flow was examined both experimentally and theoretically. (C) 2000 Elsev ier Science B.V. All rights reserved.