Miniature mass spectrometry (ESI-MASS SPECTROMETER) experiments were performed with a custom atmospheric interface and a differentially pumped vacuum system. A schematic of a typical experimental setup is shown in FIG. 1.
The microchip-ESI device (FIGS. 5A/5B CE or Infusion) was mounted on a custom x-y-z stage and positioned approximately 5-10 mm from the inlet capillary 15 (FIG. 1). A single sided copper clad circuit board (M.G. Chemicals, Burlington, Ontario, Canada) was used to shield the ESI orifice from the voltages applied to the reservoirs (not shown). The corner of the microfluidic devices extended about 5 mm through a slit in the board. The circuit board was held at +1 kV for CE experiments and GND for infusion experiments.
The microchip device shown in FIG. 5A for capillary electrophoresis and FIG. 5B for infusion, were glass microchips. The channels were etched to a depth of 10 μm. Reservoirs are designated with circles and indicate sample (S), background electrolyte (BG), sample waste (SW), and electroosmotic pump (P). For some of the experiments, the microchip had an injection cross, a 46-cm serpentine separation channel, and an electoosmotic pumping channel. The infusion device (5B) had of a 5.5-cm channel and an electoosmotic pumping channel, and both reservoirs are filled with the same sample.
