A capillary and microchip-based nanoelectrospray emitter using a mesoporous membrane

A method is described for the fabrication of multipath electrospray emitters using hydrophobic porous polymer membranes. Polysulphone (PSF) and polycarbonate (PC) membranes, which possess pores with well-defined sizes, are glued onto the exit aperture of fused-silica capillaries or microfluidic chips to create multipaths to assist electrospray at moderate nano flow rates (e.g., 50–500 nL/min). A capillary-based multipath emitter fabricated with either PSF or PC membranes was prepared with a fused-silica capillary with 75 µm inner diameter and 360 µm outer diameter. Relative effects on electrospray performance at different flow rates, electrospray voltages, and solvent compositions are probed. The sensitivity and stability of electrospray signals were enhanced through spraying from multiple pores on the membrane. An embossed polycarbonate microchip was also interfaced to the mass spectrometer using the meso porous membrane approach.Key words: nanoelectrospray, membrane, emitter, multipaths, microchip.