Elastomeric microchip electrospray emitter for stable cone-jet mode operation in the nanoflow regime.
Despite widespread interest in combining laboratory-on-a-chip technologies with mass spectrometry (MS)-based analyses, the coupling of microfluidics to electrospray ionization (ESI)-MS remains challenging. We report a robust, integrated poly(dimethylsiloxane) microchip interface for ESI-MS using simple and widely accessible microfabrication procedures. The interface uses an auxiliary channel to provide electrical contact for the stable cone-jet electrospray without sample loss or dilution. The electric field at the channel terminus is enhanced by two vertical cuts that cause the interface to taper to a line rather than to a point, and the formation of a small Taylor cone at the channel exit ensures subnanoliter postcolumn dead volumes. Cone-jet mode electrospray was demonstrated for up to 90% aqueous solutions and for extended durations. Comparable ESI-MS sensitivities were achieved using both microchip and conventional fused silica capillary emitters, but stable cone-jet mode electrosprays could be established over a far broader range of flow rates (from 50-1000 nL/min) and applied potentials using the microchip emitters. This attribute of the microchip emitter should simplify electrospray optimization and make the stable electrospray more resistant to external perturbations.
Kelly
Ryan T
RT
Biological Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, USA.
Tang
Keqi
K
Irimia
Daniel
D
Toner
Mehmet
M
Smith
Richard D
RD
D004129:Dimethylpolysiloxanes; D044085:Microfluidics; D036103:Nanotechnology; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation*
D004129:Dimethylpolysiloxanes; C013830:baysilon