High sensitivity electrospray interface

The invention provides a sheath-flow interface for producing electrospray from a capillary. The electrospray generated by the interface can be used as the source of ions for mass spectrometry. Electrokinetic flow in the interface can move a sheath liquid past the end of a capillary so as to mix with an analyte effluent discharged from the capillary. The sheath liquid and analyte mixture can be directed to an electrospray emitter to generate an electrospray.