A new electrospray emitter capable of cone-jet mode spray for liquid flow-rates from sub-microliter/minute to 10's of microliters/minute is provided. The high efficiency of ionization and vaporization enabled by the disclosed spray emitter provides improved sensitivity for mass spectrometer detection. The disclosed spray emitter sprays consistently and robustly a liquid buffer having a large range of compositions of aqueous and organic solvents, and is not sensitive to the polarity of the electric field used to induce spray. The fluidic channel leading to the spray emitter opening does not have an internal taper rendering the spray emitter clog-resistant.
