ESI-MS via an electrokinetically pumped interface

An emitter for an electrospray ionization-mass spectrometer (ESI-MS) comprising:

• a hollow cylinder having an orifice at a distal end, wherein the inner diameter of the orifice is smaller than the inner diameter of the cylinder body and the surface of the emitter comprises a coating of one or more organic chemicals covalently bonded to the surface wherein the organic chemicals comprise one or more functional moieties;
• a separation capillary disposed inside the emitter;
• and
• a union to the emitter and an inlet for a sheath liquid;
• wherein the functional moieties are positively charged and the positively charged functional moieties stabilize the direction of electroosmotic flow (EOF) of the sheath liquid toward the orifice.

A method for adapting a glass emitter for a negative mode electrospray ionization-mass spectrometer (ESI-MS) comprising:

• covalently bonding organic chemicals having functional moieties to the surface of a glass emitter, wherein the glass emitter is a hollow cylinder comprising an orifice at a distal end and the inner diameter of the orifice is smaller than the inner diameter of the cylinder body;
• and
• interfacing the glass emitter and a separation capillary to a mass spectrometer, wherein a separation capillary is disposed inside the emitter;
• wherein a mixture of one or more analytes in a separation background electrolyte are separated in the capillary;
• wherein when a negative mode electrospray voltage is applied to a sheath liquid introduced to the emitter, positive charges form on the functional moieties to stabilize the direction of electroosmotic flow (EOF) of the sheath liquid toward the orifice, and the analytes exiting the capillary are transported toward the orifice by the EOF around the distal tip of the capillary, wherein an ionized electrospray is formed as the sheath liquid and the analytes exit the orifice.