There is provided an electrical contact for a CE-MS interface. The contact is obtained by establishing a fracture or crack less than 2 micrometer in dimension(width) close to the spray tip. A reservoir is provided in liquid contact with the crack/fracture and filled with a reservoir liquid, and an electrode is placed in contact with the reservoir liquid. Several cracks/fractures can be created with their respective reservoirs. Beside providing the electrical contact for the electrophoretic separation and/or electrospray ionization, the crack/fracture can be used for electrokinetically introducing reagents or analytes into the capillary, for example, for providing deuterium for hydrogen-deuterium exchange (HDX) experiments.