Liquid junction apparatus for electrospray ionization

A liquid junction apparatus for electrospray ionization comprises an electrospray emitter 22, a capillary conduit assembly 30, and a union 36 to accommodate the electrospray emitter and the capillary conduit assembly to form a low dead volume butt joint which allows liquid to be transmitted from the capillary conduit assembly to the electrospray emitter. The entrance end of the electrospray emitter is encased or covered in a conductive sheath 28 (e.g. a metal tubing). The union 36 comprises an electrically conductive material and is connected to a voltage source 42. The conductive sheath is in electrical contact with the union so that liquid at the butt joint is maintained at a voltage to facilitate electrospraying. The butt joint may encompass a slight gap between the exit of the capillary conduit assembly and the entrance end of the electrospray emitter to facilitate electrical contact of the liquid with the conductive sheath. The union may comprise a slit extending along its length to facilitate lateral insertion and withdrawal of the electrospray emitter.