[en] An apparatus and method for separating materials, particularly isotopes of heavy metals is described. An electrohydrodynamic source of positive ions directed in a beam to a transverse magnetic field which deflects the ions along paths which carry the different mass ions to different collectors is included. An ion source incorporating a container for molten material, a pressure system for delivering the liquid material to a capillary tube, and a high voltage power supply providing an intense electrostatic field at the tube end for producing ions by field emission complete the apparatus