A probe assembly is disclosed comprising an inlet for receiving an eluent from a chromatography device; an outlet (120) for delivering the eluent to an ion source of a mass spectrometer; and an attachment device (122) for attaching the outlet to the mass spectrometer. The outlet comprises an electrically conductive capillary (124) and an electrically conductive member (129) surrounding at least part of the electrically conductive capillary (124). The electrically conductive member (129) is arranged to receive a voltage upon connection of the attachment device (122) to the mass spectrometer and the electrically conductive member (129) is arranged to provide an electrical connection from the electrically conductive member (129) to the electrically conductive capillary (124).