A new high-performance interface for capillary electrophoresis electrospray ionization mass spectrometry

A novel capillary electrophoresis electrospray ionization mass spectrometry (CE/ESI-MS) interface has been developed based upon an alternative means of establishing electrical contact at the CE capillary terminus. In this design, the terminus of the CE separation capillary and a short ESI emitter capillary are connected and sheathed by polysulphone micro-dialysis tubing. The electrical connection, to close the CE circuit and simultaneously establish the electrospray voltage, is provided outside the membrane via an electrode in a small liquid reservoir. In contrast to the sheath flow and liquid junction interfaces, the flow rate of liquid to the ESI source consists of the CE eluent and is not increased. The use of a 'micro-spray' type emitter produces a stable electrospray at the very low flow rates typical of CE, providing a highly sensitive, efficient interface. Post-separation acidification of analytes via the dialysis junction is also demonstrated.