CE/MS combines the short analysis time and high separation efficiency of capillary electrophoresis (CE) with the molecular weight and structural information from the mass selective detector (MS). The technique has been successfully used for the analysis of various compounds in complex sample matrices. The Agilent Capillary Electrophoresis system can be interfaced directly to the Agilent 1100 Series mass selective detector with no positional adjustments and with full single-point control of CE and MS through an Agilent ChemStation. The electrospray ionization (ESI mode) of MS has proven to be sensitive, versatile and easy to use in combination with CE.