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A new etectrospray ionization Interface for capillary zone electrophoresis-mass spectrometry (CZE-MS) is described. The interface uses a sheath flow of liquid to make the electrical contact at the CZE terminus, thus defining both the CZE and electrospray field gradients. This allows the composition of the eiectrosprayed liquid to be controlled independently of the CZE buffer, providing operation with buffers that could not be used previously (eg, aqueous and high ionic strength buffers). The interface operation is independent of CZE flow rate; CZE capillaries are easily replaced and require no ad-ditional preparation. Since the electrospray occurs directly from the CZE capillary terminus, additional mixing volumes and metal surfaces are avoided and electrophoretic separa-tion efficiency appears unperturbed. The dead volume asso-ciated with the electrospray interface is< 10 nL, corre-sponding to< 0.1 s for typical flow …