Minimizing analyte electrolysis in an electrospray emitter

The electrospray (ES) ion source is a controlled-current electrolytic now c ell. Electrolytic reactions in the ES emitter capillary are continually ong oing to sustain the production of charged droplets and ultimately gas-phase ions from this device. Under certain circumstances, the analytes under stu dy may be directly involved in these electrolytic processes. It is demonstr ated that a simple means to minimize analyte electrolysis is to exchange th e normal metal emitter capillary of commercial ES sources with one made of fused silica. This change is shown to provide an ES mass spectrometric syst em of similar performance in terms of gas-phase ion signal generated for no n-electroactive analytes and also assures minimal oxidation of electroactiv e analytes even at low (2.0 mul min(-1)) solution flow-rates and high (mill imolar) solution electrolyte concentrations.