Generating electrospray from solutions predeposited on a copper wire

This study presents a novel direct probe (DP) to perform electrospray ioniz ation (ESI). The probe is constructed simply from a thin copper ring connec ted to a high voltage power supply, and a capillary and syringe pump are un necessary. Approximately one microliter of the sample solution is applied d irectly onto the copper ring by a micropipette, Electrospray from the solut ion on the copper ring is induced by surface deformation by deflecting a dr oplet from the copper ring. The mass spectra of proteins obtained by DP-ESI are exactly the same as those from conventional ESI sources through a capi llary needle, The time deemed necessary to complete an analysis is approxim ately 2 minutes, and sample switching is immediate. The signals of the anal yte can last from 45 seconds to more than 10 minutes depending on probe des ign, Three different types of probes used to retain more sample solution on the probe during electrospray were designed and constructed. Moreover, cle aning the probe between different sample analysis is easy. Since a capillar y is not used for sample transportation, presence of the particles in the s ample solution does not interfere with the electrospray process by capillar y blockage. Copyright (C) 1999 John Wiley & Sons, Ltd.