A new electrospray-ionization time-of-flight mass spectrometer with electrostatic wire ion guide

The structure and performance of a time-of-flight (TOF) electrospray-ionization mass spectrometer with new features are described which are intended to give more control of the electrospray droplet desolvation process and to produce an analyte ion beam with low divergence. Free jet expansion of the carrier gas from the electrospray ion source produces a high energy beam of electrospray droplets with low divergence, which is desolvated under conditions where the pressure and temperature are well defined and controlled. The analyte ions formed retain the low divergence features of the parent electrospray droplets. The ions are transported to an orthogonal acceleration TOF analyzer using an electrostatic wire ion guide operating at low pressure. Excellent efficiency of transport to the orthogonal acceleration region is achieved with this configuration. Using the parameters of the instrument, SIMION trajectory calculations predict a maximum transport efficiency for a specific electrostatic ion guide (EIG) voltage which matches the experimental observations. Examples of the application of the system include a study of mass accuracy, thermally induced dissociation, and the study of ion-molecular collisions in the EIG region. (C) 1997 Elsevier Science B.V.