SESI and ESI (Electro-Spary Ionization) have been linked since the initial development of ESI. Fenn and colleagues already noted that gas-phase species in the counterflow gas were also ionized by the spray. Still today, the routine calibration of mass spectral data relies on ubiquitous plasticizes and other contaminants (i.e. polydimethylcyclosiloxanes, phthalates) that are ionized in regular ESI via Secondary Electrospray Ionization mechanisms.
The ETH Zurich (Switzerland) has recently completed the acquisition and installation process of a new SUPER SESI unit for a Thermo Fisher Scientific Orbitrap mass spectrometer, that will help in different fields of the research conducted at this institution related to metabolomic studies.
Rising the humidity level of the gas introduced through the sample line accelerates the charge transfer reaction rate in Secondary Electrospray Ionization (SESI). It is hypothesized that larger clusters transfer their charge more efficiently than smaller clusters or even bare ions.