Ionization conditions and ion formation in electrohydrodynamic mass spectrometry

Track Membrane Mediated Electrostatic Introduction of Cluster Ions into TOF Mass Spectrometer

“…In EHDI applications 3 such ion transfer is stimulated by high-field conditions, which are known to develop at the tip of a fine metallic capillary. The liquid phase is in a highly unstable state there . Hence, the emission of charged species is stipulated and monitored by the instability itself.…”

“…The method utilizes high electrostatic field conditions applied to a multichannel network of a submicropore track membrane (TM). TM-mediated extraction of charged species should be distinguished from the traditional methods of electrohydrodynamic ionization (EHDI). − For one, in various EMIS applications the transport of charged species, as well as the field structure, is strongly due to a dense network of a large number of quite long (10−20 μm), yet very narrow (submicrometer), channels , present in TM. Moreover, a feedback charging of the vacuum facing side of TM is of prime importance in producing high local fields .…”

The solvent shells of cluster ions produced by direct electric field extraction from glycerol/water mixtures

“…In this model, in accordance with our experimental results, the distribution is independent of F . (Note that no dependence of the distribution on the voltage applied to the capillary was observed in EHDI investigations also 5…”

“…As was found earlier,4 under appropriate conditions ions can be released directly from the liquid. In the context of the electrostatic dispersion (spraying) of liquids, EHDI can be regarded as a limiting case of the conditions required to maximize the number of ions that can be extracted directly from a liquid 5. In the EHDI techniques normally practiced, the liquid sample, usually a solution of the analyte in glycerol, is dispersed from the tip of a metal capillary biased at a voltage of 7–10 kV relative to an electrode placed in the vacuum.…”

“…The actual ionization is a purely electrolytic dissociation process in solution, and the electric field extracts only those solvated ions that exist at the surface of the liquid. The model of field evaporation through an intact liquid surface, proposed previously6 for EHDI, has been criticized5 because the release of an ion from a liquid can only occur via electrohydrodynamic instability of the liquid surface stressed by an electric field 7. Optical investigations8,, 9 have shown that the ion emission in an EHDI process occurs in the so‐called ‘rim mode’, when ions are released from several discrete emission sites located along the rim of the capillary.…”