Samples submitted for ESI experiments must be dissolved in a suitable solvent (either Methamol or Acetonitrile or mixtures therof with water).
What happens to a sample is that a small amount of solution is drawn up into the probe tip and an electrically charged aerosol spray is produced in a stream of heated dry nitrogen gas. Solvent is evapourated from the small droplets of the spray and charged ions are ejected from the droplets. These ions are then drawn into the cone area at the front of the electrospray source and thence finally into the mass spectrometer proper.
Electrospray is a soft ionisation techniques. ESI Mass Spectra exhibit little signs of fragmentation when compared with those produced by the older Electron Impact (EI) technique. This makes it a good technique for molecular ion identification. Furthermore, depending on the solvent, adducts are often seen -
such as M + 23 = M + Na or M + 41 = M + CH3CN, to give but two examples.
The present m/z limit for ESI experiments is about 1300 daltons - however, this will improve once better calibration methods and samples become available!
Links to the rest of the Mass Spectrometry Service web pages are listed below for your convenience:-
Please contact Dr Georgina Rosair for further information.