Features of EI
- EI is the most widely used ionization mode in GC/MS analysis. Almost all commercial GCMS instruments equip this mode as standard ionization.
- EI causes much fragmentation of a molecule whose spectral pattern is useful for identifying sample compound.
- Library search is available. EI mass spectra obtained by 70eV electron bombardment can be used for identification by comparing with spectra registered in the mass spectral library.
- An open type of ion source is used. Vacuum pressure inside the source, mainly determined by carrier gas, is about less than 10-2 Pa.
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