Editing Electron ionization (section)

{{Short description|Ionization technique}}
{{Use American English|date = February 2019}}
[[File:Electron Ionization.svg|300px|thumb|Electron ionization]]

'''Electron ionization''' ('''EI''', formerly known as '''electron impact ionization'''<ref name="MärkDunn2013">{{cite book|author1=T.D. Märk|author2=G.H. Dunn|title=Electron Impact Ionization|url=https://books.google.com/books?id=twntCAAAQBAJ|date=29 June 2013|publisher=Springer Science & Business Media|isbn=978-3-7091-4028-4}}</ref> and '''electron bombardment ionization'''<ref name="Kaufman1965">{{cite book|author=Harold R. Kaufman|title=Performance Correlation for Electron-bombardment Ion Sources|url=https://books.google.com/books?id=wKNpxLQWsjYC|year=1965|publisher=National Aeronautics and Space Administration}}</ref>) is an ionization method in which energetic [[electron]]s interact with solid or gas phase atoms or molecules to produce [[ion]]s.<ref>{{GoldBookRef|title=electron ionization|file=E01999}}</ref> EI was one of the first [[ionization]] techniques developed for [[mass spectrometry]].<ref>{{cite journal|last1=Griffiths|first1=Jennifer|title=A Brief History of Mass Spectrometry|journal=Analytical Chemistry|volume=80|issue=15|year=2008|pages=5678–5683|issn=0003-2700|doi=10.1021/ac8013065|pmid=18671338|doi-access=free}}</ref> However, this method is still a popular ionization technique. This technique is considered a hard (high fragmentation) ionization method, since it uses highly energetic electrons to produce ions. This leads to extensive fragmentation, which can be helpful for structure determination of unknown compounds. EI is the most useful for organic compounds which have a [[Molecular mass|molecular weight]] below 600  amu. Also, several other thermally stable and [[Volatility (chemistry)|volatile]] compounds in solid, liquid and gas states can be detected with the use of this technique when coupled with various separation methods.<ref name=":0">{{Cite book|title=Fundamentals of Contemporary Mass Spectrometry - Dass - Wiley Online Library|last=Dass|first=Chhabil|s2cid=92883349|doi=10.1002/0470118490|year = 2007|isbn = 9780470118498}}</ref>