Electron capture ionization

Electron capture ionization is the ionization of a gas phase atom or molecule by attachment of an electron to create an ion of the form A–•. The reaction is

A + e^- \overset{M}{\to} A^-

where the M over the arrow denotes that to conserve energy and momentum a third body is required (the molecularity of the reaction is three).

Electron capture can be used in conjunction with chemical ionization.[1]

Electron-capture mass spectrometry

Electron-capture mass spectrometry is a type of mass spectrometry that uses electron capture ionization to form negative ions from chemical compounds with positive electron affinities. The approach is particularly effective for electrophiles. In contrast to electron ionization, EC-MS uses low energy electrons in a gas discharge. The technique can be used with gas chromatography-mass spectrometry.[2]

The attachment of a low energy electron can give rise to two possible reactions for the compound, as shown below. Either the compound attaches an electron to form a radical anion,

AB + e^- \to AB^{-\bullet} ,

or the compound fragments, resulting in electron capture dissociation (ECD).[3] ECD forms an anion fragment and a radical fragment

AB + e^- \to A^{-} + B^{\bullet}.

Fragmentation in ECI has been studied by tandem mass spectrometry.[4]

Electron capture detector

An electron capture detector is used in some gas chromatography systems.[5]

See also

Electron capture dissociation

References

  1. ↑ Donald F. Hunt; Frank W. Crow (1978), "Electron capture negative ion chemical ionization mass spectrometry", Analytical Chemistry 50 (13): 1781, doi:10.1021/ac50035a017
  2. ↑ Leis HJ, Fauler G, Rechberger GN, Windischhofer W (June 2004). "Electron-capture mass spectrometry: a powerful tool in biomedical trace level analysis". Curr. Med. Chem. 11 (12): 1585–94. doi:10.2174/0929867043365035. PMID 15180565.
  3. ↑ Giese, RW (2000). "Electron–capture mass spectrometry: recent advances". Journal of Chromatography 892 (1-2): 329–346. doi:10.1016/S0021-9673(00)00364-2. PMID 11045497.
  4. ↑ Wei J, Liu S, Fedoreyev SA, Voinov VG (2000). "A study of resonance electron capture ionization on a quadrupole tandem mass spectrometer". Rapid Commun. Mass Spectrom. 14 (18): 1689–94. doi:10.1002/1097-0231(20000930)14:18<1689::AID-RCM75>3.0.CO;2-G. PMID 10962492.
  5. ↑ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "electron capture detector (in gas chromatography)".
This article is issued from Wikipedia - version of the Tuesday, February 02, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.