Electron capture ionization: Difference between revisions

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[[electron capture negative ionization]]
 
deprecated:  [[electron attachment ionization]]
 
Ionization of a gas phase atom or molecule by attachment of a free electron to form M????????????????????? ions.
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#H. K. Lim, D. Andrenyak, P. Francom, R. L. Foltz, R. T. Jones. Anal. Chem. 60, 1420-1425 (1988).
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{{asms|
{{asms|
Resonance electron capture of thermal electrons - Should be referred to as "electron capture ionization" or "ECI".  The processes which ECI describes (Chemical Ionization Mass Spectrometry, Harrison, 2nd ed., 1992, p. 24-25):
Resonance electron capture of thermal electrons - Should be referred to as "electron capture ionization" or "ECI".  The processes which ECI describes (Chemical Ionization Mass Spectrometry, Harrison, 2nd ed., 1992, p. 24-25):


                    1)          MX + e-  ?  MX-                electron capture
:1)          MX + e-  ?  MX-                electron capture


                    2)          MX + e-  ?  M. + X-          dissociative electron capture
:2)          MX + e-  ?  M. + X-          dissociative electron capture


        Case (1) leads to formation and detection of a molecular anion, while case (2) leads to detection of a fragment with loss of a radical, for example, pentafluorobenzyl ester fragmentation.  
Case (1) leads to formation and detection of a molecular anion, while case (2) leads to detection of a fragment with loss of a radical, for example, pentafluorobenzyl ester fragmentation.  
   
   


{ Note from submittor:  Whether or not ECI/MS is acceptable to the committee, I hope that some consensus can be reached to describe the two processes I have described above.  I have seen them described as NCI, NICI, ECCI, ECNI and ECNICI.  I think its time to pick one.  By the way, my second choice would be ECNI (electron capture negative ion).}
{ Note from submittor:  Whether or not ECI/MS is acceptable to the committee, I hope that some consensus can be reached to describe the two processes I have described above.  I have seen them described as NCI, NICI, ECCI, ECNI and ECNICI.  I think its time to pick one.  By the way, my second choice would be ECNI (electron capture negative ion).}
   
   
The term ECI should be separate from the "chemical ionization" section of nomenclature and the term "electron attachment" should be dropped or changed to "electron capture" to avoid confusion.  This description should be limited to only those processes which involve thermal electron capture as the principle mode of ionization.  Other negative ionization procedures which are the result of ion/molecule interactions, such as chloride attachment, should still be referred to as negative ion chemical ionization.  Under electron capture conditions, the description of the "reagent" gas should be changed to "moderating gas" or "buffer gas".  As the gas is not acting as a reagent, these terms should be more description of the process involved.
The term ECI should be separate from the "chemical ionization" section of nomenclature and the term "electron attachment" should be dropped or changed to "electron capture" to avoid confusion.  This description should be limited to only those processes which involve thermal electron capture as the principle mode of ionization.  Other negative ionization procedures which are the result of ion/molecule interactions, such as chloride attachment, should still be referred to as negative ion chemical ionization.  Under electron capture conditions, the description of the "reagent" gas should be changed to "moderating gas" or "buffer gas".  As the gas is not acting as a reagent, these terms should be more description of the process involved.
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Revision as of 21:35, 30 May 2010


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ASMS TERMS AND DEFINITIONS POSTER ENTRY
Electron capture ionization

Resonance electron capture of thermal electrons - Should be referred to as "electron capture ionization" or "ECI". The processes which ECI describes (Chemical Ionization Mass Spectrometry, Harrison, 2nd ed., 1992, p. 24-25):

1) MX + e-  ? MX- electron capture
2) MX + e-  ? M. + X- dissociative electron capture

Case (1) leads to formation and detection of a molecular anion, while case (2) leads to detection of a fragment with loss of a radical, for example, pentafluorobenzyl ester fragmentation.


{ Note from submittor: Whether or not ECI/MS is acceptable to the committee, I hope that some consensus can be reached to describe the two processes I have described above. I have seen them described as NCI, NICI, ECCI, ECNI and ECNICI. I think its time to pick one. By the way, my second choice would be ECNI (electron capture negative ion).}

The term ECI should be separate from the "chemical ionization" section of nomenclature and the term "electron attachment" should be dropped or changed to "electron capture" to avoid confusion. This description should be limited to only those processes which involve thermal electron capture as the principle mode of ionization. Other negative ionization procedures which are the result of ion/molecule interactions, such as chloride attachment, should still be referred to as negative ion chemical ionization. Under electron capture conditions, the description of the "reagent" gas should be changed to "moderating gas" or "buffer gas". As the gas is not acting as a reagent, these terms should be more description of the process involved.

ASMS Terms and Definitions Poster
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