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carboxylic acid fragment pattern
Posted: Fri Mar 26, 2010 12:52 am
by jiang295
Hi ,
In positive mode, is it possible for carboxylic acid successive loss of 18amu and 30amu, which are assumed to be water and formaldehyde?
Thanks a lot.
Posted: Fri Mar 26, 2010 4:51 am
by Don_Hilton
Highly unlikely. Note the fragmenation desecibed on the website:
http://www.chemistry.ccsu.edu/glagovich ... /acid.html
Once the radical ion forms, it will rearrange to separate the charge and radical and to provide a more stable ion. If fragmetnation creates intact moecules, they must be formed by rational movement of atoms and electrons.
Posted: Fri Mar 26, 2010 5:21 am
by jiang295
sorry, i forgot to mention it is in positive ESI mode.
sorry about that.
thanks for your reply.
Highly unlikely. Note the fragmenation desecibed on the website:
http://www.chemistry.ccsu.edu/glagovich ... /acid.html
Once the radical ion forms, it will rearrange to separate the charge and radical and to provide a more stable ion. If fragmetnation creates intact moecules, they must be formed by rational movement of atoms and electrons.
Posted: Fri Mar 26, 2010 11:15 am
by Don_Hilton
Once an ion is formed, the fragmentation pantways are similar. There is no good way to move two hydrogen atoms to the carbonyl to form formaldehyde. And with ESI you typically have less fragmentation and for many compunds see only the molecuar ion or an adduct.
Posted: Mon Mar 29, 2010 4:49 pm
by lmh
In my hands, carboxylic acid groups usually fragment by loss of 44 (CO2), or occasionally 46 (HCOOH) but of course in ESI every molecule is a law of its own.