ionization and proton transfer
Posted: Thu Sep 09, 2004 2:57 pm
by Sofia
I have a question about the ionization in ES; the theory seems to be that from the formed droplets ions evaporate (IEM) or are "left over" when the solvent evaporates (CRM). But then I read about proton transfer in the gas phase I became confused; is this still another kind of ionization process or is it just the protonated/deprotonated ions that undergo this process, while adducts (Like [M+NH4]+) are formed in the droplet and then released?
Please make it clearer to me!
Posted: Thu Sep 09, 2004 3:29 pm
by Kostas Petritis
Sofia,
These are two different ionisation techniques, electrospray ionisation (ESI) and athmospheric pressure chemical ionisation (APCI).
In ESI you have formation of charged droplets, followed by coulomb explosions which liberates the ions of interest.
In APCI you use the corona discharge to ionise your solvent ions in the gas phase and then with a complex series of reactions you donate/tranfer protons to your analytes.
Kostas
Posted: Fri Sep 10, 2004 10:45 am
by Sofia
Kostas,
Thank you for your reply, but I meant proton transfer in ES. I got confused when I read the article found at
http://www.spectroscopynow.com/Spy/pdfs/JMS35784.pdf
but now I´ve read it again and maybe my question was to quick; it seems like proton transfer may be an effect in ES that modifies some ions, depending on their proton affinity in gas-phase. If I understood it right...