I have always known that differently from ESI, the APCI source produces the molecular ion, because the formation of ions depends on the glow discharge, differently from the ESI source, where the ion formation depends on the matrix.
However, i see signals that seems to arise from a doubly charged species. And I'm wandering if in APCI - LC - MS is possible to detect multicharged ions and in-source dimers, and adduct, and which are the condition of their formation.
Yes, all those things are possible, although they may happen less frequently than ESI. For example, dimers (multimers) appear if the sample is a little too concentrated. Adducts (sodium, potassium, and so forth) can still occur, too. It depends on the analyte.
Thank so much for your very useful and interesting answers. Noel W Davies yes, I called unproperly [M+H]+ as molecular ion. So you mean that if an analyte has more than one protonable centers, may undergo to a multiple protonation and give multicharged ions? how can APCI ionization produce adducts to sodium, ammonium, and so forth, if the ionisation process happens in the gas phase differently from ESI?
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