Agilent Technologies 5975 Operation Manual page 189

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Chemical Ionization Theory
Ion-molecule reactions
Ion-molecule reactions occur when oxygen, water, and other contaminants are
present in the CI ion source. Ion-molecule reactions are two to four times
slower than electron-attachment reactions and do not provide the high
sensitivity associated with electron capture reactions. Ion-molecule reactions
can be described by the general equation:
 MX
– –
M + X
–
where X is most often a halogen or hydroxyl group that was created by
ionization of contaminants by electrons from the filament. Ion-molecule
reactions compete with electron capture reactions. The more ion-molecule
reactions that occur, the fewer electron capture reactions occur.
5975 Series MSD Operation Manual for MassHunter 189