
167
The practical advantages of low-pressure CI are:
No need for an expensive vacuum pumping system to handle the large
amounts of reagent gas
Low consumption of expensive high-purity reagent gas
Minimal contamination of the ion source
The potential of alternating EI and CI scans without the compromises in
spectral quality typically seen in high-pressure sources
Very good CI sensitivity in the full-scan mode
Liquid reagents are easily used
Recommended Reading
For more information about the theory of chemical ionization and the
interpretation of CI mass spectra, refer to Chemical Ionization Mass
Spectrometry by Alex G. Harrison, CRC Press, Boca Raton, Florida, 1983.
For a comparison of high-pressure and low-pressure CI in an ion trap, refer
to S.M. Boswell, R.E. Mather, and J.F.J. Todd, “Chemical Ionization in the
Ion Trap: a Comparative Study,” Int. J. Mass Spectrom. Ion. Proc. 99 (1990),
139-149.
For examples of liquid CI reagents, refer to:
G.F. Bauerle, Jr., B.J. Hall, N.V. Tran, and J.S. Bradbelt, “Ion-Molecule
Reactions of Oxygenated Chemical Ionization Reagents with Vincamine”, J.
Am. Soc. Mass Spectrom. 7 (1996), 250-260.
G. Moneti, et.al, “Acetonitrile as an Effective Reactant Species for Positive-
Ion Chemical Ionization of Hydrocarbons by Ion-Trap Mass Spectrometry”,
Rapid. Commun. in Mass Spectrom., 10 (1996), 167-170.
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