Chemical Ionization Mass Spectrometry

This experiment was developed by S.E. Van Bramer for Chemistry 465 at Widener University.


Chemical Ionization (CI) is a very useful technique. Because CI is much less energetic than electron ionization, CI does not induce as much fragmentation. This is very useful for identifying the molecular ion and determining the molecular weight of a compound. In this experiment we will use methane CI to study 1-propanol (C3H7OH), methyl ethyl ether (CH3OC2H5), 1-decanol (n-C10H21OH), tributyl amine ((n-C4H9)3N), and hexadecane (n-C16H34). This experiment is based upon Munson, M.S.B.; Field, F.H. J. Am. Chem. Soc., 1966, 88, 2621-2630. Chemical Ionization Mass Spectrometry. I. General Introduction.


  1. Overview of the instrument. Introduction to chemical ionization controls.

  2. Calibrate mass spectrometer.

  3. Data to collect. For each compound
    1. EI spectra. Collect 70 eV EI and 20 eV EI spectra for each compound.
    2. CI spectra. Collect CH4 CI spectra for each compound with a source pressure of:
      1. 0.05 torr
      2. 0.10 torr
      3. 0.15 torr
      4. 0.20 torr
      5. 0.25 torr

Laboratory Write-up:

Your Laboratory write-up should include the following information
  1. (10 pts) An abstract for this experiment.

  2. (10 pts) The Carbon pages from your laboratory manual.

  3. (10 pts) Clearly labeled spectra that show the EI and CI mass spectra for each compound.

  4. (20 pts) Analysis of your data
    1. Interpret the EI and CI mass spectra of each compound.
    2. Compare the EI and CI mass spectra.
    3. Determine how the source region pressure effects the CI spectra.

This page is maintained by
Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013

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Last Updated Thursday, September 02, 1999 12:54:22 PM