This post includes information on the choice of amines as chemical ionization reagent gases and the building of a CI manifold. Also, see section in The Encyclopedia of Mass Spectrometry, Volume 4, Fundamentals of and Applications to Organic (and Organometallic) Compounds, Edited by M Gross et al, “Deuterated Ammonia Chemical Ionization: Use in Counting Exchangeable Hydrogen Sites on Organic Compounds,” p 772-780, D. M Parees, A. Z Kamzelski, J. L. Little, 2005
Ammonia is normally adequate for most applications. However, gas mixtures of other alkylamines with methane can yield less fragmentation data and resolve ambiguous ammonia CI data. Deuterated ammonia and alkyl amines can distinguish isomeric compounds in some cases.
Tips for Using CI Gasses:
http://www.littledomain.com/james/files/cigas.pdf
We use a wide variety of chemical ionization gases in our laboratory for the molecular weight determination of unknowns. In the link below, a versatile chemical ionization manifold is described that can be retrofitted to any commercial mass spectrometer. The paper includes plans for building it, operating it, and maintaining it.
Plans for Building Custom Manifold:
O manifolds supplied as by the manufacturer will not function properly. In many cases, it is due to the incompatibility of o-rings in the gas solenoids. We use a custom manifold on many of our GC-MS instruments. Here is some information on building and using the manifold:
http://www.littledomain.com/james/files/manifold.pdf
The most current interface is easier to build than the one described in the above PDF document. Here is a picture of the current interface which is utilized on our Thermo DSQ GC-MS:
