Posted by: tvasailor | April 24, 2022

Chemical Ionization GC-MS Substituting Liquid Reagents for Gasses

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Solvent Mediated Chemical Ionization (SMCI), as demonstrated by Shimadzu in a poster session, can be a very convenient means for substituting liquids as chemical ionization reagents for GC-MS. Gases in lecture bottles are often inconvenient to purchase, somewhat hazardous to use, and often very difficult to dispose of when spent. NOTE: Ammonia gas if not used properly can be delivered to the MS source as a liquid (see link: Ammonia Gas Connection on 1st page) !

SMCI using propylamine was shown by Eastman Chemical in their recent work to be very useful in the ionization of Surfynol. This compound is very difficult to ionize with many gasses showing the loss of water and no molecular weight information. The propylamine was found to offer similar useful molecular weight information which normally required the use of either ammonia and methylamine as shown in previous work at Eastman.

Other possibilities to try would be solutions of methylamine and ammonia in methanol that can be purchased from Aldrich, methanol-d4, ammonium hydroxide, deuterium oxide, propylamine in methanol-d4, etc. Of course, one could also do negative ion chemical ionization with a variety of solvents to get M-H or chloride adducts. The possibilities are somewhat endless depending on the class of compounds and their relative proton affinities using either pure solvents or mixtures taking into account their relative proton affinities.

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