Methane-ammonia chemical ionization

Figure 8 Typical fingerprint mass spectra for a peppermint oil obtained using an Agilent MS chemical sensor in three different modes (a) electron impact ionization, (b) positive chemical ionization with methane reagent gas, and (c) positive chemical ionization with ammonia reagent gas.

Three reagent gases are mainly used in positive chemical ionization methane, isobutane, and ammonia. Their proton affinities (in kilojoules per mol) are methane. 

What are the three commonly used chemical ionization reagent gases (methane, isobutane, water, ammonia, methanol, hydrogen, oxygen, nitrogen, etc.). 

Chemical ionization MS of 2-aryl-3-nitro-2//-chromenes and 4-hydroxy-3-nitroflavans have been studied using methane and ammonia as reagent gases102. The behaviour of 2-aryl-3-nitro-2//-chromenes was found to resemble that of aromatic nitro compounds. Thus, the methane spectra are characterized by the MH+ ions, whereas the ammonia... 

Chemical ionization produces less fragmentation than electron ionization. For chemical ionization, the ionization source is filled with a reagent gas such as methane, isobutane, or ammonia, at a pressure of 1 mbar. Energetic electrons (100-200 eV) convert CH4 into a variety of reactive products ... 

Another conventional ionization technique termed chemical ionization (Cl), utilizes a reagent gas (such as isobutane, methane, ammonia) to form reagent ions (Rif) which can undergo ion-molecule reactions with the compound of interest to form protonated molecules. 

We have found methane-ammonia chemical ionization to be well suited for the analysis of a wide variety of drugs (4). However, some compounds are ionized with poor efficiency under these Cl conditions, so it is important to measure the relative sensitivities afforded by different modes cf ionization before selecting a procedure for a given compound. 

Chemical ionization (Cl) On applying a beam of electrons to a biomolecule in the presence of a large excess of reagent gas (ammonia or methane), the biomolecule gains a proton (H+) and is thus ionized. 

Chemical ionization (Cl) mass spectra for 34 cholestane derivatives show correlations with structure. Methane, isobutane, and ammonia were used as... 

Most investigations of the chemical ionization (Cl) mass spectral behavior of saccharides have employed methane, isobutane, ammonia, helium (e capture), or a combination of these gases. The reacting forms of these gases are CHs", C Hg, and NH, which decrease in their protonating capability in the order shown. Thus, fragment ions are quite abundant in the methane and isobutane spectra of saccharides, whereas the ammonia Cl spectra are dominated by ammonia duster and sample adduct ions (72TL4827),... 

In chemical ionization, in addition to the carrier gas and the analytes coming from the GC, a reagent gas (methane, butane, ammonia, etc.) is injected in the ion source at a... 

Chemical ionization results from the gas-phase collision between the molecules of analyte M and the species obtained through the electron bombardment of a reagent gas, such as methane, ammonia or isobutene introduced concomitantly, at a pressure of a few hundred pascals, with the compound into the ion source of... 

Several gases are used in Cl ionization methane, propane, isobutane, hydrogen, ammonia, water, tetramethyl silane, or dimethyl amine. The Cl ion source is similar to the El source but is designed to have an ionization chamber. In positive chemical ionization, the ion source is filled with a reagent gas which is ionized to create a species of the proton donator type that can form a... 

Chemical Ionization (Cl) is a soft ionization technique that produces molecular ions (M" " or M ), adduct ions (M CI reagent), and fragment ions. Instrumentation is more expensive but Cl permits isomer differentiation. Cl reagents are usually methane, isobutane, or ammonia. The degree of fragmentation is less than in EL... 

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