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Chemical ionization reagent gas

B. Benzene as a Selective Chemical Ionization Reagent Gas. Org. Mass Spectrom. 1990, 25,497-502. [Pg.352]

Membranes can be classified as porous and nonporous based on the structure or as flat sheet and hollow fiber based on the geometry. Membranes used in pervaporation and gas permeation are typically hydrophobic, nonporous silicone (polydimethylsiloxane or PDMS) membranes. Organic compounds in water dissolve into the membrane and get extracted, while the aqueous matrix passes unextracted. The use of mircoporous membrane (made of polypropylene, cellulose, or Teflon) in pervaporation has also been reported, but this membrane allows the passage of large quantities of water. Usually, water has to be removed before it enters the analytical instrument, except when it is used as a chemical ionization reagent gas in MS [50], It has been reported that permeation is faster across a composite membrane, which has a thin (e.g., 1 pm) siloxane film deposited on a layer of microporous polypropylene [61],... [Pg.215]

A Hewlett-Packard (Palo Alto, CA, USA) Model 5988A TSP LC-MS quadrupole mass spectrometer and a Hewlett-Packard Model 59970C instrument for data acquisition and processing were employed, The TSP temperatures were stem 100 fiC, tip 178 9C, vapour 194 C and ion source 296 aC with the filament on. In all the experiments the filament-on mode (ionization by an electron beam emitted from a heated filament) was used. In this mode of operation conventional positive and negative ohemioal ionization can be carried out by using the vaporised mobile phase as the chemical ionization reagent gas (4). [Pg.50]

Christopher, R. K. and Duffield, A. M. (1980) Use of vinyl methyl ether as a chemical ionization reagent gas for gas chromatographic chemical ionization mass spectrometric discrimination between cyclopropanoid and monoenoic fatty acid methyl esters. Biomed. Mass Spectrom., 1 (10), 429-32. [Pg.177]

Computer mass range up to m/z 1450. Ion source temperature, 250 C, accelerating voltage 3 kV, resolution M/dM 1000 (10% valley). The electron energy for El was 70 eV the Cl (chemical ionization) reagent gas was generally isobutane, but methane was also used. [Pg.256]

It appears that gas-phase basicity of nitro compounds has been studied only scarcely. Thus, only the values of the parent compounds, nitromethane (179.2 kcalmol-1) and nitrobenzene (193.4 kcalmoD1), are found in the comprehensive listing given in Reference 39. The rather high PA values for nitro compounds suggest protonation by common chemical ionization reagent systems, such as hydrogen (H3+) and methane (CH5+). [Pg.258]

Chien, C.-J M. J. Charles, K. G. Sexton, and H. E. Jeffries, Analysis of Airborne Carboxylic Acids and Phenols as Their Pentafluo-robenzyl Derivatives Gas Chromatography/Ion Trap Mass Spectrometry with a Novel Chemical Ionization Reagent, PFBOH, Environ. Sci. Technol., 32, 299-309 (1998). [Pg.640]

Dry air doped with a chemical ionization reagent (such as Cl2 for anions and acetone or NH3 for cations) sweeps the vapor through a tube containing 10 millicuries of 63Ni. Reagent gas ionized by (3-emission from 63Ni reacts with analyte to generate analyte ions. [Pg.487]

Production of Ions. Several methods are used (11 by bombardment with electrons from a heated filament (2 by application of a strong electrostatic field (field ionization, field desorption) Ot by reaction with an ionized reagent gas (chemical ionization) (4 by direct emission of ions from a solid sample that is deposited on a heated filament (surface ionization) (SI by vaporization from a crucible and subsequent electron bombardment (e.g.. Knudsen cell for high-lcmperalure sludies id solids and (6) by radio-frequency spark bomhardmenl of sample fur parts-per-biliion (ppb) elemental analysis of solids as encountered in metallurgical, semiconductor, ceramics, and geological studies. Ions also are produced by photoion izution and laser ionizalion. [Pg.971]

FIGURE 15.11 A typical hybrid Cl ionization source for the ion trap. The reagent gas is connected to the ionization chamber of the hybrid ion source. Sample molecules enter directly into the ion trap, which is separated from the ionization chamber. Chemical ionization reagent ions are pulsed into the ion trap through a lens assembly and react with sample molecules to form sample Cl ions. [Pg.451]

Chemical ionization (Q) source is very similar to the El source but the beam of electrons is used to create a plasma of ionized reagent gas (e.g., isobutane, methane, ammonia). [Pg.2776]

Tzing SH, Ghule A, Chang JY, Ling YC. Selective adduct formation by furan chemical ionization reagent in gas chromatography ion trap mass spectrometry. J Mass Spectrom. 2003 38 401-8. [Pg.116]

Another potential analytic application of gas-phase metal-ion chemistry was suggested by Preiser and coworkers but apparently as yet with no practical consequences. Pattern recognition methods were used to evaluate and demonstrate the efficacy of the rare earth metal ions Sc, Y" ", and La" " as chemical ionization reagents for molecular MS a large number of organic molecules were examined by FTICR-MS, comprising six classes alkanes, alkenes, ketones, aldehydes, ethers, and alcohols (Forbes et al., 1986a,b, 1987). [Pg.80]

In chemical ionization-mass spectrometry (CI-MS), the sample molecules are combined with a stream of ionized reagent gas that is present in great excess relative to the sample. When the sample molecules collide with the preionized reagent gas, some of the sample molecules are ionized by various mechanisms, including proton transfer, electron nansfer, and adduct formation. Almost any readily available gas or highly volatile liquid can be used as a reagent gas for CI-MS. [Pg.110]

Decomposition (fragmentation) of a proportion of the molecular ions (M +) to form fragment ions (A B+, etc.) occurs mostly in the ion source, and the assembly of ions (M +, A+, etc.) is injected into the mass analyzer. For chemical ionization (Cl), the Initial ionization step is the same as in El, but the subsequent steps are different (Figure 1.1). For Cl, the gas pressure in the ion source is typically increased to 10 mbar (and sometimes even up to atmospheric pressure) by injecting a reagent gas (R in Figure 1.1). [Pg.1]

Much of the energy deposited in a sample by a laser pulse or beam ablates as neutral material and not ions. Ordinarily, the neutral substances are simply pumped away, and the ions are analyzed by the mass spectrometer. To increase the number of ions formed, there is often a second ion source to produce ions from the neutral materials, thereby enhancing the total ion yield. This secondary or additional mode of ionization can be effected by electrons (electron ionization, El), reagent gases (chemical ionization. Cl), a plasma torch, or even a second laser pulse. The additional ionization is often organized as a pulse (electrons, reagent gas, or laser) that follows very shortly after the... [Pg.10]

As each mixture component elutes and appears in the ion source, it is normally ionized either by an electron beam (see Chapter 3, Electron Ionization ) or by a reagent gas (see Chapter I, Chemical Ionization ), and the resulting ions are analyzed by the mass spectrometer to give a mass spectmm (Figure 36.4). [Pg.255]

Because this chemical reaction occurs between the and M species, the original methane (CH4) is called a reagent gas, the CH5+ species are reagent gas ions, and the process is known as chemical ionization (Cl). [Pg.383]

Molecular ion Chemical ionization using ammonia as reagent gas establishes the molecular weights of sugar acetates. [Pg.122]

Figure 3.2 Piocesses occurring in chemical ionization mass spectrometry using methane as the reagent gas. Figure 3.2 Piocesses occurring in chemical ionization mass spectrometry using methane as the reagent gas.
Reagent gas A gas used in chemical ionization to produce species which react with molecules of the analyte of interest to produce a molecular species. [Pg.309]

The appearance and reproducibility of chemical ionization mass spectra depends on the ionizing conditions, principally the source temperature and presstire and the purity of the reagent gas. Chemical ionization mass spectra are generally not as reproducible as electron impact spectra. [Pg.482]

Representative mass spectral conditions (negative chemical ionization) ion source temperature, 150°C ionizing current, 0.20 mamp electron energy, 70 eV methane reagent gas (source pressure 0.5 to 1 torr). [Pg.55]

Resistance to physical shocks and vibration required careful attention to selection of rugged components and to securing electrical and vacuum systems, wiring, connectors, components, and boards. Chemical ionization (Cl) was used for the first time in a fieldable military detector because of the advent of rugged turbomolecular pumps capable of handling the gas load from the Cl reagent. [Pg.75]


See other pages where Chemical ionization reagent gas is mentioned: [Pg.483]    [Pg.908]    [Pg.82]    [Pg.441]    [Pg.483]    [Pg.908]    [Pg.82]    [Pg.441]    [Pg.539]    [Pg.70]    [Pg.198]    [Pg.3]    [Pg.743]    [Pg.200]    [Pg.2801]    [Pg.14]    [Pg.142]    [Pg.481]    [Pg.482]    [Pg.494]    [Pg.989]    [Pg.83]    [Pg.427]   
See also in sourсe #XX -- [ Pg.332 ]

See also in sourсe #XX -- [ Pg.1701 ]

See also in sourсe #XX -- [ Pg.352 ]




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Chemical gases

Chemical ionization

Chemical ionization mass spectrometry reagent gases

Chemical ionization other reagent gases

Chemical ionization reagent gases used

Chemical reagent gas

Ionization, chemical reagent

Ionized chemical

Ionized gases

Ionizer, gas

Reagent gas

Reagent gases, for chemical ionization

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