Mass electron-impact ionization

It is well known that the electron-impact ionization mass spectrum contains both the parent and fragment ions. The observed fragmentation pattern can be usefiil in identifying the parent molecule. This ion fragmentation also occurs with mass spectrometric detection of reaction products and can cause problems with identification of the products. This problem can be exacerbated in the mass spectrometric detection of reaction products because diese internally excited molecules can have very different fragmentation patterns than themial molecules. The parent molecules associated with the various fragment ions can usually be sorted out by comparison of the angular distributions of the detected ions [8]. 

Mass Spectra. Obtained by Gillis et al (Ref 104). Field ionization and electron impact ionization mass spectra are given by Brunee et al (Ref 54) Mechanical Properties < Sound Velocity. Hoge (Ref 77) obtained the following ultimate stress as a function of strain rate for machined discs (1.77g/cc) of PETN (all failures were brittle fractures)... 

J.J. Jimenez, J.L. Bernal, S. Aumente, M.J. delNozal, M.T. Martin, J. Bernal, Quality assurance of commercial beeswax I. Gas chromatography electron impact ionization mass spectrometry of hydrocarbons and monoesters, Journal of Chromatography A, 1024, 147 154 (2004). 

Application of electron impact ionization mass spectrometry (EI-MS) techniques for the analysis of 1,2-thiazines has waned since the publication of CHEC-II(1996). In one recent example of this technique, bicycle 44 was ionized at 70 eV and 180°C to afford radical cation 53, 54 via loss of CO2, and W-sulfinyl compound 55 and 1,3-cyclohexa-diene radical cation 56 via a retro-[44-2] reaction in the gas phase (Scheme 5) <2002TA2407>. 

The electron impact ionization mass spectrum of cortisone acetate was obtained using solid probe introduction, using a Shimadzu QP-Class-5000 gas chromatography mass spectrometer system. The most prominent ions observed, and their relative intensities, are shown in Table 6. 

Field desorption and electron impact ionization mass spectra were taken by using a Matsuda type double focussing spectrometer... 

GC-EI-MS gas chromatography coupled with electron impact ionization mass spectrometry... 

C,HJ (Benzene) sf6- >0 Unspecified Photoionization -mass spectrometry Single-source electron-impact ionization-mass spectrometry CeH (QHj —)C,2H SF6 (XFVSFJXFj- X-Se.Te,U SF6-(TeF6 SF6,F)TeF5- The ion SF - produced by thermal electron capture of SF in a vibrational degree of excitation equal to electron affinity of the neutral 116a... 

Gas phase molecular aggregates that contain acid molecules have been produced with free jet expansion techniques and detected by using electron impact ionization mass spectrometry. The clusters of aqueous nitric acid paralleled many properties of the condensed phase. Multiple nitric acid molecules were found in the clusters that were sufficiently dilute. The acid molecule was absent in the ionized clusters involving HC1 and only water was evident. Experiments also demonstrated the reactivity of ammonia with aqueous nitric acid and sulfur dioxide clusters and of sulfur trioxide with water clusters. The natural occurrence of acid cluster negative ions offers a means to probe the gas phase acid loading of the atmosphere through laboratory and field studies of the ion chemistry. 

In thermal ionization mass spectrometry (TI-MS), solid, inorganic compounds may be volatilized from a heated surface. TI-MS is the most precise method for the measurement of isotopic ratios of minerals and has been used to analyze 58pe in fecal samples collected from a human study (H). The major drawbacks of this technique are the costly instrument and the slow sample through-put. Conventional mass spectrometry produces ions by electron bombardment of the vapor of volatile compoimds. This is called electron-impact ionization mass spectrometry (EI-MS). Analysis of iron by EI-MS requires derivitization to volatile forms before introduction into the mass spectrometer. A method has been developed for the synthesis of volatile iron-acetylacetone chelates from iron in blood serxm (1 ). A tetraphenylporphyrin chelate has also been synthesized and used in an absorption study in which 54pe and 57pe were given orally (16). 

Amelung, W., and Brodowski, S. (2002). In vitro quantification of hydrolysis-induced racemization of amino acid enantiomers in environmental samples using deuterium labeling and electron-impact ionization mass spectrometry. Anal. Client. 74, 3239-3246. 

FIGURE 12.4 Electron impact ionization mass spectra of water (A) and acetaminophen (B). The intensities of the fragment ions are normalized against those of the predominant ion (base peak), which, in the case of water, is also the molecular ion with mass/charge ratio im/z) = 18. 

Two compartment Knudsen cells were used by Gesenhues and Wendt [456] as well as Schafer and Florke [457] to study the vapor over AlCl3(s). The electron impact ionization mass spectra of AlCl3(g) and (AlCl3)2(g) as well as the trimerization enthalpy of AlCl3(g) resulted. 

Nieto R, Calder AG, Anderson SE, et al. 1996. Method for the determination of 15NH3 enrichment in biological samples by gas chromatography electron impact ionization mass spectrometry. J Mass Spectrom 31(3) 289-294. 

Figure 9.2 Electron impact ionization mass spectra of JP-10 in argon as a function of flow-tube temperature.

HR-EI-MS = High Resolution-Electron Impact Ionization-Mass Spectrometry. 

Maki, E. Pihlaja. M. Kleinpeter, E. Hartmann. J. Schroth, W. Electron impact ionization mass spectra of some 4,9-dihetero-(X,X)-cyclodeca-1,6-dienes Mono- and di-benzo analogs. Acta Chem. Scand. 1994. 48. 319- 323. 

Ion attachment mass spectrometry (lAMS) has proven to be a rMque method that complements electron-impact ionization mass spectrometry for the determination of components in chemical processes and environments, such as microwave discharge plasma. The identification of intermediate free radicals and other species in chemical reactions is particularly challenging. One of the greatest advantages of lAMS is that it can be used to directly analyze gaseous compounds. The features that allow this system to detect the intermediate free radicals (refer to Sect. 5.2.4) and novel molecular species produced in various plasmas have been extensively explored (Sect. 5.2.7), and lAMS techniques can be used to identify and quantify compounds and mixtures under plasma and pyrolysis (Sect. 6.4) conditions. To extend the ion attachment technique to ion trap mass spectrometry (Sect. 6.5) or time-of-flight mass spectrometry (Sect. 6.6) has been realized. 

Our "work-horse method of identifying the reaction products is electron impact ionization mass spectrometry. We feel that this method is one of the most generally universal for all chemical species and sufficiently adaptable for fast measurements to be the central focus in the instrument design. It is now a well developed technique developed by chemical kineticists during the... 

Retinol and retinyl esters tend to dehydrate under the conditions of electron-impact ionization mass spectroscopy, so that the most prominent ion is that of anhydroretmol (m/z 268) instead of retinol (m/z 286), with small but detectable amounts of the parent ion (20). Methyl retinoate and the trimethylsilyl derivative of retinol usually give prominent molecular ions by electron-impact ionization. Chemical ionization usually gives an identifiable adduct to the molecular ion, thus providing useful information on molecular weight. 

Electron Impact Ionization Mass Spectra of Common Solvents... 

Soltmann B, Sweeley C C, Holland J F 1977 Electron impact ionization mass spectrometry using field desorption activated emitters as solid sample probes. Anal Chem 49 1164-1166... 

Figure 4 Typical instrumental configurations for pyrolysis electron-impact ionization mass spectrometry direct insertion probe pyrolysis mode (upper) and Curie-point pyrolysis mode (lower). Reproduced by permission of Elsevier Science from Meuzelaar HLC, Windig W, Huff SM and Richards JM (1986). Analytica Chimica Acta 190 119-132.

Fig. 4.3. Application of chemical-ionization and electron-impact ionization mass spectrometry to the identification of the 12-lipoxygenase product, 12-ketoeicosatetraenoic acid. Neural tissue from the marine mollusk, Aplysia californica, was incubated for 30 minutes in the presence of exogenous arachidonate (50 jjM). The incubates were extracted with organic solvent, and fractionated by HPLC. HPLC fractions containing 12-ketoeicosatetraenoic acid were brought to dryness, subjected to appropriate derivatization reactions, and analyzed by GC/MS using either negative-ion chemical ionization (top) or electron-impact ionization (bottom). The relatively simple spectrum obtained by chemical ionization provides information on the molecular mass of the compound. The electron-impact spectrum supports this information (a molecular ion of m/z 332 is visible) and provides additional elements for the unambiguous identification of the analyte. (Reproduced with permission from Piomelli Detal.J Biol Chem 1988 263 16591-16596.)...

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