Electron ionization-Mass spectrometry EI-MS

Since dithio- and selenocarbamates and their derivatives are used so widely in the deposition of thin films and nanoparticles that a mechanistic study of their decomposition behavior was carried out by O Brien et al. [ 107]. Wold et al. [78] studied the decomposition products of Zn(S2CNEt2)2 using gas-chromatography mass spectrometry (GC-MS) and their reported deposition path shows clean ehmination of ZnS from the precursor (Eqs. 1 and 2 below). However, the proposed decomposition route is somewhat different to the step-by-step fragmentation observed in the electron-ionization mass spectrometry (EI-MS) of the compoimd, (Eq. 3). This difference can be attributed to inherent differences between the two techniques. 

The technique we have described is called electron ionization mass spectrometry (EI-MS). This technique was the first one developed and for a time was the one most widely used. It is limited, however, to relatively low-molecular-weight compounds that are vaporized easily in the evacuated ionization chamber. 

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>. 

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). 

Structural information about toxaphene components can be obtained by gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS), positive ion chemical ionization mass spectrometry (GC/PICI-MS) or negative ion chemical ionization MS(GC/NICI-MS). Mass separation is performed by low resolution quadrupole or high resolution magnetic field instruments, by ion trap systems (GC/IT-MS), or by tandem mass spectrometry (MS/MS) offering a broad spectrum of possibihties. 

Derivatization for Gas Chromatography-Electron Ionization Mass Spectrometry (GC-EI-MS)... 

Methods other than electron bombardment (EI-MS) can be used to obtain mass spectral data. In chemical ionization-mass spectrometry (CI-MS), the sample is sprayed with a pre-ionized gas such as methane or ammonia that causes the sample to ionize by electron transfer or proton transfer from the gas to the sample. Because the molecular ions produced by this technique are less apt to undergo fragmentation, the ability to obtain the molecular mass (and therefore the molecular formula) of the sample is enhanced. 

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

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

Nonylphenol polyethoxylates and their degradation products have been detected in river water and sewage effluent by GC-ion trap (tandem) MS with electron impact (El) and chemical ionization, which was followed by direct GC-MS analysis in EI-MS, chemical ionization mass spectrometry (CIMS), or CIMS—MS modes. 

Analysis of pesticides (eight in total, namely, molinate, propanil, fenitrothion, malathion, bentazone, cypermetrine, maloxon, and fenitrothion oxon) in biota was accomplished with a method based on pressurized liquid extraction (ASE), followed by SPE clean-up, and analysis by gas chromatography-mass spectrometry with electron impact ionization (GC/MS-EI). 

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