High-resolution electron impact mass spectrometry

HREI-MS high-resolution electron-impact mass spectrometry... 

Demethylsonodione (7), a p-quinonoid aporphine, was obtained as greenish prisms. Its molecular formula was determined as C19H17O5N by high-resolution electron impact mass spectrometry (HREIMS) at m/z 339.1098 [M]+ [24]. The UV spectrum with maxima at 219, 283, 336, and 642 nm was typical of a p-quinonoid aporphine skeleton [53]. In its IR spectrum, absorption bands at 3440 cm 1 (phenolic hydroxyl) and 1635 cm 1 (carbonyl) were apparent. The H-NMR spectrum indicated signals... 

Various mass spectral techniques have been used in characterizing various metal-containing macromolecules. The focus will be on two techniques. The first one is the most commonly employed mass spectrophotometer setup, called high-resolution electron impact mass spectrometry (HREl-MS). The second system is the matrix-assisted laser desorption ionization (MALDl) system. Illustrative examples of these two procedures are given for the products of Group IVB metallocene dichlorides and the antibacterial drug norfloxacin, scheme 8. 

Azonazine is an unusual hexaqrdic dipeptide that includes a diketopiperazine moiety that was isolated from the Hawaiian marine sediment-derived fungus Aspergillus insulicola The absolute configuration was established by extensive nuclear magnetic resonance (NMR), high-resolution electron impact mass spectrometry (HREIMS) and circular dichroism (CD) analysis. 

High resolution electron impact mass spectral analyses were carried out at the Midwest Center for Mass Spectrometry, University of Nebraska, Lincoln, Nebraska. The samples were rapidly heated to about 450 C. 

Diphenylthiirene 1-oxide and several thiirene 1,1-dioxides show very weak molecular ions by electron impact mass spectrometry, but the molecular ions are much more abundant in chemical ionization mass spectrometry (75JHC21). The major fragmentation pathway is loss of sulfur monoxide or sulfur dioxide to give the alkynic ion. High resolution mass measurements identified minor fragment ions from 2,3-diphenylthiirene 1-oxide at mje 105 and 121 as PhCO" and PhCS, which are probably derived via rearrangement of the thiirene sulfoxide to monothiobenzil (Scheme 2). 

Abbreviations m/z is the mass-to-charge ratio, M is the molecular weight of the molecule itself, M+ is the molecular ion, HRMS is high-resolution mass spectrometry, FAB is fast atom bombardment, and EIMS is electron-impact mass spectrometry. 

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

Figure 5. Electron impact mass spectrum of tetraethyleneglycol-di(2-ethylhex-anoate), compound 82. The elemental compositions of m/e 127 and 171 were established by high resolution mass spectrometry the A values indicate the error (in millimass units) between measured and calculated exact masses.

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