Elemental composition determination

A compound with the elemental composition determined by mass spectrometry, was... 

The C NMR spectrum of the metabolite shows 16 signals instead of 8 as expected from the elemental composition determined by high-resolution mass spectrometry. Moreover, aromaticity of the 2,6-xylenol is obviously lost after metabolism because two ketonic carbonyl carbon atoms (5c = 203.1 and 214.4) and four instead of twelve carbon signals are observed in the shift range of trigonal carbon nuclei (5c = 133.1, 135.4, 135.6 and 139.4) in the C NMR spectra. To conclude, metabolism involves oxidation of the benzenoid ring. 

Library identification of nontargeted nonpolar molecules Elemental composition determination Structural analysis of high-mass molecules... 

As shown in Fig. 4.8, the mass difference between the two metabolites is 36.4 mDa and a mass spectrometer with a resolving power of at least 9500 (M/AM = 344/ 0.0364 = 9450) is required to separate between these two metabolites. MS/MS fragmentation combined with accurate mass measurement is the preferred method for structural elucidation of metabolites, especially when it can help to correlate the elemental composition determined in the MS mode. In the example shown in Fig. 4.8, exact mass measurements of the precursor ions are used as lock mass to measure the exact mass of each fragment ion. Exact mass measurements of the fragment ion at m/z 226 help to narrow down the sites of modifications and allows one to distinguish between rabeprazole-sulphide and rabeprazole-aldehyde. 

These isotopes are responsible for the peaks in the mass spectrum appearing as isotopic clusters that are characteristic of the elemental composition. They provide important analytical data. Indeed, even without exact mass measurement, the possibilities for elemental composition determination can often be restricted by using isotopic abundance data. For example, the fragments CioH2o and C x 11 i 2O2, both with a nominal mass of 140 u, produce peaks at mass 141 with 11 and 8.8 %, respectively, of the abundance at mass 140 u. This is the result of a different statistical probability of having 13C isotopes. These two elemental compositions can thus be distinguished in a mass analysis. 

May BCR (1975) An ultimate cascade impactor for aerosol assessment. J Aerosol Sci 6 1-7 Nieuwenhuijsena MJ, Gomez-Perales JE, Colvile RN (2007) Levels of particulate air pollution, its elemental composition, determinants and health effects in metro systems. Atmos Environ 41 7995-8006... 

Irrespective of the plasma parameters, the elemental composition, determined by XPS, is rather constant around 60 at% carbon and 40 at% fluorine (Table 2). The shapes of different components in the high resolution spectrum of the CF4 plasma-treated surfaces are associated with the signatures of C-H, C-C bonds (1, 285 eV), CHF-CH2 (2, 287.1 eV), CF (3, 289.1 eV), CF2 (4, 291.2 eV), CF3 (5, 293.0 eV) whose proportions depend on treatment duration (Fig. 6). After 1 min treatment, the major components correspond to CH2 in a position of fluorinated carbon, CF. At 3 min duration, CF proportion increases and CF2 and CF3 bands appear, with CF2 as a major component. For 15 min duration, the surface is rich in CF and... 

Elemental composition Determination of substructures Screening for unknowns ... 

Fortunately, some of the weaknesses may be overridden by using better hardware. Thus, higher mass resolution helps in molecular formula determination (Sections 8.7 and 8.8). Additional spectroscopic analyses (e.g. AAS, AES) provide additional information for element composition determination if available, e.g. the empirical formula (cf. Definition 1.25). Under such circumstances the molecular formula determination is unambiguous in many cases. 

M. Rojas-Cherto, P. Kasper, E. Willighagen, R. Vreeken, T. Hankemeier, and T. Reijmers. Elemental composition determination based on MS". Bioinformatics, 27(17) 2376-2383, 2011. 

The uniform deposit feature of the MOUDl cascade impactor was designed to facilitate the elemental composition determination of the deposits by X-ray fluorescence analysis (Dzubay and Rickel, 1978). The uniform deposit is achieved by using multiple nozzles at each stage and rotating the impaction plate beneath the nozzles (Marple et al., 1981). By placing the nozzles at specific distances from the centre of rotation, a uniform deposit is obtained upon the rotating impaction plate. 

L D., et at. "Characterization of Document Paper Using Elemental Compositions Determined by Inductively Coupled Plasma Mass Spectrometry." Journal of Analytical Atomic Spectroscopy 75 (2000), 813-819. Reproduced by permission of The Royal Society of Chemistry. 

Erve JCL, Gu M, Wang Y, De Maio W, Talaat RE (2009) Spectral accuracy of molecular ions in an Itq/orbitrap mass spectrometer and implications for elemental composition determination. J Am Soc Mass Spectrom 20(ll) 2058-2069. doi 10.1016/j.jasms.2009.07.014 European Commission (2002) Commission Decision 2002/657/EC implementing Council Directive 96/23/EC concerning performance of analytical methods and the interpretation of results. Off J Eur Commim L221/8... 

The instrument manufacturers often imply that accurate mass measurements (and therefore elemental composition determinations) are a single measurement solution to many structural problems. This is an oversimplification. A recent report, stemming from a metabolomics application, presents data that highly accurate mass measurements, even at sub-1 ppm accuracy, are insufficient to identify metabolites.Isotopic abundance pattern analysis is a necessary additional constraint to eliminate false elemental composition candidates. 

Figure 1 presents the survey spectrum of an original powder sample. The spectram demonstrates photoelectron C Is and O Is peaks and related to them C KW and O KW Auger peaks. No either peak has been found. Elemental composition determined by XPS using atomic sensitivity factors (ASF) is close to It should be noted... 

Structure (the indene nucleus) was suggested based on its elemental composition determined as QHg. In contrast, the dissociation pathway to the fragment ion at m/z 70 was suggested to include the formation of a 1-methyl-azetidine residue and the loss of C13H9O2 (-215 Da, route... 

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