Elemental Composition Report

Measured Mass Formula Calculated Mass Error Unsaturation 

The peak at m/z 158 fails no test for a molecular ion. If this is indeed the molecular ion, there are several possible elemental compositions to be considered (we neglect atoms other than C, H, N, and O). 

With regard to the fragment peaks, the M - 28 peak at m/z 130 is most indicative of the expulsion of ethylene but may also be formed by the loss of a molecule of carbon monoxide. The remaining fragment ions are equally ambiguous, but the high-resolution data in Table 3.3 clarify every question and transform this into a relatively simple problem. 

The empirical formula of the compound is C8H14O3 with two rings or double bonds. The M - C2H4 ion (m/z 130) along with the M - OC2H5, ion (m/z 113) is characteristic of an ethyl ester function. This is corroborated by the ion at m/z 88 (C4H8O2), which corresponds to the McLafferty rearrangement product. 

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Constant volume heat capacities for Hquid organic compounds were estimated with a four parameter fit (219). A 1.3% average absolute error for 31 selected species was reported. A group contribution method for heat capacities of pure soHds andHquids based on elemental composition has also been provided (159). 

Elemental analysis was performed on various coals, pitches, and blends. Table 7 reports the elemental composition of products from WVGS 13407. Compared to the raw coal, the NMP-soluble extract (EXT) contams essentially the same amount of carbon, though there is slightly more hydrogen as mdicated by a... 

A slightly different use of accurate mass measurement in drug metabolism studies has been reported [31]. In this investigation, the accurate masses of the ions derived from Glyburide (Figure 5.48) and some of its metabolites were used to calculate the difference in mass, and thus the elemental composition, between certain of the ions observed in the spectra of the various compounds. 

In the data above, the first line provides the chemical name, a comment, the elemental composition, the phase, and the temperature range over which the data are reported. In lines 2 through 4, the high-temperature coefficients ah..., a7 are presented first followed by the low temperature coefficients. For more information, refer to Kee et al. (Kee, R. J., Rupley, F. M and Miller, J. A., The Chemkin Thermodynamic Database, Sandia Report, SAND87-8215B, reprinted March 1991). 

A number of investigators have reported proximate analyses and elemental composition of textile mill dusts and trash. Only two of these involve studies of dusts collected with an elutri-ator sampler (20,31). Samples from both of these studies were collected in a model card room at North Carolina State University (42). In one of these, glass fiber filters were used and the dusts were analyzed for average ash contents (see Table IV). The total ash content was about 20%. The average ash content of area samples also collected on glass filters was found to be slightly lower. 

Aluminophosphate-Based Molecular Sieves In 1982 a major discovery of a new class of aluminophosphate molecular sieves was reported by Wilson et al. [26]. By 1986 some 13 elements were reported to be incorporated into the aluminophosphate frameworks Li, Be, B, Mg, Si, Ti, Mn, Fe, Co, Zn, Ga, Ge and As [27]. These new generations of molecular sieve materials, designated AlP04-based molecular sieves, comprise more than 24 structures and 200 compositions. 

PLS (partial least squares) multiple regression technique is used to estimate contributions of various polluting sources in ambient aerosol composition. The characteristics and performance of the PLS method are compared to those of chemical mass balance regression model (CMB) and target transformation factor analysis model (TTFA). Results on the Quail Roost Data, a synthetic data set generated as a basis to compare various receptor models, is reported. PLS proves to be especially useful when the elemental compositions of both the polluting sources and the aerosol samples are measured with noise and there is a high correlation in both blocks. 

All the coalified wood samples examined in this report were of lignite rank, as determined by their elemental compositions (Table 1). The one sample from the Moscow Basin was not analyzed for its elemental composition but was collected from a well-known Carboniferous lignite deposit. Figure 1 shows the solid-state 13c NMR data for some of the samples. Though the spectra show a large, broad... 

The use of a monoalkyltrichlorosilane in the Wurtz-type polymerization is reported to yield (RSi) referred to as polyalkylsilyne [Bianconi et al., 1989]. The elemental composition and NMR spectra of the polymer suggest a three-dimensional crosslinked structure. 

Certain software algorithms such as the one mentioned previously uses the high-quality exact mass data from the high-resolution TOF systems to report calculated elemental compositions within the results browser. Good scientific practice mandates the use of an internal reference or lock mass to obtain valid exact mass measurements (sub-5-ppm). Exact mass measurement gives greater confidence in the confirmation of expected metabolites and allows the prediction of the elemental composition of unknowns. The Q-TOF mass spectrometer can be set up to automatically acquire exact mass LC-MS and exact mass MS-MS data to within the recommended mass accuracy guidelines of 5 ppm. 

The ultimate analysis (elemental composition) of petroleum is not reported to the same extent as it is for coal (Speight, 1994). Nevertheless, there are ASTM procedures (ASTM, 1995) for the ultimate analysis of petroleum and petroleum products but many such methods may have been designed for other materials. 

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