Mass spectrometry aromatic compounds

This system was studied by Schwartz. Toluene at 10 ppm, nitric oxide at 1 ppm, and nitrogen dioxide at 1.2 ppm were irradiated with ultraviolet lamps in a 17-m batch reactor for 270 min. Collected aerosols were successively extracted with methylene chloride and then methanol. The methylene chloride extract was fractionated into water-soluble and water-insoluble material, and the latter fraction was further divided into acidic, neutral, and basic fractions. The acidic and neutral fractions were analyzed by gas chromatography and chemical-ionization mass spectrometry the compounds identified are shown in Figure 3-7. The two analyzed fractions represented only about 5.5% of the total aerosol mass. It is noteworthy that classical nitration of an aromatic ring appears to... 

Inks and prints are analysed in order to ensure safety. This includes testing for harmful substances with potential to migrate into food. Environmental pressure may result in a demand for testing, for example, vegetable oils versus petroleum distillates. There might also be a need to determine the content of aromatic compounds in the ink in order to avoid odour and taint problems. For chemical analysis of prints and determination of ink components a number of methods are available, such as pyrolysis, infra-red spectrometry, gas chromatography and mass spectrometry. Volatile compounds are usually analysed by a headspace technique. The progress in chemical analysis is so rapid that any method may be considered obsolete after a limited number of... 

Process solvents SRC s, and liquefaction products also were examined by column chromatography (11). The sample was dissolved in chloroform or THF, pre-adsorbed on neutral alumina (12), and eluted from neutral alumina to give saturates, aromatics, and three polar fractions. The saturate fraction was analyzed quantitatively by mass spectrometry, and compound identification in distillates and solvents was confirmed by combined GC-MS or high-resolution MS analysis of column chromatography fractions. 

This test method does not cover the determination of the percentage mass of aromatic compounds in oils since NMR signals from both saturated hydrocarbons and aliphatic substituents on aromatic ring compounds appear in the same chemical shift region. For the determination of mass or volume percent aromatics in hydrocarbon oils, chromatographic, or mass spectrometry methods can be used. 

The stability of isothiazole derives from the fact that it has an aromatic delocalized ir-electron system. The NMR chemical shifts, which depend, inter alia, on ring currents, and the high stability of the molecular ions in mass spectrometry, are typical of aromatic compounds, and X-ray measurements confirm the partial double bond character of all the bonds of the ring. 

To identify the volatile components, gas chromatography-mass spectrometry (GC-MS) is still the method of choice. A comparison of the GC fingerprints of B. carter a and B. serrata reveals the different composition of the volatile fractions (Figure 16.1). Common monoterpenes, aliphatic, and aromatic compounds of olibanum are, e g., pinene, limonene, 1,8-cineole, bomyl acetate, and methyleugenol (Figure 16.2). 

Enhanced molecular ion implies reduced matrix interference. An SMB-El mass spectrum usually provides information comparable to field ionisation, but fragmentation can be promoted through increase of the electron energy. For many compounds the sensitivity of HSI can be up to 100 times that of El. Aromatics are ionised with a much greater efficiency than saturated compounds. Supersonic molecular beams are used in mass spectrometry in conjunction with GC-MS [44], LC-MS [45] and laser-induced multiphoton ionisation followed by time-of-flight analysis [46]. 

In an acetone extract from a neoprene/SBR hose compound, Lattimer et al. [92] distinguished dioctylph-thalate (m/z 390), di(r-octyl)diphenylamine (m/z 393), 1,3,5-tris(3,5-di-f-butyl-4-hydroxybenzyl)-isocyanurate m/z 783), hydrocarbon oil and a paraffin wax (numerous molecular ions in the m/z range of 200-500) by means of FD-MS. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out (Chapter 2). The method of Dinsmore and Smith [257], or a modification thereof, is normally used. Mass spectrometry (and other analytical techniques) is then used to characterise the various rubber fractions. The mass-spectral identification of numerous antioxidants (hindered phenols and aromatic amines, e.g. phenyl-/ -naphthyl-amine, 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinoline, butylated bisphenol-A, HPPD, poly-TMDQ, di-(t-octyl)diphenylamine) in rubber extracts by means of direct probe EI-MS with programmed heating, has been reported [252]. The main problem reported consisted of the numerous ions arising from hydrocarbon oil in the recipe. In older work, mass spectrometry has been used to qualitatively identify volatile AOs in sheet samples of SBR and rubber-type vulcanisates after extraction of the polymer with acetone [51,246]. 

Organic compounds polycyclic aromatic hydrocarbons, in particular phenan-threne (C14H10), pyrene (Ci6Hjo) and chrysene (CisH ), which were detected using high resolution mass spectrometry. 

The chromatograms of the liquid phase show the presence of smaller and larger hydrocarbons than the parent one. Nevertheless, the main products are n-alkanes and 1-alkenes with a carbon number between 3 to 9 and an equimolar distribution is obtained. The product distribution can be explained by the F-S-S mechanism. Between the peaks of these hydrocarbons, it is possible to observe numerous smaller peaks. They have been identified by mass spectrometry as X-alkenes, dienes and also cyclic compounds (saturated, partially saturated and aromatic). These secondary products start to appear at 400 °C. Of course, their quantities increase at 425 °C. As these hydrocarbons are not seen for the lower temperature, it is possible to imagine that they are secondary reaction products. The analysis of the gaseous phase shows the presence of hydrogen, light alkanes and 1-alkenes. 

Recent studies, including the use of Microtox and ToxAlert test kits [55,56], were carried out for the determination of the toxicity of some non-ionic surfactants and other compounds (aromatic hydrocarbons, endocrine disruptors) before implementation on raw and treated wastewater, followed by the identification and quantification of polar organic cytotoxic substances for samples with more than 20% inhibition. Furthermore, the study of their contribution to the total toxicity was obtained using sequential solid-phase extraction (SSPE) before liquid chromatography-mass spectrometry (LC-MS) detection. This combined procedure allows one to focus only on samples containing toxic substances. 

Ortho-Effect. The ortho-effect is one of the most widely known structural phenomena in organic chemistry. It is widely used in organic chemistry for synthetic purposes. The mass spectra of the majority of ort/jo-substituted aromatic compounds possess significant differences in comparison with the spectra of their meta- and para-isomers. A classic example of the ortho-effect in mass spectrometry involves fragmentation of alkylsalicylates. The intense peaks of [M - ROH]+ ions dominate in the El spectra of these compounds. These peaks are absent in the spectra of their meta- and para-isomers. The reaction leading to these ions may be represented by Scheme 5.12. 

For more volatile compounds in soils, such as aromatic hydrocarbons, alcohols, aldehydes, ketones, chloroaliphatic hydrocarbons, haloaromatic hydrocarbons, acetonitrile, acrylonitrile and mixtures of organic compounds a combination of gas chromatography with purge and trap analysis is extremely useful. Pyrolysis gas chromatography has also found several applications, heteroaromatic hydrocarbons, polyaromatic hydrocarbons, polymers and haloaromatic compounds and this technique has been coupled with mass spectrometry, (aliphatic and aromatic hydrocarbons and mixtures of organic compounds). 

Bay, Massachusetts. Gas liquid chromatography was used to detect hydrocarbons present at different depths in the sediment, while low resolution mass spectrometry was employed to measure concentrations of paraffins, cycloparaffins, aromatics and polynuclear aromatics. Their data show that the concentrations of total and saturated hydrocarbons decreased with increased depth, and it was noted that identification and quantification of hydrocarbons in oil-contaminated sediments is required if the fate of these compounds in dredge spills is to be determined. 

The sites of protonation of aromatic compounds, including the possible three mono fluoronitrobenzenes, have been studied by neutralization-reionization mass spectrometry (NRMS)22. The NRMS experiments on the MD+ species generated by D2 chemical ionization clearly indicated that the D+ attachment takes place to the nitro group rather than to the aromatic ring, as evidenced by the abundant losses of OD and DNO2 (NO + OD )22. 

The spectroscopic properties of meso-ionic compounds have been discussed in detail elsewhere and the reviewers do not feel that it would be useful to include a comprehensive account here. Ultraviolet, infrared, and nuclear magnetic resonance spectra of meso-ionic heterocycles provide general support for the conjugative interaction that would be expected for aromatic heterocycles, " but detailed interpretation of their spectra is not justifiable. Mass spectrometry has been shown to be particularly useful for distinguishing between pairs of meso-ionic isomers... 

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