Spectral analysis Compounds”

Mass spectral analysis of quaternary ammonium compounds can be achieved by fast-atom bombardment (fab) ms (189,190). This technique rehes on bombarding a solution of the molecule, usually in glycerol [56-81-5] or y -nitroben2yl alcohol [619-25-0], with argon and detecting the parent cation plus a proton (MH ). A more recent technique has been reported (191), in which information on the stmcture of the quaternary compounds is obtained indirectly through cluster-ion formation detected via Hquid secondary ion mass spectrometry (Isims) experiments. 

The procedure we have described retains the generality of normal mass spectral analysis. It is particularly suited, however, to compounds... 

C03-0089. Combustion analysis of 0.60 g of an unknown organic compound that contained only C, H, and O gave 1.466 g of carbon dioxide and 0.60 g of water in a combustion analysis. Mass spectral analysis showed that the compound had a molar mass around 220 g/mol. Determine the empirical formula and molecular formula. 

The H-NMR spectra of compound 71a in DMSO-de showed the presence of a signal at 12.5 ppm corresponding to the exchangeable NH proton, the ethylenic proton as a singlet at S 5.6 ppm, and the aromatic protons appear between 7.27 and 7.80 ppm. The elemental and spectral analysis was in agreement with the structures of these compounds. 

Day-to-day variations in flow rate, check valve efficiency, or mixing solenoid performance (in binary, ternary, or quaternary pumping systems) can also contribute to retenbon shifts. Therefore, compound identification should be performed only by spiking with a known standard or by direct identification with, for example, mass spectral analysis. 

Principles and Characteristics Mass-spectral analysis methods may be either indirect or direct. Indirect mass-spectral analysis usually requires some pretreatment (normally extraction and separation) of the material, to separate the organic additives from the polymers and inorganic fillers. The mass spectrometer is then used as a detector. Direct mass-spectrometric methods have to compete with separation techniques such as GC, LC and SFC that are more commonly used for quantitative analysis of polymer additives. The principal advantage of direct mass-spectrometric examination of compounded polymers (or their extracts) is speed of analysis. However, quite often more information can be... 

Thermolysis-mass spectrometry is ideal for examining the amount of residual monomer and processing solvents present in polymers. In thermolysis, the polymer is heated from room temperature to 200-300 °C, and is then often held isothermally in order to drive off volatile components. Low-temperature pyrolysis (350-400 °C) of PP compounds in direct mass-spectral analysis has shown volatiles from PP at every carbon number to masses well above 1000 Da [37]. 

Relatively few descriptions of direct mass spectral analysis of plastics compounds have appeared in the literature [22,37,63,240,243], Additives in PP were thermally desorbed into a heated reservoir inlet for 80 eV EI-MS analysis [240], Analysis of additives in PP compounds via direct thermal desorption ammonia CI-MS has been described [269] and direct mass spectrometric oligomer analysis has been reported [21],... 

In chromatography-FTIR applications, in most instances, IR spectroscopy alone cannot provide unequivocal mixture-component identification. For this reason, chromatography-FTIR results are often combined with retention indices or mass-spectral analysis to improve structure assignments. In GC-FTIR instrumentation the capillary column terminates directly at the light-pipe entrance, and the flow is returned to the GC oven to allow in-line detection by FID or MS. Recently, a multihyphenated system consisting of a GC, combined with a cryostatic interfaced FT1R spectrometer and FID detector, and a mass spectrometer, has been described [197]. Obviously, GC-FTIR-MS is a versatile complex mixture analysis technique that can provide unequivocal and unambiguous compound identification [198,199]. Actually, on-line GC-IR, with... 

C-N.m.r. data for only a limited number of model compounds of this nature are currently available (see later). The 13C-n.m.r. data for the a-D-Man — Ser linkages, given in Tables IV and V, have already been discussed. Their application to 13C-spectral analysis has been shown in Figs. 1 and 4, and in the discussion of the glycoprotein glucoamylase. They allowed specific, resonance assignments to be made for the respective spectra. 

Barbier et al. (2004) investigated the effects of a highly selective and novel non-imidazole H3 receptor antagonist, 1, l-[4-(3-piperidin-l-yl-propoxy)-benzyl]-piperidine (JNJ-5207852), on sleep and wakefulness in mice and rats. Systemic injections of JNJ-5207852 (1-10 mg/kg, s.c.) increased the time spent in wakefulness with a concomitant decrease in NREM and REM sleep in both mice and rats. The overall increase in wakefulness was due to an increase in the number of wakefulness bouts. Spectral analysis of the EEG also revealed a reduction in total delta power following systemic injections of this compound (Barbier et ah, 2004). 

One of the major problems has been to determine the site of attachment of the PAH to the base. Some information may be obtained directly from the nmr spectra eliminating certain points of attachment. As mentioned above, if the C-8 proton of guanine or adenine can be identified, then this cannot be the point of attachment of the carcinogen. Estimation of the pKa s of the adducts either by titration (108) or partition (110) has, however, provided additional valuable information. Mass spectral fragmentation patterns can be of help in determining the site of substitution as well as in determining which bases are involved in binding (108.111-113). Substantial advances have been made in recent years on the mass spectral analysis of involatile compounds and derivatization is not always essential (114-118). X-ray analysis of DNA adducts has, to date, only been applied to model systems (119-121). 

JOC3570). Diazotization of l-methylimidazole-5-carbohydrazide (103) followed by treatment with r-butanol gave the carbamate (104), which was dissolved in cold tetrafluoroboric acid when evolution of gas had ceased, the solution was treated with sodium nitrite and irradiated. However, unlike the 4-aminoimidazoles (Section III,A,2), this reaction produced none of the desired 5-fluoro-l-methylimidazole (105) (Scheme 10). Although 5-amino-1-methylimidazole (96 R = Me, R2 = H) was almost certainly formed, ultraviolet spectral analysis showed only traces of a diazo-nium chromophore after addition of nitrite, indicating compound (96 R1 = Me, R2 = H) to be extremely unstable under the acidic reaction conditions (78JOC3570). 

This layer is then analysed directly by internal reflectance infra-red spectroscopy. Since there is no handling of the sample, contamination is reduced to a minimum. However, only infra-red spectral analysis is possible with this system since the material absorbed on the germanium prism is always a mixture of compounds, and since the spectrophotometer used for the production of the spectra is not a high-precision unit, the information coming from this technique is limited. While identification of specific compounds is not usually possible, changes in spectra, which can be related to the time of day, season, or to singular events, can be observed. 

In order to characterise the components further, mass spectral analysis was carried out. When head space volatiles from undigested cow slurry were analysed on a non-polar column the results (Figure 5) demonstrated the presence of several sulphur containing compounds—methanethiol, carbon disulphide, dimethyl sulphide, 2-propanethiol,... 

The similar fractions were combined and further chromatographed on small columns when necessary. The relevant fractions were further separated and cleaned by preparative TLC. Compounds 1,2,3, 4,5,6 were isolated. They were identified on the basis of H NMR, NMR, IR and Mass spectral analysis. 

---