Analysis, mass-spectral

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. 

Everninornicin D is the principal component from cultures of M.icromonospora carbonacae (10). Its stmcture (5) was elucidated using extensive chemical degradation coupled with spectroscopic analysis and it was the first reported instance of a natural product containing a tertiary nitrosugar. X-ray analyses of both the olgose residue (9) and the nitrosugar (16) have been reported as has a complete mass spectral analysis of everninornicin D (8). 

In Surface Analysis by Laser Ionization (SALI), a probe beam such as an ion beam, electron beam, or laser is directed onto a surfiice to remove a sample of material. An untuned, high-intensity laser beam passes parallel and close to but above the sur-fiice. The laser has sufficient intensity to induce a high degree of nonresonant, and hence nonselective, photoionization of the vaporized sample of material within the laser beam. The nonselectively ionized sample is then subjected to mass spectral analysis to determine the nature of the unknown species. SALI spectra accurately reflect the surface composition, and the use of time-of-flight mass spectrometers provides fast, efficient and extremely sensitive analysis. 

The red fox (Vulpes vulpes) uses a chemical communication system based on scent marks in urine. Recent work has shown one component of fox urine to be a sulfide. Mass spectral analysis of the pure scent-mark component shows M+ = 116. IR spectroscopy shows an intense band at 890 cm-1, and H NMR spectroscopy reveals the following peaks ... 

Solvolyses of these cyclic vinyl triflates at 100 in 50% aqueous ethanol, buffered with triethylamine, lead exclusively to the corresponding cyclo-alkanones. Treatment of 176 with buffered CH3COOD gave a mixture of cyclohexanone (85%) and 1-cyclohexenyl acetate (15%). Mass spectral analysis of this cyclohexanone product showed that the amount of deuterium incorporation was identical to that amount observed when cyclohexanone was treated with CH3COOD under the same conditions. This result rules out an addition-elimination mechanism, at least in the case of 174, and since concerted elimination is highly unlikely in small ring systems, it suggests a unimolecular ionization and formation of a vinyl cation intermediate in the solvolysis of cyclic triflates (170). The observed solvent m values, 174 m =. 64 175 m =. 66 and 16 m =. 16, are in accord with a unimolecular solvolysis. 

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

Tetrachlorodiben2o- >-dioxin. Purified 2,4,5-trichlorophenol (50 grams, 0.26 mole) was converted to its potassium salt and dissolved in 100 ml of bEEE. After addition of the copper catalyst and ethylene diacetate, the mixture was transferred to the bottom of a 300-ml sub-limer with chloroform. Sublimation (200°C/2 mm) yielded 14 grams (39% yield) of 2,3,7,8-tetrachlorodibenzo-p-dioxin. Mass spectral analysis revealed trace quantities of pentachlorodibenzo-p-dioxin, tetrachloro-dibenzofuran, and several unidentified substances of similar molecular weight. The combined impurity peaks were estimated to be <1% of the total integrated GLC area. The product was further purified by recrystallizations from o-dichlorobenzene and anisole. The final product had an estimated 260 ppm of trichlorodibenzo-p-dioxin as the only detected impurity. 

The mass spectral analysis of an iron sample gives the following data. 

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. 

A great deal of interest has been shown in the mass spectral analysis of natural products. In most cases it is desirable to develop techniques incorporating g.l.c. to enable the separation of the components obtained in extracts from natural products. The volatility required for g.l.c. is... 

Molecular weight determination by mass spectral analysis... 

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... 

There are two basic approaches to direct mass-spectral analysis of volatile additives, namely constant-temperature heating and temperature-programmed heating (sometimes called thermolysis-mass spectrometry,... 

An effective means to facilitate the mass-spectral analysis of rubber acetone extracts is to use desorp-tion/ionisation techniques, such as FD [92,113] and FAB [92]. FAB mass spectra for rubber extracts are generally more complex (due to fragment ions) than FD spectra of the same materials. Nevertheless, the FAB spectra are often complementary to FD, since ... 

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... 

The minor alkaloid gelsedine, originally isolated from G. sempervirens in 1953 (3), has also been found in G. elegans (19). The structure of gelsedine (6) has been determined by means of H-NMR and mass spectral analysis (4,9)... 

An interesting variation on the whole-cell MALDI approach was recently reported in a study aimed more at FTMS than TOF MS, but the results are nevertheless interesting and important to users of both methods for analysis of bacteria 40. Wilkins s group showed both MALDI-TOF and MALDI-FTMS spectra of whole bacteria grown on isotopic media depleted in C13 and N14. Because most bacterial identification protocols involve a culture step prior to analysis, it is possible to manipulate the sample based on control of the growth media. For mass spectral analysis manipulation of the isotope profile... 

J. Uy, M. Tanaka, T. Kishimoto, Y. Mass spectral analysis of complex lipids desorbed directly from lyophilized membranes and cells. Biochem. Biophys. Res. Comm. 1987,142,194-199. 

The results for bacterial whole-cell analysis described here establish the utility of MALDI-FTMS for mass spectral analysis of whole-cell bacteria and (potentially) more complex single-celled organisms. The use of MALDI-measured accurate mass values combined with mass defect plots is rapid, accurate, and simpler in sample preparation then conventional liquid chromatographic methods for bacterial lipid analysis. Intact cell MALDI-FTMS bacterial lipid characterization complements the use of proteomics profiling by mass spectrometry because it relies on accurate mass measurements of chemical species that are not subject to posttranslational modification or proteolytic degradation. 

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