Mass spectrometry fragmentation patterns

Table 5. Mass spectrometry fragmentation pattern of (z>)-penicillamine...

Buhr, K., van Ruth, S., Delahunty, C. (2002) Analysis of volatile flavour compounds by proton transfer reaction-mass spectrometry fragmentation patterns and discrimination between isobaric and isomeric compounds. International Journal of Mass Spectrometry, 221,1-7. 

Mass spectral fragmentation patterns of alkyl and phenyl hydantoins have been investigated by means of labeling techniques (28—30), and similar studies have also been carried out for thiohydantoins (31,32). In all cases, breakdown of the hydantoin ring occurs by a-ftssion at C-4 with concomitant loss of carbon monoxide and an isocyanate molecule. In the case of aryl derivatives, the ease of formation of Ar—NCO is related to the electronic properties of the aryl ring substituents (33). Mass spectrometry has been used for identification of the phenylthiohydantoin derivatives formed from amino acids during peptide sequence determination by the Edman method (34). 

Mass spectrometry combines exquisite sensitivity with a precision that often depends more on the uncertainties of sampling and sample preparation than on those of the method itself. Mass spectrometry is a supreme identification and recognition method in polymer/additive analysis through highly accurate masses and fragmentation patterns quantitation is its weakness. Direct mass spectrometry of complex polymeric matrices is feasible, yet not often pursued. Solid probe ToF-MS (DI-HRMS) is a breakthrough. Where used routinely, mass spectrometrists are usually still in charge. At the same time, however, costs need to be watched. 

Mass spectrometry Characteristic mass spectral fragmentation patterns 664... 

Current detection limits are < 1 ng for full scan mass spectra and < 1 pg for multiple ion monitoring mass spectrometry. Compound identifications are based on the comparisons with authentic standards, GC retention time, literature mass spectra and the interpretation of mass spectrometric fragmentation patterns. The MS methods used for the various markers and studies are listed in Table 1. 

Both the liquid and gas products were analyzed by gas chromatography. The column for the liquid analysis was 20% Apiezon L on 60-80 mesh Chromosorb P. The column measured 1/4 inch by 7 feet. The gas analysis utilized a 1/4 inch by 10 foot column of 60-80 mesh Chromosorb 102. Temperature programming was required in both analyses. Identification of the GC peaks was based on retention time of pure compounds when these were available. In addition, two of the samples were analyzed by combined gas chromatography-mass spectrometry. By comparing the observed mass spectrometer fragmentation patterns with tabulated patterns it was possible to identify virtually every component in the product. Further details are available in the theses by Wu (23) and Early (J+). 

The mass spectral fragmentation patterns of a variety of fused and spiro thietanes and thietes were presented in CHEC(1984) and CHEC-II(1996). Only more recent data are included here. The mass spectrometry (MS) spectra of thietanes 10 and 11 show molecular ion peaks at m/z 330 and 270, respectively, corresponding to the molecular weights of thiobarbiturates used for their preparation by photolysis in acetonitrile <2003H(59)303>. The structures of different derivatives (substituted in the thietane ring by CH3, Ph, or OC2H5 groups) of 5,7,7,9-tetramethyl-l-thia-... 

Heterocyclic compounds contain hetero atoms and very often aromatic systems also. They fulfil, therefore, the conditions for the production of characteristic mass spectrometric fragmentation patterns. For this reason mass spectrometry has become especially valuable for structural investigations in this class of compounds. 

In 2012 an ESl-MS investigation of Rh-catalyzed [2 + 2 + 2] cycloaddition reaction was reported [53]. In this DFT-supported study, several key intermediates were observed and characterized by MS/MS tandem spectrometry. Although reactant and product are neutral, the charged catalyst provided a good opportunity to intercept visible intermediates. A species with m/z 974.1 was assigned based on its accurate mass and fragmentation pattern however, as is often the case with mass spectrometry-based experiments, the authors were unable to distinguish between isomeric structures (Scheme 6). 

GC-mass spectrometry (GC-MS) is most frequently and effectively used to identify the essential oil constituents by using database libraries of both retention indices and mass spectral fragmentation patterns. LC-mass spectrometry is less frequently used for the identification of the essential oil constituents due to increased experimental complexity. One of the recent technological developments is the combined use of GC-MS and FTIR spectrometries which can provide additional real time information for molecular identification without the need for macroscopic separation of mixtures [55,61-67]. 

The mass spectral fragmentations of backbone-rearranged steroids of the type (60) and the related A " -olefins are characteristic and dependent upon the configuration of the side-chain. Mass spectral fragmentation patterns are reported for a number of steroidal oximes, and for 5a-chloro-6j5-nitro-steroids, for a series of 22,26-epiminocholestane derivatives, and for 5a- and 5j5-3,6-diones. The mass spectrometry of cardenolides has been reviewed. ... 

HPLC-NMR and another hyphenated, more powerful instrument, HPLC-NMR-MS (the MS stands for mass spectrometry) are used in pharmaceutical research and development. These hyphenated techniques identify not only the structures of unknowns, but with the addition of MS, the molecular weight of unknown compounds. The HPLC-NMR-MS instrument separates the sample on the HPLC column, takes the NMR spectra as the separated components flow through the probe and then acquires the mass spectrum of each separated component to determine the molecular weight and additional structural information from the mass spectral fragmentation pattern. The MS must be placed after the NMR, since MS is a destructive technique. MS is covered in Chapters 9 and 10. 

Mass spectrometry methods have experienced a steadily increasing use in polymer analyses due to their high sensitivity (<10 mol suffice for analysis), selectivity (minor components can be analyzed within a mixture), specificity (exact mass and fragmentation patterns serve as particularly specific compositional characteristics), and speed (data acquisition possible within seconds). As mentioned, the analysis of a polymer (or any other sample) by mass spectrometry presupposes that the polymer can at least partly be converted to gas-phase ions. This chapter briefly reviews the ionization methods and instrumentation available today for the characterization of synthetic macro molecules. 

The introduction of mass spectrometry and the subsequent coupling of liquid chromatography to this very efficient system of detection has resulted in the development of many LC-MS or LC-MS/MS methods for aflatoxin analysis. Because of the advantages of specificity and selectivity, chromatographic methods coupled to mass spectrometry continue to be developed they improve detection limits and are able to identify molecules by means of mass spectral fragmentation patterns. 

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