Isotopic clusters in mass spectrometry

Gorman, M., DeMattia, D., Doonan, D., Gohlke, R.S. The calculation of relative abundance of isotope clusters in mass spectrometry. J. Chem. Educ. 47, 467 (1970)... 

Isotopic cluster In mass spectrometry, a group of peaks that differ in m/z because they incorporate different isotopes of their component elements. 

See also Biochemical Applications of Mass Spectrometry Chemical Ionization in Mass Spectrometry Cluster Ions Measured Using Mass Spectrometry Food Science, Applications of Mass Spectrometry Ion Collision, Theory Ion Molecule Reactions in Mass Spectrometry Isotope Ratio Studies Using Mass Spectrometry Isotopic Labelling in Mass Spectrometry NQR, Applications Proton Affinities Quadru-poles. Use of in Mass Spectrometry. 

Isopropyl group (Section 2 13) The group (CH3)2CH— Isotactic polymer (Section 7 15) A stereoregular polymer in which the substituent at each successive chirality center is on the same side of the zigzag carbon chain Isotopic cluster (Section 13 22) In mass spectrometry a group of peaks that differ in m/z because they incorporate differ ent isotopes of their component elements lUPAC nomenclature (Section 2 11) The most widely used method of naming organic compounds It uses a set of rules proposed and periodically revised by the International Union of Pure and Applied Chemistry... 

The mass determination of ionic species (atomic or polyatomic ions) in mass spectrometry is always a comparative measurement, which means the mass of an ionic species is determined with respect to reference masses of elements (or substances) used for mass calibration. The reference mass is thus acquired from the mass unit (m = In = 1/12) of the mass of the neutral carbon isotope (m = 1.66 X 10 kg). A mass calibration is easy to perform in solid-state mass spectrometry if the sample contains carbon (using carbon cluster ions with whole masses, as discussed above). The so-called doublet method was apphed formerly, e.g., ions and doubly charged Mg + forming a doublet at the same nominal mass number 12 were considered, where they are slightly displaced with respect to one another. The doublet method is no longer of relevance in modern inorganic mass spectrometry. Orientation in the mass spectra can be carried out via the matrix, minor and trace elements after mass calibration and by comparing the measured isotopic pattern of elements with theoretical values. 

In mass spectrometry signals are obtained for each isotope present. With the low mass resolution of quadrupole mass spectrometers ( 1 dalton), this leads to a number of isobaric interferences, which can be corrected for with appropriate software. This type of interference depends only slightly on the working conditions, which is not the case for spectral interferences resulting from doubly charged ions, background species or cluster ions. The background species at low masses [512] cause considerable spectral interferences e.g. for Si+ (with (with... 

Mass spectrometry is the only universal multielement method which allows the determination of all elements and their isotopes in both solids and liquids. Detection limits for virtually all elements are low. Mass spectrometry can be more easily applied than other spectroscopic techniques as an absolute method, because the analyte atoms produce the analytical signal themselves, and their amount is not deduced from emitted or absorbed radiation the spectra are simple compared to the line-rich spectra often found in optical emission spectrometry. The resolving power of conventional mass spectrometers is sufficient to separate all isotope signals, although expensive instruments and skill are required to eliminate interferences from molecules and polyatomic cluster ions. 

The impact of an ion beam on the electrode surface can result in the transfer of the kinetic energy of the ions to the surface atoms and their release into the vacuum as a wide range of species—atoms, molecules, ions, atomic aggregates (clusters), and molecular fragments. This is the effect of ion sputtering. The SIMS secondary ion mass spectrometry) method deals with the mass spectrometry of sputtered ions. The SIMS method has high analytical sensitivity and, in contrast to other methods of surface analysis, permits a study of isotopes. In materials science, the SIMS method is the third most often used method of surface analysis (after AES and XPS) it has so far been used only rarely in electrochemistry. 

In seeking to identify a newly prepared compound by mass spectrometry, the observation of the parent or molecular ion isotopic cluster is usually greeted with satisfaction, but observation of apparently lower or higher mje values for the parent ion causes initial confusion. However, even in a series of clotely related compounds, run in the same... 

Another approach combines the mass spectrometric derivatization approach with chemical amplification (Reiner et al., 1997, 1998). In this instrument, H02 and R02 are converted to OH through the reactions in the chemical amplifier approach discussed below, and the OH is then converted to H2S04 by reaction with S02 and measured by chemical ionization mass spectrometry using NO, (HN03) clusters as described earlier. In this case, the use of isotopically labeled S02 is not necessary, since the ambient H2S04 concentration is much smaller than that of the peroxy radicals. 

Additionally, mass spectrometry methods have been successfully applied for the identification of other Zn-containing complexes. Among them are compounds containing two Zn atoms (30-32), as well as some complexes that exist as dimers in the condensed phase according to different physical methods " (33-42). For all these compounds, isotope clusters with isotopic distributions similar to the graphical representations in Figure lb (for [Zni] ) were expected, provided that the binuclear species or dimer entities are able to survive the ionization process. 

McGibbon, G. A., Bayliss, M. A., Antler, M., Lashin, V. (2008). Automated software analysis of isotope cluster mass differences for components in LC-MS datasets. In Proceedings of the 56th ASMS Conference on Mass Spectrometry and Allied Topics, Denver, CO. 

Weidolf, L. Covey, T. R. 1992. Studies on the metabolism of omeprazole in the rat using liquid chromatography/ionspray mass spectrometry and the isotope cluster technique with [34S]omeprazole. Rapid Commun. Mass Spectrom.., 6,192-196. 

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