Isotopic clusters in mass

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. 

Elements with distinctive isotope ratios (Cl, Br, and transition metals, for example) will provide a distinctive isotopic cluster in the mass spectrum of a compound. This can be used to identify the presence of elements within unknown compounds. 

Figure 17 Nanospray tandem mass spectrum, obtained with CAD in Q1 of a qQq FTMS, for a hybrid glycan from Xenopus PO, after release by PNGase F and permethylation (45). Inset shows expansion of isotopic cluster in the molecular ion region of the precursor, [M+2Na] miz 1206.586. Reproduced with permission from (45).

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. 

Knowing what to look for with respect to isotopic clusters can aid in interpreting mass spectra How many peaks would you expect to see for the molecular ion in each of the following compounds At what m/z values would these peaks appear (Disregard the small peaks due to and )... 

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... 

Not only the molecular ion peak but all the peaks in the mass spectrum of benzene are accompanied by a smaller peak one mass unit higher. Indeed, because all organic compounds contain car bon and most contain hydrogen, similar isotopic clusters will appear in the mass spectra of all organic compounds. 

Establishing the elemental composition based on the isotopic peaks may be problematic if, for example, the sample contains impurities with the masses in the region of the molecular ion cluster. In the El mass spectra of amines, alcohols, acids, and some other classes of organic compounds there is often a peak of [M + H]+ ion. It distorts the isotopic picture. It is worth mentioning as well that in real experimental conditions the peak intensity may vary slightly in each... 

The relevance of oxygen and sulfur isotopic patterns is nicely demonstrated by the cluster ion series in fast atom bombardment (FAB) spectra of concentrated sulfuric acid, where the comparatively large number of sulfur and oxygen atoms gives rise to distinct isotopic patterns in the mass spectrum (Chap. 9). 

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... 

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. 

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