Charge-remote fragmentations

These two anions interconvert by the reversible pathway a, as demonstrated by the identity of the spectra of these two compounds. Other steps have been proved to be reversible by labelling experiments. Square brackets indicate ion-molecule complexes. 

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Figure 7.15. Other examples of CRF are discussed in Chapter 8. Charge remote fragmentations have been reviewed in [25,26],...

Charge-remote fragmentation is defined as a class of gas-phase decompositions that occur physically remote from the charge site [66-70]. Although the mechanism of charge-remote fragmentation is still debatable (Scheme 4) [67],... 

M. L. Gross, Charge-remote fragmentation An account of research on mechanisms and applications, Int. J. Mass Spectrom. 200 (2000), 611-624. 

C. Cheng and M. L. Gross, Applications and mechanisms of charge-remote fragmentation, Mass Spectrom. Rev. 19 (2000), 398-420. 

J. Adams and M. J. Songer, Charge-remote fragmentations for strnctnral determination of lipids, TrAC, Trends Anal. Chem. 12 (1993), 28-36. 

J. Adams, Charge-remote fragmentations analytical applications and fnndamen-tal studies. Mass Spectrom. Rev. 9 (1990), 141-186. 

An important issue in fatty acid analysis is the stractural characterization, especially in terms of positions of double-bond, hydroxy, and other groups. Although results with low-energy negative-ion ESI-MS-MS was described [13], the MS-MS analysis of lithiated lithium salts [M-H+2Li] is the method of choice. Determination of the double-bond position relies on charge-remote fragmentation [2, 14]. 

Deterding, L. J. and Gross, M. L. Tandem mass spectrometry for identifying fatty acid derivatives that undergo charge-remote fragmentations. Org. Mass Spectrom. 23 169-177, 1988. 

Figure 12 The mass spectrum of the fatty acid methyl ester (FAME) of linolenic acid (C18 2A9-12) contains no readily discernable structural information beyond the molecular ion (a). However, the dimethyloxazoline (DMOX) derivative, in which the charge is retained by the heterocyclic ring, can undergo charge remote fragmentation yielding a mass spectrum from which the location of the double bonds, but not their geometry (c/ s versus trans), can be readily determined (b). The latter stereochemistry can usually be distinguished by the GC retention time on an appropriate column.

Hsu F.F., Turk J., Studies on sulfatides by quadrupole ion-trap mass spectrometry with electrospray ionization structural characterization and the fragmentation processes that include an unusual internal galactose residue loss and the classical charge-remote fragmentation, Journal of the American Society for Mass Spectrometry 15 (2004) 536-546. 

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