Negative ion FAB mass spectrum

Negative ions FAB mass spectrum of poly(butadiene) ozonolysis products. (Reprinted with permission from Ref. 76, Copyright 1999, American Chemical Society.)... 

Figure 12.3 Negative-ion FAB mass spectrum of a branched-chain sodium alkylbenzene suiphonate in a glycerol matrix.

Fig. 5. Negative ion FAB mass spectrum (a) of d(G-A-A-G-A-T-C-T-T-C) and the corresponding shorthand structure (b) with those bonds marked which on breakage give rise to...

The partial positive ion FAB mass spectrum (obtained by Xe bombardment) is shown in Fig. 2 and incorporates an abundant protonated molecular ion at m/z 1040. Three clearly defined series of diagnostic fragment ions, corresponding to the general structures (1) (N-terminal), (2) (N-terminal) and (3) (C-terminal) identify the sequence as PhCO-Ala-Phe-Val-Ile-Asp-Asp-Glu-Gln (or /.yo-Gln). The negative ion FAB spectrum showed an abundant [M —H] ion at m/z 1038 and the series of ions corresponding to structure (4) was able to confirm the sequence of the six C-terminal amino acids. 

Fig. 9.5. Negative-ion FAB spectrum of solid Csl. The monoisotopic [(Csl)nl] cluster ion series (cf. expanded view of m/z 2205.4) is well suited for calibrating a wide mass range.

Figure 9.18 Mass spectrometry of glycerides, phospholipids and fatty adds, (a) origin of main fragmentation ions as illustrated (b) (c) Example of negative ion FAB MS/MS CID mass spectrum of indicated fatty acid. The main fragment ions visible are homologation fragment anions. Mass differences between consecutive fragment anions define fatty acid CH2-length (

Fig. 7. B/E constant linked scan spectra of [M-H] ions at m/z 1002 and 974 in negative ion mode FAB mass spectrum of fraction II.

FAB matrix spectra are generally characterized by a series of matrix (Ma) cluster ions accompanied by some more abundant fragment ions in the lower m/z range. In positive-ion FAB, [Ma +H]" cluster ions predominate, while [Ma -H]" cluster ions are preferably formed in negative-ion FAB (Fig. 10.7). The principal ion series may be accompanied by [Ma H-alkali] ions and some fragments of minor intensity, e.g., [Ma H-H-H20]. The fragment ions detected below the [Ma-nH] ion, which normally also gives rise to the base peak, are almost the same as observed in the positive-ion Cl mass spectrum of the respective matrix conpound [43]. 

Figure 2. Negative FAB mass spectra of maitotoxin. The numbers denote the mass number at the centroid of each peak. A A survey scan at a low resolution (R=300). B. Resolution enhanced spectrum (R=3000) for ion clusters at around m/z 3300. C. Resolution enhanced spectrum (R=3000) for ion clusters at around miz 3400.

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