Collisional-induced decomposition

Metastable ions yield valuable information on fragmentation in mass spectrometry, providing insight into molecular structure. In electron ionization, metastable ions appear naturally along with the much more abundant normal ions. Abundances of metastable ions can be enhanced by collisionally induced decomposition. 

Measurements are performed with a conventional geometry instrument and the reactions occurred in the first FFR (unimolecular or collisional-induced decompositions). The value of the transitions is determined by measuring the E/Eq ratio, which yields nii/mi (m and m2 unknown) each term can be determined as soon as the ion beam which emerges from (— E) leaves the magnetic field at the value m2/mi. Thus, Wj and m2 can be calculated. 

These examples of this methodology show the usefulness of MS/MS, especially in the case of mixtures isomeric linkages can be identified peptide sequences (during either spontaneous or collisional-induced decompositions) can be determined. 

In addition to distinguishing the disaccharide linkage bond in various stereomeric species, measurements of collisional-induced decompositions (as MIKE/CAD spectra) also enable one to differentiate the diastereomeric disaccharides themselves, providing that protonated molecular ions are not used [236]. 

In the case of mixtures, molecular ions appear as a function of temperature, which does not simplify their detection. Nevertheless, the presence of doubly (or triply) charged molecular ions (as [M-l-2Na] ) enables the determination of the molecular species (cationized or protonated). In this case, even when the compounds are of high molecular weight, such as Mani-Me-Mang-OCH3 ([M -l-Na] ion, m/z 1801.8), it is possible to study collisional-induced decompositions in B/E linked scan. The limitations of this method are related above all to the loss of sensitivity, due to the necessity of using an... 

It is possible to show that the relative quantities of derivatives of deoxyguanosine, deoxyadenosine and deoxycytidine are present at 92, 7 and 1 %. Collisional-induced decompositions of each of these peaks (B/F/CAD) are required, since spontaneous decompositions are relatively few. 

Hie arrangement of the QQQs along the same axis can lead to same noise in the MS/MS spectra. In fact, by considering the collisionally induced decomposition... 

Positive ion fast atom bombardment (FAB) mass spectra were obtained with the JEOL HXllO/HXllO tandem double-focusing mass spectrometer with JEOL gun and collisionally induced decomposition (CID) MS/MS. The JEOL instrument was operated at +10 kV with -20 kV postacceleration at the detector. The xenon neutral beam had 6 kV acceleration from the JEOL gun. CID MS/MS was performed with 1 1000 resolution in both MS-1 and MS-2. Helium was used as the collision gas at a pressure sufficient to reduce precursor ion abundance by 75%. Samples were dissolved in methanol-glycerol (1 1, v/v) for all FABMS analyses. 

CID = Collisionally induced decomposition PB = Particle beam GC = Gas chromatography LC = Liquid chromatography SFC = Supercritical fluid chromatography... 

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