Enhanced Induced Fragmentation

Collision of an ion with an inert gas molecule leads to some deflection in the ion trajectory. After several collisions, the ion could have been deflected so much that it no longer reaches the detector. This effect attenuates the ion beam as it passes through the gas cell, leading to loss of instrumental sensitivity. An attenuation of 50 to 70% is acceptable and is not unusual in practice. 

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. 

Linked Scanning and Metastable Ions in Quadrupole Mass Spectrometry 

The steps (reactions) by which normal ions fragment are important pieces of information that are lacking in a normal mass spectrum. These fragmentation reactions can be deduced by observations on metastable ions to obtain important data on molecular structure, the complexities of mixtures, and the presence of trace impurities. 

1 momentum by acceleration through a (small) electric potential 

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The helium gas in the trap not only helps in trapping the ions but also cools them (i.e., the kinetic energy of a trapped ion is dissipated through repeated collisions with the He gas), thus forcing the ions to the center of the trap where the quadrupole field is best defined. Both sensitivity and mass resolution are significantly enhanced by the presence of the He gas. Moreover, the same He can also be used to induce fragmentation when working in the MS" mode (see below). 

Traditional sample preparation conditions to form SDS-protein complexes prior to electrophoretic analysis included heat treatment at elevated temperatures (e.g., In the case of non-reduced rMAbs, this could lead to sample preparation artifacts in the form of thermally induced fragmentation attributed to disulfide reduction and exchange reactions. Moreover, it was reported that high pH (>9.0) also enhanced the... 

Paul, G., Winnik, W., Hughes, N., Schweingruber, H., Heller, R., and Schoen, A. (2003). Accurate mass measurement at enhanced mass-resolution on a triple quadrupole mass-spectrometer for the identification of a reaction impurity and colfisionally-induced fragment ions of cabergoline. Rapid Commun. Mass Spectrom. 17 561-568. 

The three major approaches of ELISA, LC-FLD, LC-MS are likely to continue to be applied to the currently increasing demand for information on occurrence. ELISA techniques are limited in the information provided and as they give variable between-run results, they are therefore best used as semiquantitative tools. Only LC-FLD and LC-MS/MS enable the identification and quantification of the major ergot alkaloids and their epimers. Mass spectrometry is required. LC-MS and LC-MS/MS methods provide unequivocal identification of the alkaloids, and the ability to obtain structural information through collision-induced fragmentation greatly enhances its usefulness for confirmation and elucidation of structure confirmation. LC-MS/MS methods therefore could be preferred to LC-FLD however, the capital costs of equipment are higher. 

To enhance the overlap of the IR beam with the trapped ion cloud, the copper excite-electrodes of the ICR cell are polished and serve as a multipass reflection cell for the laser beam the curvature of the electrodes naturally refocuses the beam (in one direction only) on each pass. The off-axis geometry of the PEL beam has the additional advantage that a second laser beam can access the imi cloud on-axis. A C02-laser can, for instance, be used in addition to the PEL to induce dissociation, so that product ions can be mass-isolated and spectroscopically investigated. Moreover, a C02-laser can be employed to enhance the fragmentation yield. 

A powerful tool to enhance the analytical potential of combined chromatography-MS especially in LC-MS, is tandem MS (MS/MS). MS/MS was first introduced as a way to induce fragmentation of ions generated in the ion source, e.g. by soft ionization methods, and after their mass selection. In such an experiment, the first mass spectrometer selects a particular precursor ion, which is (collisionally) dissociated, and the product ions are analysed with the second mass spectrometer. This is the product-ion scan mode which is primarily used to elucidate the structures of ions. 

The minimal in-source CID inherent in the ion source of ESI not only dramatically enhances the ionization sensitivity of ESI/MS, but also makes ESI/MS a powerful tool for quantitative applications since colUsion-induced fragmentation is a process that depends on the molecular structure of the analytes. Accordingly, ESI has currently become the method... 

Positive ion FAB mass spectra obtained with a double focusing mass spectrometer produced abundant molecular ions ([M] +) of carotenes and xanthophyUs with minimal fragmentation and no detectable thermal decomposition. Fragmentation of the precursor ion was enhanced by collision-induced dissociation (CID) using helium gas. ... 

Enhanced molecular ion implies reduced matrix interference. An SMB-El mass spectrum usually provides information comparable to field ionisation, but fragmentation can be promoted through increase of the electron energy. For many compounds the sensitivity of HSI can be up to 100 times that of El. Aromatics are ionised with a much greater efficiency than saturated compounds. Supersonic molecular beams are used in mass spectrometry in conjunction with GC-MS [44], LC-MS [45] and laser-induced multiphoton ionisation followed by time-of-flight analysis [46]. 

Vascular Effects of Complement Activation. During complement activation a number of complement fragments (anaphylatoxins), which are polypeptides with inflammatory properties, are released. The anaphylatoxins C3a and C5a induce smooth muscle contraction and enhance vascular permeability (H31). The most pronounced activation of complement with the formation of anaphylatoxins and terminal C5-9 complexes has been observed in septic shock (B29, B30, P2). Studies indicate that there is a relation between high concentrations of anaphylatoxins and C5-9 complexes and the development of ARDS or MODS in patients with sepsis (H10). 

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