Collision-induced dissociation , type

Tandem quadrupole and magnetic-sector mass spectrometers as well as FT-ICR and ion trap instruments have been employed in MS/MS experiments involving precursor/product/neutral relationships. Fragmentation can be the result of a metastable decomposition or collision-induced dissociation (CID). The purpose of this type of instrumentation is to identify, qualitatively or quantitatively, specific compounds contained in complex mixtures. This method provides high sensitivity and high specificity. The instrumentation commonly applied in GC/MS is discussed under the MS/MS Instrumentation heading, which appears earlier in this chapter. 

Apparatus, developed in this laboratory for two types of thermochemical measurements—(a) gas-phase ion molecule equilibria and (b) collision-induced dissociation (CID) threshold measurements—will be described. For both purposes, a triple quadrupole mass spectrometer is used. It is only the front end modifications that provide the conditions for (a) or (b). 

There are multiple ways of detecting metastable and collision-induced dissociations with magnetic sector instruments. [82] In fact, the phenomenon was discovered with this particular type of mass analyzer (Chap. 2.7.1). [83,84]... 

Figure 13 Peptide Fragmentation Results in the Ions Shown. Collision-Induced Dissociation Spectra Often Result in the Dominant Fragmentation at the Amide Bonds in the Polyamide Backbone, Producing Ions of the Type b or y...

The reactions of Mg+ with cyanoacetylene are remarkable in that while Mg is unreactive towards HCN, multiple ligation occurs for cyanoacetylene . Furthermore, there is evidence from collision induced dissociation (CID) studies that ligand-ligand interactions occur. In fact, the Mg(NC3H)4+ is especially stable, being resistant to CID. DFT calculations suggest that the semibulvalene-type structure, 4, is around 12 kcalmoU more... 

The effects of electronically excited reactant ions (AB+) on collision-induced dissociations have been studied in a number of systems, including those for which AB+ =0, N, N0+,C0+, and for which the neutral target is either a rare-gas atom or another neutral molecule. Various reactions of this type that have been investigated are included in Table I. 

Other means of manipulating ions trapped in the FTMS cell include photodissociation (70-74), surface induced dissociation (75) and electron impact excitation ("EIEIO")(76) reactions. These processes can also be used to obtain structural information, such as isomeric differentiation. In some cases, the information obtained from these processes gives insight into structure beyond that obtained from collision induced dissociation reactions (74). These and other processes can be used in conjunction with FTMS to study gas phase properties of ions, such as gas phase acidities and basicities, electron affinities, bond energies, reactivities, and spectroscopic parameters. Recent reviews (4, 77) have covered many examples of the application of FTMS and ICR, in general, to these types of processes. These processes can also be used to obtain structural information, such as isomeric differentiation. 

Triple quadrupole mass spectrometry can provide rapid screening of complex mixtures for specific compounds and can be used to analyze for compounds that cannot routinely be analyzed by GC/MS. In addition, structural information can be obtained for certain types of compounds since in collision-induced dissociations the fragments are likely to show the structual differences of the parent compounds. Complex mixtures have been analyzed by this technique by introducing the sample directly into the heated sample port of the instrument with little or no sample pretreatment. Triple quadrupole mass spectrometry promises to be a useful, cost-effective, and practical advanced technique for environmental analysis, particularly when applied to hazardous waste problems. 

A special type of mass spectrometric system is an MS/MS (e.g. [45]). In an MS/MS system the ions are generated by any of the available procedures (common El or Cl ionizations are used). The process continues with the ion separation using one of the systems previously described. A particular ion A (named parent ion) is then selected and further dissociated by collision with the molecules of a gas N (collision induced dissociation-CID or collision activated dissociation-CAD) in a reaction zone of the MS/MS system. The common reaction taking place in the CID zone can be described as follows ... 

There are three main types of mass analyzers in ESTMS-MS instruments triple quadrupole, ion traps, and quadrupole-time-of-flight (Q-TOF). There are several differences between the mass analyzers in MALDI-TOF and in ESI-MS-MS. Unlike in MALDI-TOF-MS, in ESTMS-MS two mass analyzers are used in tandem to increase the sensitivity of the technique. The peptide ions produced by the ESI sources are carried to the first mass analyzer and only peptides of a set miz ratio are selected. The selected ions are then carried to a collision cell where they are subjected to additional fragmentation to produce smaller amino acid ions using a process called as collision induced dissociation (CID). The CID process employs inert gases such as argon for the dissociation of peptides. These smaller amino acid ions are then resolved in the second mass analyzer before sending to the detector. This process essentially enables highly sensitive detection of actual amino acid sequence of the peptides based on the mIz ratios of individual amino acids. 

In this case both chemical reaction (3 a) and collision-induced dissociation (3 b), denoted CID, can occur. During the course of this work we developed a theoretical method for distinguishing the two (nearly) degenerate electronic product states produced in CID [12, 13]. This type of analysis gives considerable insight into the dissociation process. The extensive literature on H + He collisions is reviewed in Refs. 11-13. Finally, we have studied charge-transfer in the symmetric system [14]... 

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