Ion cyclotron resonance ICR spectrometer

Operation of the ion cyclotron resonance (ICR) spectrometer under equilibrium conditions allows the determination of K2 for the equilibrium in... 

The two-photon photochemistry of C6H5Br has been studied in an ion cyclotron resonance (ICR) spectrometer. A pump-and-probe technique... 

Gaseous NH4 ions were generated in a Fourier transform ion cyclotron resonance (ICR) spectrometer by the reaction of formaldehyde with NH2 [5] via the steps... 

An ion cyclotron resonance (ICR) spectrometer creates a pulse of ions in a magnetic field. These are brought into resonance by scanning the applied radiofrequency. From the cyclotron resonance frequency and the magnetic field strength the mlz ratio can be calculated. The use of a fast Fourier transform (FT-ICR) refines the method. 

The most widely used type of trap for the study of ion-molecule reactivity is the ion-cyclotron-resonance (ICR) [99] mass spectrometer and its successor, the Fourier-transfomi mass spectrometer (FTMS) [100, 101]. Figure A3.5.8 shows the cubic trapping cell used in many FTMS instmments [101]. Ions are created in or injected into a cubic cell in a vacuum of 10 Pa or lower. A magnetic field, B, confines the motion in the x-y... 

Other types of mass spectrometer can use point, array, or both types of ion detection. Ion trap mass spectrometers can detect ions sequentially or simultaneously and in some cases, as with ion cyclotron resonance (ICR), may not use a formal electron multiplier type of ion collector at all the ions can be detected by their different electric field frequencies in flight. 

In obtaining experimental information about the isomeric forms of ions, a variety of techniques have been used. These include ion cyclotron resonance (ICR),31 flow tube techniques, notably the selected ion flow tube (SIFT),32 and the selected ion flow drift tube (SIFDT)32 (and its simpler variant33), collision induced dissociation (CID),10,11 and the decomposition of metastable ions in mass spectrometers.13 All of these techniques are mentioned in the text of Section in whore they have provided data relevant to the present review. 

Usually, concentration is measured as a pressure and may differ widely according to the type of mass spectrometer used. The triple quadrupole mass spectrometer may operate with pressures up to 1 x 10 1 Pa in the reaction region. At the other extreme, ion cyclotron resonance mass spectrometers operate poorly at pressures >1 X 10 4 Pa. A pressure of 1 x 10 4 Pa may be regarded as fairly high pressure for FT-ICR measurements. Converting the pressure into a more normal value of concentration means that reactions are carried out at concentrations < 10 9M (often several orders of magnitude < 10 0 M). 

Figure 16.8—Ion cyclotron resonance (ICR) mass spectrometer. Ion trajectories in the ICR cell are shown. Plates 5 and 6 are used for excitation, plates 3 and 4 are used to trap ions and plates 1 and l are used as the detection system. Ions can be formed inside or outside the ICR cell. Exampleofthe tg resouion a can be obtained with this type of spectrometer (R = 3 x I06), cf. 16.8.3.

Thus the interpretation of ESI-MS spectra of POPAM dendrimers recorded on an FT-ICR (Fourier-Transform Ion Cyclotron Resonance) mass spectrometer leads to drastic overestimation of defects in the sample molecules (Fig. 7.4). The... 

Concerning the first field of application, the kinetics and equilibrium constants for several halide transfer reactions (equation 1) were measured in a pulsed electron high pressure mass spectrometer (HPMS)4 or in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR)5. From measurements of equilibrium constants performed at different temperatures, experimental values were obtained for the thermochemical quantities AG°, AH° and AS° for the reaction of equation 1. The heat of formation (AH°) of any carbocation of interest, R+, was then calculated from the AH0 of reaction and the AH° values of the other species (RC1, R Cl and R +) involved. 

The lifetimes of ions studied by ion cyclotron resonance (ICR) are commonly of the order of milliseconds [254], In terms of eqn. (9), the limits tx and t2 of the observation window are zero and of the order of milliseconds, respectively. Reactive ions of longer lifetimes are not distinguished from those with the more usually encountered lifetimes (< /is). Using ICR, it has been found that decomposition of the molecular ion of 1, 5-hexadiyne (c.f. Sect. 5.7) to lose H occurs predominantly at times greater than microseconds [344], An ICR mass spectrometer constituting the second half of a tandem mass spectrometer has been used to study decomposition of propane ions up to times of milliseconds [775], The observation window in this case extended from tx — /is to... 

Some mass spectrometers combine several types of analysers. The most common ones include two or more of the following analysers electromagnetic with configurations EB or BE, quadrupoles (Q), ion traps (ITs) with Paul ion traps or linear ion traps (LITs), time-of-flight (TOF), ion cyclotron resonance (ICR) or orbitrap (OT). These are named hybrid instruments. The aim of a hybrid instrument is to combine the strengths of each analyser while avoiding the combination of their weaknesses. Thus, better performances are obtained with a hybrid instrument than with isolated analysers. Hybrids are symbolized by combinations of the abbreviations indicated in the order that the ions travel through the analysers. 

The laboratory study of IS ion chemistry has its origins in measurements of bimolecular ion/molecule reaction kinetics. Experimental conditions that are found in most of the mass spectrometers employed in the measurement of bimolecular ion/molecule reactions are far from those found in the cold low-pressure environments of space. Nevertheless, because of the pressure independence of bimolecular reactions and the absence of significant activation energies in most bimolecular ion/molecule reactions, MS measurements performed here on earth do have relevance for the chemistry in space. The substantial database available in the early 1990s on the kinetics of bimolecular ion/molecule reactions important in IS chemistry [8-10] was obtained almost entirely using ion cyclotron resonance (ICR) and flow-tube (FT) mass spectrometry techniques. Both techniques are well established and continue to be used extensively for ion/ molecule reaction measurements generally. 

Although FAB has been used in polymer analysis, problems with fragmentation and the relatively low mass limit has made this less popular as new techniques have emerged. Plasma desorption has been used successfully but this too has waned in popularity with commercial spectrometers not really readily available. To a large extent polymer mass spectrometry equates to MALDI time-of-flight and the remainder of this article will bear this in mind. However, the use of electrospray ionisation (ESI) will be considered in conjunction with either quadrupole detectors or ion cyclotron resonance (ICR) N. B. ICR detectors can also be used with MALDI, as this is important and probably not as widely used as it could be. 

Closely related to the omegatron mass spectrometer is the ion cyclotron resonance (ICR) mass spectrometer. Sommer and Thomas devised the ICR mass spectrometer by combining the techniques of nuclear magnetic resonance absorption and the basic omegatron. Wobschall, Graham and Malone and Henis have described the ICR spectrometer in detail and indicated its applications to the study of ion-molecule reactions and of negative ions. Baldeschwieler and Woodgate have reviewed ICR spectroscopy and included discussions of the... 

Next to CE, on-line coupling of capillary lEF and MS is attractive. For protein characterizatiorr, CIEF-MS on a Fourier-transform ion-cyclotron resonance mass spectrometer (FT-ICR-MS) irrstrament was pioneered by the group of Smith [99-100]. They demonstrated the high-resolution analysis of E. coli proteins, reveahng >400 proteins (2-100 kDa) from an injection of only 300 ng. 

Given the complexity of the oligonucleotide MS and MS-MS spectra, the application of high-resolntion instmments like Fonrier-transform ion-cyclotron resonance mass spectrometers (FT-ICR-MS) is beneficial. While some initial results were reported in the mid-1990s, e.g., [37-38], the fieqnent ntilization of FT-ICR-MS in oligonucleotide characterization is more recent (Ch. 22.3.3). 

Traditionally, ion traps have been divided into three classes QIT, which rely on RF fields to provide ion trapping a linear ion trap, which is closely related to the QIT in its operating principles and ion cyclotron resonance (ICR) mass spectrometers, which rely on a combination of magnetic fields and electrostatic fields for trapping. 

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