Ion cyclotron resonance instrument

Commercial mass analyzers are based almost entirely on quadrupoles, magnetic sectors (with or without an added electric sector for high-resolution work), and time-of-flight (TOE) configurations or a combination of these. There are also ion traps and ion cyclotron resonance instruments. These are discussed as single use and combined (hybrid) use. 

An added consideration is that the TOF instruments are easily and quickly calibrated. As the mass range increases again (m/z 5,000-50,000), magnetic-sector instruments (with added electric sector) and ion cyclotron resonance instruments are very effective, but their prices tend to match the increases in resolving powers. At the top end of these ranges, masses of several million have been analyzed by using Fourier-transform ion cyclotron resonance (FTICR) instruments, but such measurements tend to be isolated rather than targets that can be achieved in everyday use. 

A simple mass spectrometer of low resolution (many quadrupoles, magnetic sectors, time-of-flight) cannot easily be used for accurate mass measurement and, usually, a double-focusing magnetic/electric-sector or Fourier-transform ion cyclotron resonance instrument is needed. 

There are two kinds of Type (2) ion trap mass spectrometers the quadrupole ion trap and the ion cyclotron resonance instruments. 

Ion conducting glasses, 12 585-586 Ion-cut process, 14 448-449 Ion cyclotron (ICR) analyzers, 15 663-664 Ion cyclotron resonance instrument, 15 664 Ion-dipole interactions, 14 411-418 Ion doping, in photocatalysis, 19 94-95 Ion doses, measuring, 14 444—445 Ion engines, cesium application, 5 705 Ion exchange, 14 380-426... 

Fig. 1.29 Diagram of an ion cyclotron resonance instrument. The magnetic field is oriented along the z-axis and ions ( ) are trapped according the same axis. Due to the cyclotronic motion the ions rotate around the z-axis in the x-y plane.

Milgram, K. E. Abatement of spectral interferences in elemental mass spectrometry design and construction of inductively coupled plasma ion sources for Fourier Transform ion cyclotron resonance instrumentation, Ph. D. Thesis, University of Florida, 1997, Diss. Abstr. Int., B 1998, 59(2), 639. 

Various forms of tandem mass spectroscopy (MS/MS) have also been used in the analysis of biomolecules. Such instruments consist of an ionisation source (ESI or MALDI or other) attached to a first mass analyser followed by a gas-phase collision cell. This collison cell further fragments the selected ions and feeds these ions to a second mass detector. The final mass spectrum represents a ladder of fragment ions. In the case of peptides the collision cell usually cleaves the peptides at the amide bond. The ladder of resulting peptides reveals the sequence directly [496]. Thus, tandem MS instruments, such as the triple quadrupole and ion-trap instruments have been routinely applied in LC-MS/MS or ESI-MS/MS for peptide sequencing and protein identification via database searching. New configurations, which have been moving into this area include the hybrid Q-TOF [498], the MALDI-TOF-TOF [499] and the Fourier transform ion cyclotron resonance instruments [500]. 

A mass analyzer separates and mass-analyzes the ionic species. Magnetic and/or electric fields are used in mass analyzers to control the motion of ions. A magnetic sector, quadrupole, time-of-fiight, quadrupole ion trap, quadrupole linear ion trap, orbitrap, and Fourier transform ion cyclotron resonance instrument are the most common forms of mass analyzers currently in use (discussed in Chapter 3). 

Quadrupole-Fourier Transform Ion Cyclotron Resonance Instrument... 

Multidimensional mass spectrometry (MS) involves the use of two or more mass analysis procedures one after the other in order to facilitate the selective fragmentation of specific ions in a complex mixture. Many different types and configurations of instruments can be used, some of which separate the consecutive mass analysis events spatially, while others carry out two or more analyses in the same compartment but separate them temporally. Tandem mass spectrometry (MS/MS or MS ) often involves two physically distinct mass analyzers separated by a collision cell to induce the fragmentation of precursor (primary or parent) ions. Higher-order analysis (MS and above) involves multiple rounds of collision and ion extraction, and is usually carried out in ion trap or ion cyclotron resonance instruments, which have ion storage and selection capability. Multidimensional MS is particularly useful where the analyte is very complex, where ionization produces relatively few structurally diagnostic ions, or where useful ions are obscured or suppressed by others... 

FT-MS is an ion cyclotron resonance instrument in which trapped ions are excited rapidly and detected simultaneously using Fourier transform techniques [33]. The term FT-ICR is also used. The ICR is a device to determine the mass-to-charge ratio of an ion by measuring its cyclotron frequency. The advantages of FT-MS are accurate mass determination (sub-ppm) with very high resolution (tens of thousands or even millions), high sensitivity (sub-femtomole) and multistage capability [34]. 

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