Time-of-fiight, mass spectrometer

Langer and Gohlke (33) described the first modern coupling of EGA with mass spectrometry in 1963. They heated the sample, by means of a small furnace, in the vacuum chamber of a time-of-fiight mass spectrometer and recorded the mass spectra of the decomposition products at selected inter-... 

TOF (time-of-fiight) mass spectrometers are also increasing in popularity and have been successfully coupled with gas chromatographs. In fact, the first successful on-line identification of GG eflBiuents by MS was with a TOF (29). TOF spectrometers are sensitive instruments. They are by far the fastest scanning of the three major spectrometer types— 50,000 lines per second. This feature makes it the only mass analyzer available for fast reaction research. The TOF also has a stable mass scale and can be computerized readily. However, resolution and mass range of the TOF instrument are low—about 500 amu. This may limit its application for pesticide residue analysis however, mass spectra of organophos-... 

K. Ekroos, I. V. Chemushevich, K. Simons, and A. Shevchenko, Quantitative profiling of phospholipids by multiple precursor ion scanning on a hybrid quadrupole time-of-fiight mass spectrometer. Anal. Chem. 74, 941-949 (2002). 

Myers D. P., Li G., Yang P. and Hieetje G. M. (1994) An inductively coupled plasma time-of-fiight mass spectrometer for elemental analysis. Part 1 optimization and characterization, J Am Soc Mass Spectrom 5 1008-1016. 

Luca A, Schlemmer S, Cermak 1, Gerlich D. (2001) On the combination of a linear field free trap with a time-of-fiight mass spectrometer. Rev. Sci Instr. 72 2900-2908. 

See also Chemical Structure Information from Mass Spectrometry Chromatography-MS, Methods Fast Atom Bombardment Ionization in Mass Spectrometry Fragmentation In Mass Spectrometry Hyphenated Techniques, Applications of in Mass Spectrometry Medical Applications of Mass Spectrometry MS-MS and MS Nucieic Acids and Nucieotides Studied Using Mass Spectrometry Peptides and Proteins Studied Using Mass Spectrometry Quadrupoies, Use of in Mass Spectrometry Sector Mass Spectrometers Surface induced Dissociation in Mass Spectrometry Time of Fiight Mass Spectrometers. 

See also Fragmentation in Mass Spectrometry Gas Phase Appiications of NMR Spectroscopy ion Dissociation Kinetics, Mass Spectrometry ion Energetics in Mass Spectrometry Photoionization and Photodissociation Methods in Mass Spectrometry Time of Fiight Mass Spectrometers. 

Probably the simplest mass spectrometer is the time-of-fiight (TOP) instrument [36]. Aside from magnetic deflection instruments, these were among the first mass spectrometers developed. The mass range is theoretically infinite, though in practice there are upper limits that are governed by electronics and ion source considerations. In chemical physics and physical chemistry, TOP instniments often are operated at lower resolving power than analytical instniments. Because of their simplicity, they have been used in many spectroscopic apparatus as detectors for electrons and ions. Many of these teclmiques are included as chapters unto themselves in this book, and they will only be briefly described here. 

B. A. Mamyrin, V. I. Karataev, D. V. Shmikk, and V. A. Zagulin, Mass reflectron. New nonmagnetic time-of-fiight high-resolution mass spectrometer, Z. Eksp. Teoreticheskoi Fiz. 64 (1973), 82-89. 

Fig. 1 Schematic representation of a mass spectrometer depicting its main components and the different modes used. Abbreviations DIP direct insertion probe DEP direct exposure probe GC gas chromatography LC liquid chromatography CE capillary chromatography TEC thin-layer chromatography FEE field-flow fractionation APCI atmospheric pressure ionization El electron impact Cl chemical ionization FAB fast-atom bombardment PD plasma desorption MALDI matrix-assisted laser desorption ionization ED laser desorption TSP thermospray ESI electron spray ionization HSI hypherthermal surface ionization Q quadropole QQQ triple quadropole TOE time-of-fiight FTMS Fourier transform mass spectrometer IT ion trap EM electrom multiplier PM photomultiplier ICR ion cyclotron resonance.

Time-of-fiight instruments are configured as either a stand-alone TOF mass analyzer (TOF MS) or as a hybrid quadrupole time-of-fiight (QqTOF) mass spectrometer the latter consists of a quadmpole front-end and an orthogonal acceleration TOF back-end for MS/MS experiments (Fig. 6.10). The orthogonal design minimizes the ions initial velocity spread as they are accelerated into the TOF by a pulsed potential. A QqTOF can be operated as a TOF mass analyzer (QqTOF MS, full-scan) or a quadmpole TOF tandem mass spectrometer (QqTOF MS/MS, product ion scan). Compared to a TOF MS, the... 

Recently introduced tandem mass spectrometers, having both features, such as quad-rupole linear ion trap (QqLIT, LTQ or Q-trap), quadrupole time-of-fiight (QqTOF), LTQ-Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), and LTQ-Orbitrap, and so on, have allowed for the development of several new methods for acrylamide detection [107,108]. 

The study of electronically excited atoms and molecules by mass spectrometry is a relatively recent development. In mu mass spectrometer the fiight time of a molecule from entrance slit to ionization chamber is a few hundred microseconds, so that only those excited states whose transitions to lower electronic states are highly forbidden can be investigated. Since these metastable species are often readily destroyed by wall collisions, it is generally necessary to employ a collision-free sampling system. 

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