Electric sector analyzer

After ions have been formed by El, they are examined for mass and abundance by the analyzer part of the mass spectrometer, which can incorporate magnetic sectors, electric sectors, qua-drupoles, time-of-flight tubes, and so on. The region in which the ions are first formed is called... 

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. 

The most common modes of operation for ms/ms systems include daughter scan, parent ion scan, neutral loss scan, and selected reaction monitoring. The mode chosen depends on the information required. Stmctural identification is generally obtained using daughter or parent ion scan. The mass analyzers commonly used in tandem systems include quadmpole, magnetic-sector, electric-sector, time-of-flight, and ion cyclotron resonance. Some instmments add a third analyzer such as the triple quadmpole ms (27). 

An accelerator mass spectrometer is not really just an instrument with another type of analyzer, but rather a system that utilizes magnetic/electric sectors to separate ion species. In fact, it can also be looked upon as an ion source. However, we felt it belonged best among the analyzers, because of the way it is utilized. 

Performance Parameters. Since the detector is often involved in the separation of isobars, normal mass analyzer resolution and mass accuracy do not really apply. The mass spectrometric resolution would be determined by the magnetic and electric sectors. Only atomic species are analyzed, so that sets the upper m/z... 

Magnetic sector field (B) Combination of magnetic (B) and electric sector fields (E) Quadrupole mass analyzer (Q) Time-of-flight mass analyzer (ToF)... 

Sector field analyzers are magnetic or electric sector fields or a combination of the two with ion focusing and separation properties used in static mass spectrometers. 

Sputtered tons are collected and their masses analyzed in a double-focusing mass spectrometer in which Ihe velocity dispersions of Ihe magnetic anil electric sectors are matched to permit Ihe acceptance of a wide range of initial energies of the sputtered ions. No entrance slit is used and the bombarded area is stigmatically focused directly onto the resolving slit. 

Reactant-ion energy analyzer. An electric sector or a retarding lens (or some combination of these) is generally employed to define the translational energy of the ion beam. 

TOF mass analyzers are based on bombardment by a pulse of electrons or photons to periodically produce positive ions. The pulses have frequencies between 10 and 50 kFIz. The generated ions are then accelerated by an electric sector (voltages from 103 to 104 V) at the same frequency as the ionizing bombardment but with a certain gap. The accelerated ions pass to a 1 m long analyzer rod, which is not subjected to an electrical or magnetic field. As all the ions have the same kinetic energy, their velocities along the analyzer rod must be inversely proportional to the m/z ratio. In this way, those ions with lower m/z ratios reach the detector first. The times to reach the detector (the TOF) are between 1 and 30 ps. 

There are several types of ionization sources [MALDI, ESI, FAB (fast atom bombardment), PD (Cf-252 plasma desorption), El (electron ionization), Cl (chemical ionization) etc.], different types of mass analyzers [combinations of magnetic and electric sectors, quadrupolar filters (Q) and ion traps (IT), time-of-flight (TOF) and FT-ICR] and different detectors, each with its own advantages and drawbacks. We describe herein only the systems that presently have widespread use for the study of biomolecules ESI coupled to a quadrupole (or triple quadrupole, QqQ) mass analyzer or an ion trap, the MALDI source with the linear or reflectron TOF analyzer, and the FT-ICR system which can be equipped with both ESI and MALDI sources. 

Besides a magnetic field, an electric sector field also influences the trajectory of the ions. An electric sector field analyzer as a section of the cylindrical condenser consists of two cylindrical... 

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