Quadrupole magnetic trap

One direct way to close the chaimel whereby atoms escape from the central region of a quadrupole magnetic trap is to displace the potential (Fig. 6.9(a)) in the symmetry... 

In an experiment by Davis et al. (1995), an MOT was loaded with sodium atoms. In the final stage, the atoms were stored in a quadrupole magnetic trap. To suppress Majorana spin transitions near the centre of the trap, a far-off-resonance laser beam was used to plug the hole. Subsequent to evaporative cooling, some 5 x 10 atoms cooled down to a temperature of around 2 pK at a density of 4 x 10 cm . 

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. 

Almost any type of analyzer could be used to separate isotopes, so their ratios of abundances can be measured. In practice, the type of analyzer employed will depend on the resolution needed to differentiate among a range of isotopes. When the isotopes are locked into multielement ions, it becomes difficult to separate all of the possible isotopes. For example, an ion of composition CgHijOj will actually consist of many compositions if all of the isotopes ( C, C, H, H, 0, O, and 0) are considered. To resolve all of these isotopic compositions before measurement of their abundances is difficult. For low-molecular-mass ions (HjO, COj) or for atomic ions (Ca, Cl), the problems are not so severe. Therefore, most accurate isotope ratio measurements are made on low-molecular-mass species, and resolution of these even with simple analyzers is not difficult. The most widely used analyzers are based on magnets, quadrupoles, ion traps, and time-of-flight instruments. 

Different mass analysers can be combined with the electrospray ionization source to effect analysis. These include magnetic sector analysers, quadrupole filter (Q), quadrupole ion trap (QIT), time of flight (TOF), and more recently the Fourrier transform ion cyclotron resonance (FTICR) mass analysers. Tandem mass spectrometry can also be effected by combining one or more mass analysers in tandem, as in a triple quadrupole or a QTOF. The first analyzer is usually used as a mass filter to select parent ions that can be fragmented and analyzed by subsequent analysers. 

The operation of magnetic sector (Chap. 4.3), linear quadrupole (Chap. 4.4), or quadrupole ion trap (Chap. 4.5) mass spectrometers in the repetitive scanning mode is useful for the identification of the components of a mixture. If quantitation is a major issue (below), selected ion monitoring (SIM) is preferably employed the term multiple ion detection (MID) and some others are also in use. [33] In the SIM mode, the mass analyzer is operated in a way that it alternately acquires only the ionic masses of interest, i.e. it jumps from one m/z value to the next. [34-39] The information obtained from a SIM trace is equivalent to that from a RIC, but no mass spectra are recorded. Thus, the scan time spent on a diagnostically useless m/z range is almost reduced to zero, whereas the detector time for the ions of interest is increased by a factor of 10-100. [40] An analogous improvement in sensitivity (Chap. 5.2.3) is also observed. 

The most commonly used mass separators are quadrupoles, ions traps and time-of-flight analyzers, for which the principle of mass separation is discussed below. Additionally, other types such as magnetic sector field or Fourier-trans-form cyclotron-resonance instruments are available. 

Quadrupole Magnetic sector field Electric sector field Time of flight (ToF) Electrical Ion-trap Magnetic Ion-trap... 

MALDI-Fourier transform ion cyclotron resonance mass spectrometry MALDI-Q-ion mobility-TOFMS MALDI-Quadrupole-ion-trap-TOF mass spectrometry MALDI-TOF-imaging mass spectrometry MALDI Time-of-flight mass spectrometry Magnetic resonance imaging Matrix solution fixation Moxifloxacin... 

No one single mass analyzer is suitable for all applications and the choice of instrument is determined by the type of problem under investigation [68]. Double focusing magnetic/electrostatic sectorfield-, quadrupole-, quadrupole ion trap-, time-... 

Mass spectrometers (MSs) are classified by the technology they use to separate ionic masses into clusters. Their examples include the quadrupole, magnetic sector, time-of-flight, and ion-trap mass spectrometers. 

Electric sector Magnetic sector Quadrupole Ion trap Time-of-flight... 

Two peaks are considered to be resolved if the valley between them is equal to 10 % of the weaker peak intensity when using magnetic or ion cyclotron resonance (ICR) instruments and 50 % when using quadrupoles, ion trap, TOF, and so on. If Am is the smallest mass difference for which two peaks with masses m and m + Am are resolved, the definition of the resolving power R is R = ml Am. Therefore, a greater resolving power corresponds to the increased ability to distinguish ions with a smaller mass difference. 

Quadrupole Ion trap TOF TOF reflectron Magnetic FTICR Orbitrap... 

---