Mass analyser, magnetic

Magnetic mass analyser. Where high mass resolution is a requirement in the SIMS experiment, then the traditional magnetic-sector analyser may be utilised. Presently, however, these magnetic mass analysers are used in the DSIMS mode of characterisation. The transmission of secondary ions is much higher than in the quadrupole system, approximately 1%. Due to its lack of usage within the SSIMS area it will not be described further. 

A magnetic mass analyser is considerably more expensive and physically larger than its quadrupole counterpart. In normal operation the ion source operates at a high positive voltage, so that the monochromator interface region must be carefully designed to ensure that photoelectrons ejected from either the photodetector or any metal surfaces are not accelerated into the ion source to produce spurious ionization. For maximum ion transmission it is necessary to use an ion-optical lens, such as an electrostatic quadrupole, to focus the ions from a wide area into the narrow entrance slit of the mass spectrometer. The magnetic mass spectrometer, unlike a quadrupole... 

The operation of this type of device is fundamentally different to those described previously in which ions of one m/z ratio at a time enter the mass analyser. By varying the conditions in the mass analyser, e.g. magnetic field, quadrupole field, etc., ions of different m/z values are brought to the detector and a corresponding mass spectrum obtained. 

Double-focusing mass spectrometer A mass spectrometer consisting of electrostatic and magnetic sector analysers capable of achieving high-mass spectral resolution. 

Hybrid mass spectrometer An MS-MS instrument combining magnetic sector and quadrupole mass analysers. 

Magnetic sector A low-resolution mass analyser in which the variation of a magnetic field is used to bring ions of different m/z ratios to a detector. 

Walder AJ, Freedman PA (1992) Isotopic ratio measurement using a double focusing magnetic sector mass analyser with an inductively coupled plasma as an ion somce. J Anal At Spectrom 7 571-575... 

Various tandem MS instrument configurations have been developed, e.g. sector instruments, such as CBCE, CBCECB or CECBCE, and hybrid instruments, e.g. BCECQQ (B = magnetic sector analyser, E = electrostatic analyser, C = collision cell, Q = quadrupole mass spectrometer), all with specific performance. Sector mass spectrometers have been reviewed [168],... 

Figure 4.4. Illustrating the operation of a magnetic sector mass analyser.

DHN) have been characterized by both mass spectroscopy and ll nuclear magnetic resonance analyses as trans-2-geranyl 1,6-DHN and //m.v-5-gcranyl 1,6-DHN with a yield ratio of 10 1. 

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. 

Mass analysis is simply a method of separating ions of different mass-to-charge ratio (m/z). However, since the ions of interest are almost exclusively singly charged, then m /z is equivalent to mass for practical purposes. There are two types of mass analyser commonly employed for ICP-MS, namely the quadrupole and the magnetic sector. 

Q. What are the advantages and disadvantages of magnetic sector mass analysers compared with quadrupoles ... 

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