Transmission electrostatic analyzer

The secondary Ion extraction optics should Include an Immersion lens above the sample surface to maximize secondary Ion transmission from the sample surface to the mass spectrometer. An electrostatic analyzer should again be used to filter out high-energy neutral particles and photons from the secondary Ion beam. Energy analysis of the secondary Ions Is generally not necessary, but can be used to vary the amount of fragmentation observed In the mass spectrum (9). 

After post-ionization in the 3 cm long cylindrical plasma space between sample surface and the opposite wall, SN" enter a 90° electrostatic ion energy analyzer (ion optics) suppressing ionized plasma gas particles to a degree of 10 -10 noise levels are correspondingly low (1 cps). The transmission of the electrostatic ion optics is in the range of a few per cent. 

Magnetic analyzers are often used in various combinations with electrostatic sectors. Sector instruments are characterized by good ion transmission. Depending on the order of these analyzers, very high resolution and wide mass ranges can be achieved. Sector instruments suffer from a relatively low scan rate, which makes their application in GC-MS and LC-MS studies somewhat limited. At the same time, some types of tandem mass spectrometry experiments with mass-selected ions can be performed only on this type of equipment. 

MALDI-TOF MS is by far the fastest and also the most sensitive of all MS techniques available for the analysis of peptides and small proteins, due to the very short analysis times (fractions of a millisecond) and high ion transmission of TOF MS. In addition, it is not limited to the analysis of peptides, as are all currently available combinations of MALDI with FT-ICR MS, electrostatic ion traps, or quadrupole analyzers due to their limited m/z range. This hmitation does not apply to ESI, which in contrast to MALDI delivers large molecules exclusively as highly charged molecular ions. 

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