Electrostatic mass spectrometric analyzers

Figure 2.1 Mass spectrometric approach. Dl, direct inlet GC, gas chromatography HPLC, high performance liquid chromatography CZE, capillary zone electrophoresis El, electron ionization Cl, chemical ionization ESI, electrospray ionization DESI, desorption electrospray ionization APCI, atmospheric pressure chemical ionization MALDI, matrix assisted laser desorption ionization B, magnetic analyzer E, electrostatic analyzer...

A second important property of mass spectrometric separation systems is the abundance sensitivity. Even under sufficient vacuum conditions there is a scattering of ions in the beam by the residual gas. Furthermore, by scattering of particles by the wall of the analyzer tube or by electrostatic repulsion in the ion beam itself or charging effects, so-called peak tails in mass spectra are observed, which result in an increasing energy spread of ions and consequently in a deterioration in the abundance sensitivity. The abundance sensitivity of a mass spectrometer is defined as ... 

For the mass spectrometric analysis of peptides, the two ionization techniques are similarly complementary as they are for proteins [38]. Today, most mass spectrometers equipped with an ESI or a MALDI source provide the possibility of isolating analyte ions on the basis of their m/z ratio and, by different activation methods, transfer energy to them which results in their decomposition. Mass analysis of the resulting fragment ions can provide detailed structural information and is termed tandem-MS or MS/MS analysis (Fig. 2). Electrostatic ion traps and FT-ICR analyzers also provide multiple stages of ion isolation and fragmentation experiments (MS ), of which MS is especially useful for protein identification and modification analyses. 

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