Mass analyzers, electrostatic

The direct imaging magnetic sector mass analyzer (Fig. 3.19) has the unique property that all parts (lenses, electrostatic analyzer and magnetic sector field) of the secondary ion optics are stigmatic (comparable with light microscopes). This means that all points of the surface are simultaneously projected into the analyzer. 

The Orbitrap. The Orbitrap analyzer, [26] invented by Alexander Makarov, has been defined by the company that commercially produces it as the first totally new mass analyzer to be introduced to the market in more than 20 years . Its name recalls the concept of trapping ions. Indeed, ions are trapped in an electrostatic field produced by two electrodes a central spindle-shaped and an outer barrel-like electrode. Ions are moving in harmonic, complex spiral-like movements around the central electrode while shuttling back and forth over its long axis in harmonic motion with frequencies... 

Thermospray (TSP) [29-31] unites three modes of operation. In pure TSP, a solution of the analyte and a volatile buffer, usually 0.1 M ammonium acetate, is evaporated from a heated capillary at a flow rate of 1-2 ml min into a heated chamber, hence the term thermospray. As the solvent evaporates, the analyte is forming adducts with ions from the buffer salt. While most of the neutrals are removed by a vacuum pump, the ions are extracted orthogonally from their main axis of motion by use of an electrostatic potential. The ions are transferred into a quadrupole mass analyzer through a pinhole of about 25 pm in diameter (Fig. 11.2). The quadrupole was employed according to its tolerance to poor vac-... 

Figure 4 The Electrospray Ionization Source Generates Ions via Charged Droplet Evaporation Followed by Electrostatic Direction of the Ions into a Mass Analyzer...

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-... 

Droplets in the aerosol shrink as the solvent evaporates, thereby concentrating the charged sample ions. When the electrostatic repulsion among the charged sample ions reaches a critical point, the droplet undergoes a so-called Coulombic explosion, which releases the sample ions into the vapor phase. The vapor phase ions are focused with a number of sampling orifices into the mass analyzer. 

Fig. 1. MALDI and electrospray processes are represented schematically. Electrospray ionization involves the formation of charged droplets, while MALDI occurs through the laser evaporation from a crystallized sample/matrix mixture. In both techniques, the sample ions are extracted and transmitted through electrostatic lenses to a mass analyzer...

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