Mass Analysis in Fourier Transform Ion Cyclotron Resonance Instruments

6 Mass Analysis in Fourier Transform Ion Cyclotron Resonance Instruments 

A Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR-MS) can be considered as an ion trap system, where the ions are trapped in the magnetic field rather than in a quadrapole electric field. The ICR cell is a cubic or cylindrical cell positioned in a strong magnetic field B (up to 15 T). The cell consists of two opposite trapping plates, two opposite excitation plates, and two opposite receiver plates (Fig. 4.6). Extreme high vacuum should be achieved in the cell, e.g., 10 mbar. 

An ion of mass m, with velocity v, and z elementary charges describes a circle of radins r, perpendicular to and around the magnetic field lines. The resulting cyclotron frequency m can be written as  

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