Abstract

Fourier transforms ion cyclotron resonance (FT-ICR) mass spectrometry method introduced by Alan Marshall and Melvin Comisarow in 1974 is based on the measurement of the frequency of ion rotation in the magnetic field—cyclotron frequency. Ion mass to charge (m/q) ratio is inversely proportional to the cyclotron frequency and it is possible to determine the m/q ratio if we know this frequency and the magnetic field strength B. Since introduction of FT-ICR until now this technique demonstrates the highest mass resolution and mass measurement accuracy. The main part of the FT-ICR spectrometer is a measuring cell which is a Penning trap1. In this cell ions get trapped by electric field in the direction along magnetic field vector and by magnetic field in perpendicular direction. By applying RF electric field containing resonant frequency in the plane of ion cyclotron motion we are exciting ion's synchronous cyclotron motion. Rotating ions induce image charges in detection electrodes resulting in the current in electrical circuit of a signal amplifier. In the process of analysis of complex mixtures such as oil and humic acids more than 106 ions can be trapped in the ion trap and their cyclotron frequencies can be measured simultaneously. The ion–ion interactions considerably influence the ion motion resulting in shifting measured frequencies and m/q values. Further improvement of the main FT-ICR characteristics such as mass resolution, mass accuracy and dynamic range could be promoted by deeper understanding of ion motion dynamics in ion traps taking into account ion–ion interactions.

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