FT-ICR mass analyzer is the most complex and difficult to operate. It offers the highest resolution, mass accuracy, and sensitivity.

FTMS is based on the principle of monitoring a charged particle’s orbiting motion in a magnetic field. While ions are orbiting, a pulsed RF signal is used to excite them. This allows the ions to produce detectable image current by bringing them into coherent motion and enlarging the radius of the orbit. The image current can generated by the ions can then be Fourier-transformed to obtain component frequencies of different ions, which correspond to their m/z. All ions with the same m/z value will orbit with the same cyclotron frequency in a uniform magnetic field. Since frequencies can be obtained at high accuracy, m/z can also be determined at high accuracy. In addition to high resolution, FTMS offers the ability to perform MSn. It is capable of ejecting all but the ions of interest.

Unlike double sector instruments, FT-ICR does not suffer from loss of sensitivity at high resolutions.