Ion cyclotron resonance analysers ICRMS

These mass spectrometers, not widely used, are rather rare compared to the previous ones. Basically a magnetic ion-trap, a ICRMS is able to ascertain the mass of ions with great precision. The mode of operation can be described in the following way  

at any given moment, there will be as many different frequencies of rotation as there are ions of different m/z ratio in the trap. 

The practical expression 16.18 gives the frequency v (in kHz) of an ion of mass m (Da) carrying a charge z in a field B (tesla). Mass analysis is achieved by measuring precisely the different frequencies of the ions. 

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