The Double-Focusing and Tri-Sector Mass Analysers

One of the major reasons why ions with similar m/z ratios cannot be resolved is that they are not all formed at exactly the same place in the source of the 

The double-focusing mass spectrometer consists of both magnetic sector and electrostatic analysers (ESAs), the latter being a device which focuses ions with the same m /z values but differing energies. The extent to which the beams of ions of closely similar m /z ratios overlap is thus reduced so that in many cases they may be separated. This then allows their m/z ratios to be determined with more accuracy and precision and the atomic composition of the ion to be determined. 

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Beside the most commonly used ion separation systems, such as the quadrupole mass analyser, the ion-trap mass analyser and the double-focusing and tri-sector mass analyser, a new system has encountered increasing interest. This system, the time-of-flight (TOP) mass analyser offers fast scanning opportunities coupled with the possibility of detecting ions with high m/z ratios. This provides a useful tool for rapid quality control of sensorial profiles as well as the detection and identification of toxins and proteins or protein-bound substances [42]. 

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