Ion trap mass analyser

In its most commonly encountered form, the ion trap mass spectrometer is a low-resolution instrument used in dedicated GC— MS systems. Ions introduced into an electrostatic ion trap mass spectrometer perform stable oscillations within a cavity bounded by two hemispherical electrodes and one ring electrode. Ramping the potentials applied to the electrodes causes the oscillations to become unstable and the ions are fiung out of the trap in mass (m/e) order. 

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Figure 3.5 Schematic of a (quadrupole) ion-trap mass analyser. From applications literature published by Thermofinnigan, Hemel Hempstead, UK, and reproduced with permission.

Figure 9.3 Schematic of (a) time-of-flight and (b) an ion-trap mass analyser. (Adapted from Sheehan, Physical Biochemistry, 2000).

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]. 

Figure 2.39 Schematic diagram of an ion trap mass analyser (Figure used by kind permission...

Figure 9.10 Schematic of an Ion Trap Mass Analyser. Ion traps work on a similar principle to quadrupole analysers, but here the trap acts as a three-dimensional capture box that releases ions when the potential and m/z are such that the analyte ion has a field-free path to the detector.

Fig. 3.4. Ion trap mass analyser. Ions of a broad distribution of m/z values are stored in the trap by application of radio frequency voltages to the end caps and ring electrode. A mass spectrum is obtained by increasing the magnitude of the radio frequency between the end caps so that the motions of selected ions become unstable and they are ejected.

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