Digital ion trap

The ITs described in Section 2.3.2 operate with a sinusoidal electrical field in the rf region (Frf) and the ions are ejected from the trap by increasing the VTi value. 

However, the Mathieu parameters a and q, defined by Eqs. 2.9 and 2.10, can still be employed for the description of the DIT theoretical stability diagram, considering the U and V values as the average values of the dc and ac components of the rectangular wave voltage applied to the intermediate electrode. They are defined as 

As shown in Fig. 2.23, the duty cycle d is described as the ratio between x and the total period T of the rectangular wave. Unlike the sinusoidal wave, the rectangular wave can be generated with different pulsing times for Fi and V2 produced by the digital circuitry. In a DIT, the az value is a function of both the dc offset and the duty cycle d. In fact, the dc component U can be generated either by an imbalance between Vi and V2 or by variation of the duty cycle d. 

For ITs driven by a sinusoidal waveform, the superimposition of a dc potential (U) on the main trapping field (Frf) requires the use of an additional dc power supply. However, in the DIT, the dc component can be generated easily by varying the duty cycle of the rectangular waveform through appropriate variation of the parameter values entered into the control software of the mass spectrometer. 

With this approach, first the V values (usually 103V) are lower than that employed in QIT (usually in the 104V range) second the ions are ejected from the trap by scanning the rectangular wave frequency. 

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Ding, L., Sudakov, M., Brancia, F.L., Giles, R., and Kumashiro, S. (2004). A digital ion trap mass spectrometer coupled with atmospheric pressure ion source, J Mass Spectrom., 39,471 148. 

Digital ion trap 64,85 Digital waveform 65 Double-focusing mass analyzers 47 Double-focusing mass spectrometers 50 Dried droplet method 39 Droplet radius 18... 

See also Volume 4, Ch ter 4 Rectangular Waveform Driven Digital Ion Trap (DIT) Mass Spectrometer Theory and Applications by Francesco Brancia. 

FIGURE 12.5 Definition of the dnty cycle, d, in relation to the operation of the digital ion trap. 

FIGURE 12.6 A typical scan table for a forward mass scan of the digital ion trap. 

Identification of the Ions and Their Charge States Used in the Experimental Determination of the Boundaries of the Stability Diagram for the Digital Ion Trap (DIT)... 

Ding, L. Sudakov, M. Kumashiro, S. A simulation study of the digital ion trap mass spectrometer. Int. J. Mass Spectrvm. 2002, 221, 117-138. 

Ding, L. Brancia, F. L. Electron capture dissociation in a digital ion trap mass spectrometer. Anal. Chem. 2006, 78, 1995-2000. 

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