Orbital trapping

Orbital trapping mass spectrometers achieve resolutions of up to 105 and would be the next choice after ToF mass spectrometers if resolving powers above 104 are required. In addition to mass resolution, the selectivity of an MS can be critical to distinguish between co-eluting and not mass-resolved compounds. For example, typical triple-quad mass spectrometers usually cannot achieve better than unit-mass resolution. However, special operation modes like neutral loss scans and precursor ion scans can filter out compounds of interest even if neither LC separations nor MS scans would be sufficient to resolve these compounds (note that this is a filtering step). 

A. Makarov. Electrostatic Axially Harmonic Orbital Trapping A High-Performance Technique of Mass Analysis. Anal. Chem., 72(2000) 1156-1162. 

Electrostatic axially harmonic orbital trapping, 15 662-663 Electrostatic discharge-protection circuits, for LEDs, 14 863... 

Makarov, A. Electrostatic axially harmonic orbital trapping a high-performance technique of mass analysis. Anal. Chem. 2000, 72, 1156-1162. 

Figure 3.18. Bottleneck in the predissodation of Helj (a) orbits trapped within the cantori created by the nonlinear resonance and (b) orbits trapped between the cantori and the separatrix. [Reprinted with permission from M. J. Davis and S. K. Gray, J. Chem. Phys., Vol. 84 (1986), p. 5389. Copyright 1986, American Institute of Physics.]...

Besides TOP instruments, other mass analyzers such as quadrapole-orthogonal TOP instruments, ion traps, Pourier transform (PT) ion cyclotron resonance mass spectrometers and, most recently, orbital trapping mass spectrometers were employed for MALDI imaging in microprobe mode, as described later in this chapter (see also Chapter 2). 

Figure 4.10 High-resolution atmospheric pressure-MALDI images of a mouse urinary bladder tissue section, obtained on an orbital trapping mass spectrometer with 10pm step size. Two phospholipid signals closely neighboring in mass were imaged showing...

Only a few applications of orbital-trap (orbitrap) high-resolution mass spectrometers have been reported for STA or GUS so far. For the detection of 29 doping agents, an LTQ-orbitrap mass spectrometer equipped with an APCI ion source was used with insource CID and acquisition in the positive ionization scan mode from 100 to 500 Da (35). The mass resolution of60,000 fiill width at half maximum (FWHM) ensured a precision better than 2 ppm (using external calibration), while the limit of detection was better... 

The Kingdon trap, an ion trapping device that consists of an outer barrel-like electrode and a coaxial inner spindle-like electrode that form an electrostatic field with quadro-logarithmic potential distribution. The frequency of harmonic oscillations of the orbitally trapped ions along the axis of the electrostatic field is independent of the ion velocity and is inversely proportional to the square root of m/z so that the trap can be operated as a mass analyser using image current detection and Fourier transformation of the time domain signal. 

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