Novel linear ion trap mass analyzer composed of four planar electrodes

Abstract

A novel linear ion trap mass analyzer was developed using just four elongated planar electrodes, mounted in parallel, and employing an RF potential for ion trapping in the radial and axial directions. Mass analysis was achieved using the mass-selective instability scan with ion ejection in the radial direction. The performance of this new device was characterized in comparison with the 6-electrode rectilinear ion trap (RIT) from which it is derived. The 4-electrode trap gives optimum performance in an asymmetric geometry, just like the original optimized 6-electrode RIT. The strong RF fringing fields at the ends of the RF rods account for axial ion trapping without use of extra electrodes or an axial DC voltage. Field calculations and simulations have been carried out to study the trapping potential inside RITs with various configurations. Demonstrated capabilities include analysis of externally injected ions with mass resolution in excess of 1000 and a mass/charge range of 650 Th as well as tandem mass spectrometry capabilities. The geometric simplicity and performance characteristics of the 4-electrode RIT make it particularly attractive in the development of next generation miniaturized mass spectrometers.

Numerical observation of preferred directionality in ion ejection from stretched rectilinear ion traps

“…6 shows the stability region for the RIT-X (where the stretch is in the x-direction) on the U dc -V rf and a x -q x planes. This plot is in close agreement with the experimentally obtained stability boundary reported by Song et al [27] for their 6-electrode RIT.…”

“…For the RIT, Ouyang et al [19] and Zhang et al [32] have stretched the central section in one direction to obtain improved resolution in mass spectra for resonance ejection experiments. Similar results were reported in a stretched RIT in resonance ejection experiments by [27] using their 4-electrode RIT [26].…”

Extending the Ion Capacity of a Linear Ion Trap Using Nonlinear Radio Frequency Fields

“…Other methods involve increasing the ion cloud dimensions and the ejection speed by addition of nonlinear fields and/or multiple resonances [16,17]. Methods of forming additional higher order rf fields and resonance ion ejection in the presence of these fields have been extensively described in literature [18][19][20][21][22][23][24][25]. The most common methods are the ones that are comprised of mechanical modifications of the trap geometry [18,19,[21][22][23][24][25].…”

“…Methods of forming additional higher order rf fields and resonance ion ejection in the presence of these fields have been extensively described in literature [18][19][20][21][22][23][24][25]. The most common methods are the ones that are comprised of mechanical modifications of the trap geometry [18,19,[21][22][23][24][25]. These methods involve either changing the relative position of electrodes with respect to each other, while keeping the ideal hyperbolic shape of the electrodes, or modifying the shape of the electrodes.…”

Computer simulation of the gap-tripole ion trap with linear injection, 3D ion accumulation, and versatile packet ejection

“…For example, the four-electrode rectilinear ion trap (RIT) had an axial pseudopotential, however, its trapping efficiency was lower than a 6-electrode RIT with pulse DC in the z-electrodes [21,22]. Also, axial focusing DC fields have been created in the quadrupole LIT by mounting extra electrodes or decreasing the axial length [23,24].…”