Novel ion traps using planar resistive electrodes: Implications for miniaturized mass analyzers

Abstract

In radiofrequency ion traps, electric fields are produced by applying time-varying potentials between machined metal electrodes. The electrode shape constitutes a boundary condition and defines the field shape. This paper presents a new approach to making ion traps in which the electrodes consist of two ceramic discs, the facing surfaces of which are lithographically imprinted with sets of concentric metal rings and overlaid with a resistive material. A radial potential function can be applied to the resistive material such that the potential between the plates is quadrupolar, and ions are trapped between the plates. The electric field is independent of geometry and can be optimized electronically. The trap can produce any trapping field geometry, including both a toroidal trapping geometry and the traditional Paul-trap field. Dimensionally smaller ion trajectories, as would be produced in a miniaturized ion trap, can be achieved by increasing the potential gradient on the resistive material and operating the trap at higher frequency, rather than by making any physical changes to the trap or the electrodes. Obstacles to miniaturization of ion traps, such as fabrication tolerances, surface smoothness, electrode alignment, limited access for ionization or ion injection, and small trapping volume are addressed using this design. analysis is accomplished using radiofrequency quadrupolar potentials in at least two dimensions. In the Paul trap, three hyperboloidal electrodes trap ions in all three dimensions. In the rectilinear and linear traps, DC potentials on end plates trap ions in the third dimension. In the toroidal ion trap, the two-dimensional trapping field forms a closed loop.In all ion trap variations, metal electrodes are used to produce the appropriate electric fields. For full-sized ion traps, modem machining equipment easily produces the hyperboloidal electrode surfaces of the quadrupole ion trap. For miniaturized traps, however, machining methods have been pushed to the limit, and simpler electrode geometries such as planar and cylindrical are required. For this reason, most miniaturized and microfabricated ion traps have utilized the cylindrical trap design [12,[16][17][18][19][20].The need for a portable mass spectrometer has largely driven efforts to produce miniaturized ion traps [21]. Although the mass analyzer is just one of several components of a complete mass spectrometer system, miniaturization of the mass analyzer can often reduce the size and weight of other components. For example, the amplitude of ion motion is reduced in a small ion trap, so the mean free path of ions can be smaller (or

What can we learn from ambient ionization techniques?

“…Another fascinating development that took place in parallel was the development of portable or miniaturized mass spectrometers [9 -14]. An entire issue of this journal [JASMS 2008, 19(10)] has been devoted to this topic under the heading "Harsh Environment Mass Spectrometry" [12,13,[15][16][17][18][19][20][21][22]. Although all of the field-portable mass spectrometers available nowadays are less powerful in terms of sensitivity, mass range, and mass resolving power than their laboratory-based counterparts, the vision is clearly to combine suitable atmospheric pressure sources with portable mass spectrometers to run analyses in subway systems, airports, at sports events, in restaurants, supermarkets, wholesale markets, and perhaps in the future even in the average home.…”

Miniaturized High-Resolution Time-of-Flight Mass Spectrometer MULTUM-S II with an Infinite Flight Path

“…In fact, almost all commercialized miniature instruments have adopted ion traps and QMF. [13][14][15] In addition, it can be noted that there is a large variety of ion traps: (1) three dimensional hyperbolic ion traps, (2) rectilinear ion traps, [16][17][18][19] (3) toroidal ion traps, 20 (4) planar electrode (Halo) ion traps, [21][22][23] and (5) cylindrical ion traps. [24][25][26][27][28][29][30][31] The main reasons for choosing ion traps for portable instruments are that ion traps provide a relaxed vacuum condition, low power consumption, inherent tandem mass spectrometry capability, and easily miniaturized geometry for weight saving.…”

Miniaturized Mass Spectrometer in Analysis of Greenhouse Gases: The Performance and Possibilities

“…In fact, almost all commercialized miniature mass spectrometers, for example Guardion-7 (Lammert et al, 2006) and Griffin Analytical 600 in Table 1, have adopted ion traps and QMF. In addition, it can be noted that there is a large variety of ion traps: (1) three dimensional hyperbolic ion traps, (2) rectilinear ion traps (Liang et al, 2008;Fico et al, 2009;Li et al, 2009;Ouyang et al, 2009), (3) toroidal ion traps (Lammert et al, 2006), (4) planar electrode ion traps (Austin et al, 2007;Austin et al, 2008;Yang et al, 2008), and (5) cylindrical ion traps (Van Amerom et al, 2008;Wells et al, 2008;Chaudhary et al, 2009). …”