Halo Ion Trap Mass Spectrometer

Abstract

We describe a novel radio frequency ion trap mass analyzer based on toroidal trapping geometry and microfabrication technology. The device, called the halo ion trap, consists of two parallel ceramic plates, the facing surfaces of which are imprinted with sets of concentric ring electrodes. Radii of the imprinted rings range from 5 to 12 mm, and the spacing between the plates is 4 mm. Unlike conventional ion traps, in which hyperbolic metal electrodes establish equipotential boundary conditions, electric fields in the halo ion trap are established by applying different radio frequency potentials to each ring. The potential on each ring can be independently optimized to provide the best trapping field. The halo ion trap features an open structure, allowing easy access for in situ ionization. The toroidal geometry provides a large trapping and analyzing volume, increasing the number of ions that can be stored and reducing the effects of space-charge on mass analysis. Preliminary mass spectra show resolution (m/Deltam) of 60-75 when the trap is operated at 1.9 MHz and 500 Vp-p.

Experimental Characterization of Secular Frequency Scanning in Ion Trap Mass Spectrometers

“…Welling and co-workers used this method, which they termed "secular scanning", to obtain higher resolution mass spectra when compared to q scanning in a linear ion trap (the resonance was quadrupolar over a limited mass range and with slow frequency scanning) [27], Roth and coworkers used secular frequency scanning in a linear trap for mass selective excitation [28], and the Austin group at Brigham Young University used it to scan ions out of the halo ion trap [29][30][31]. Note that in the case of the halo trap, the geometry of the device necessitated the use of AC frequency scanning because simulations indicated that a conventional rf amplitude ramp would cause ions to collide with the electrodes and ceramic holders instead of being ejected out the apertures in the electrodes.…”

Hand-portable gas chromatograph-toroidal ion trap mass spectrometer (GC-TMS) for detection of hazardous compounds

“…Major efforts have been made to miniaturize capillary GC [10 -14] and most MS analyzers, including time-of-flight (TOF) [15][16][17], quadrupole [18], magnetic sector [17][18][19], Fourier transform ion cyclotron resonance (FTICR) [20], and cylindrical [21][22][23], rectilinear [24 -26], and toroidal [27,28] ion traps. Most of these reports have concentrated on miniaturizing the GC column or the mass analyzer.…”

“…One limitation to miniaturizing ion traps is reduction in ion storage capacity. However, this reduction can be ameliorated by trapping ions in a toroidal geometry [27,28,39].…”

Performance Evaluation of a Loeb-Eiber Mass Filter at 1 Torr

“…The simplified geometry of a cylindrical ion trap in comparison to 3D ion traps has led to a significant research investment in the miniaturization of ion traps [21][22][23][24][25][26] and micro-fabricated ion trap arrays [27][28][29]. Lammert [30,31] and Austin [32][33][34] have studied toroidal ion traps of various geometries in an attempt to expand the quantitative dynamic range of ion traps in miniature and portable instruments.…”