Distance-of-Flight Mass Spectrometry: A New Paradigm for Mass Separation and Detection

Abstract

Distance-of-flight mass spectrometry (DOFMS) offers the advantages of physical separation of ions, array detection of ions, focusing of initial ion energy, great simplicity, and a truly unlimited mass range. DOFMS instrumentation is similar to that of time-of-flight mass spectrometry (TOFMS) and shares its ion-source versatility, batch analysis, and rapid spectral-generation rate. With constant-momentum ion acceleration and an ion mirror, there is a time at which ions of all mass-to-charge values are energy focused at their particular distances along the flight path. A pulsed field orthogonal to the flight path drives the ions to reach the detector array at this specific time. Results from a 0.29-m proof-of-principle instrument verify the theoretically predicted energy focus and demonstrate how the range of mass-to-charge values that impinge on the detector array can be readily changed. DOFMS could be combined sequentially with TOFMS to enable simultaneous scanless tandem mass spectrometry.

Distance-of-Flight Mass Spectrometry with IonCCD Detection and an Inductively Coupled Plasma Source

“…Ions are then accelerated into the field-free mass-separation region by means of a CMA pulse applied across the 10-cm orthogonal acceleration region [7]. The characteristics of a CMA pulse have been detailed elsewhere [1][2][3][4][5][6][7][8][9]25]; of primary importance is that the pulse needs to be shorter in duration than the time ions of interest spend in the orthogonal acceleration region (hereafter referred to as the CMA region). Typically, the CMA pulse is +1 kV and 2-7 μs in duration (depending on the mass range of interest).…”

“…ince the development of distance-of-flight mass spectrometry (DOFMS) theory by Enke and Dobson [1], several papers have shown its experimental viability [2][3][4][5][6][7][8][9]. Conceptually, mass-to-charge (m/z) separation in DOFMS is similar to that in time-of-flight mass spectrometry (TOFMS), while the ion detection process resembles that of spatially dispersive, sectorfield mass spectrometry (SFMS).…”

“…Earlier work on DOFMS was conducted with two alternative ion detectors employed in the same instrument [9]: a microchannel plate-phosphor screen (MCP/phosphor) combination [2,[5][6][7] and a multichannel focal plane camera (FPC) [3,4]. The MCP/phosphor assembly has a 4.0-cm active length [2] and, in combination with a CCD camera, provides a linear dynamic range (LDR) of five orders of magnitude [5] and a full-width at half-maximum mass resolving power (RP FWHM ) of approximately 500 [6].…”

Inductively Coupled Plasma Zoom–Time-of-Flight Mass Spectrometry

“…The concept of space-focusing in CEA-TOFMS is well established as is the use of a reflectron to mirror the space focus and to partially compensate for ionenergy disparities [23]. The concept of energy-focused CMA was introduced in 2007 [24] and has been applied to both distance-of-flight MS (DOFMS) [25][26][27][28][29][30][31] and TOFMS [22,32,33].…”

Radiofrequency pulsed glow discharge-ToFMS depth profiling of a CdTe solar cell: A comparative study versus time of flight secondary ion mass spectrometry

“…30,31 GD-based techniques can be applied to a variety of materials; both conducting and insulating materials can be analyzed using radiofrequency (rf) power. Multielemental, high depth resolution, analysis benefits from mass analyzers such as the time of flight mass spectrometer (ToFMS) 24 or the distance-of-flight mass spectrometer (DoFMS), 33,34 which are able to rapidly acquire complete mass spectra (and not just analyze a few user selected species) with high accuracy and sensitivity. GDs have been successfully coupled to different types of mass analyzers for both bulk and depth profile analysis.…”