First inductively coupled plasma-distance-of-flight mass spectrometer: instrument performance with a microchannel plate/phosphor imaging detector

Abstract

Here we describe the first combination of a Distance-of-Flight Mass Spectrometry (DOFMS) instrument and an inductively coupled plasma (ICP) ion source. DOFMS is a velocity-based MS technique in which ions of a range of mass-to-charge (m/z) values are detected simultaneously along the length of a spatially selective detector. As a relative of time-of-flight (TOF) MS, DOFMS leverages benefits from both TOFMS and spatially dispersive MS. The simultaneous detection of groups of m/z values improves dynamic range by spreading ion signal across many detector elements and reduces correlated noise by signal ratioing. To ascertain the performance characteristics of the ICP-DOFMS instrument, we have employed a microchannel-plate/ phosphor detection assembly with a scientific CCD to capture images of the phosphor plate. With this simple (and commercially available) detection scheme, elemental detection limits from 2-30 ng L À1 and a linear dynamic range of 5 orders of magnitude (10-10 6 ng L À1 ) have been demonstrated.Additionally, a competitive isotope-ratio precision of 0.1% RSD has been achieved with only a 6 s signal integration period. In addition to first figures of merit, this paper outlines technical considerations for the design of the ICP-DOFMS.

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

“…Supplementary Figure S-1 and Figure 4) is approximately -0.5, indicating that the isotoperatio precision is shot-noise limited. Overall, these results are consistent with previous studies of ICP-TOFMS instruments [38,39] and with a DOFMS study on the same instrument platform with the same ICP source [29].…”

“…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].…”

“…Once nebulized, the sample solutions entered the ICP as an aerosol, where they were atomized and ionized, and the resulting species entered the three-stage differentially pumped vacuum interface. The vacuum interface has been described elsewhere [26,29]. The pressures were approximately 0.7 Torr, 0.5 mTorr, and 0.7 μTorr in each of the three vacuum stages, respectively.…”

“…The 40.68 MHz ICP ionization source (crystal-controlled, model HF 2000F; PlasmaTherm Inc., Kresson, NJ, USA) used in this study has been previously described in detail [29,30]. Commercially available analytical reagent grade 1000 ppm stock solutions or analytical reagent grade nitrate salts (from several different manufacturers) were used to prepare all sample and standard solutions.…”

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

“…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).…”