Field-ion spectrometry

Riegner et al. (1997) Quahtative evaluation of field ion spectrometry for chem. warfare agent detection. Proceedings of the 45th ASMS Conference on Mass Spectrometry and Allied Topics 473. 

After acceleration through an electric field, ions pass (drift) along a straight length of analyzer under vacuum and reach a detector after a time that depends on the square root of their m/z values. The mass spectrum is a record of the abundances of ions and the times (converted to m/z) they have taken to traverse the analyzer. TOP mass spectrometry is valuable for its fast response time, especially for substances of high mass that have been ionized or selected in pulses. 

In addition to the wet and optical spectrometric methods, which are often used to analyse elements present in very small proportions, there are also other techniques which can only be mentioned here. One is the method of mass spectrometry, in which the proportions of separate isotopes can be measured this can be linked to an instrument called a field-ion microscope, in which as we have seen individual atoms can be observed on a very sharp hemispherical needle tip through the mechanical action of a very intense electric field. Atoms which have been ionised and detached can then be analysed for isotopic mass. This has become a powerful device for both curiosity-driven and applied research. 

Field ion spectrometer The Revised Black Book Totalforsvarets forskningsinstitut, Sweden Forster resonance energy transfer Fourier transform mass spectrometry Full width, half maximum Guerrilla s arsenal Gas chromatography... 

The atom-probe field ion microscope is a device which combines an FIM, a probe-hole, and a mass spectrometer of single ion detection sensitivity. With this device, not only can the atomic structure of a surface be imaged with the same atomic resolution as with an FIM, but the chemical species of surface atoms of one s choice, chosen from the field ion image and the probe-hole, can also be identified one by one by mass spectrometry. In principle, any type of mass analyzer can be used as long as the overall detection efficiency of the mass analyzer, which includes the detection efficiency of the ion detector used and the transmission coefficient of the system, has to be close to unity. 

Early field ion emission studies of gas-surface interactions use field ionization mass spectrometry. Gas molecules are supplied continuously to the tip surface by a polarization force and by the hopping motion of the molecules on the tip surface and along the tip shank. These molecules are subsequently field ionized. The role of the emitter surface in chemical reactions is not transparent and has not been investigated in detail. Only in recent pulsed-laser stimulated field desorption studies with atom-probes are these questions addressed in detail. We now discuss briefly a preliminary study of reaction intermediates in NH3 formation in pulsed-laser stimulated field desorption of co-adsorbed hydrogen and nitrogen,... 

Electrophoresis, which is discussed in Chapter 26, is the migration of ions in solution under the influence of an electric field. Ion mobility spectrometry is gas-phase electrophoresis, which separates ions according to their size-to-charge ratio. Unlike mass spectrometry, ion mobility spectrometry is capable of separating isomers. 

A special experimental arrangement of double-focusing sector field mass spectrometry - the Mattauch-Herzog type mass spectrometer has double-focusing properties for ions of all masses... 

Helfrich, A. and Bettmer, J. Determination of phytic acid and its degradation products by ion-pair chromatography (IRC) coupled to inductively coupled plasma-sector field-mass spectrometry (ICR-SE-MS). J. Anal. Atom. Spectrom. 2004, 19, 1330-1334. 

The development by Muller (393) of the field ion microscope gave a considerable thrust to studying surface structures. In a recent modification of this technique, Panitz (394) designed a field desorption spectrometer that promises determination of the crystallographic distribution of species on metal surfaces. Secondary ion mass spectroscopy can also provide some quantitative information of surface species by sputtering atoms with an inert gas ion beam and detecting them by mass spectrometry. Submonolayers of adsorbed gases can be studied by this method (395). 

The three-dimensional quadupole field ion trap - or Paul trap is a three-electrode device [see Figure 4.5(b)]. Ions are injected into the device and collected in packets from an ESI or MALDI source. The ion trap analyzer is capable of MS, MS" (MS = MS-MS-MS) and high-resolution scans (R = 20,000). The ion packets enter through an entrance-end cap and are analyzed by scanning the RF amplitude of the ring electrode. The ions are resonated sequentially from low to high m/z and are ejected from the ion trap through the exit-end cap electrode to a detector. Unlike the triple quadrupole (QqQ) mass spectrometer discussed previously, the ion trap performs tandem mass spectrometry (MS-MS) scan modes in the same analyzer. 

IPM can be used simultaneously with RBS (Rutherford backscattering spectrometry), NRA (nuclear reaction analysis), PIXE (particle induced X-ray emission) or PIGE (particle induced gamma ray emission). More specialized examples include the field ion microscope (FIM), which gives better then atomic resolution in the study of high melting point materials. 

Wdks, A., A Consideration of Ion Chemistry Encountered on the Microsecond Separation Timescales of Ultra-High Field Ion Mobility Spectrometry, 20th annual conference. International Society for Ion Mobility Spectrometry, Edinburgh, Scotland, July 23-28, 2011. 

Prokai, L., Field Desorption Mass Spectrometry, Marcel Dekker, New York, 1990. Mueller, E. W. and Tsong, T. T., Field Ion Microscope, Elsevier, New York, 1969. Inghram, M. G. and Gomer, R., Mass spectrometric analysis of ions from the field microscope, /. Chem. Phys., 22, 1279, 1954. 

In the absence of field, ions fly by inertia with conserved v. These two facts are exploited in time-of-flight mass spectrometry (TOF MS), where ions are accelerated in a pusher region to different v depending on y m/z and fly through a field-free space of well-defined length to the detector. " The measured flight time through that space reveals v and thus m/z of ions present. 

Viehland, L.A., et al. (2000) Comparison of high-field ion mobility obtained from drift tubes and a FAIMS apparatus. International Journal of Mass Spectrometry, 397, 123-130. 

An even more powerful way to cope with spectral overlap is the use of an ICPMS instrument equipped with a double-focusing sector field mass spectrometer (inductively coupled plasma sector field mass spectrometry, ICP-SF-MS) instead of a quadrupole filter. By operating such a mass analyzer at higher mass resolution, the signal of analyte and interfering ions can be resolved in the majority of cases [33,34]. 

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