Field ionization mass spectrometry samples

Seven Argonne Premium coal samples ranging from lignite to low volatile bituminous in rank were analyzed by Pyrolysis-Field Ionization Mass Spectrometry (Py-FIMS) in order to determine the existence and structural nature of a thermally extractable "mobile phase". In addition, Curie-point Pyrolysis-Low Voltage Mass Spectrometry (Py-LVMS) was employed to demonstrate the importance of mild oxidation on the thermally extractable mobile phase components. 

Analytical pyrolysis is defined as the characterization of a material or a chemical process by the instrumental analysis of its pyrolysis products (Ericsson and Lattimer, 1989). The most important analytical pyrolysis methods widely applied to environmental samples are Curie-point (flash) pyrolysis combined with electron impact (El) ionization gas chromatography/mass spectrometry (Cp Py-GC/MS) and pyrolysis-field ionization mass spectrometry (Py-FIMS). In contrast to the fragmenting El ionization, soft ionization methods, such as field ionization (FI) and field desorption (FD) each in combination with MS, result in the formation of molecule ions either without, or with only very low, fragmentation (Lehmann and Schulten, 1976 Schulten, 1987 Schulten and Leinweber, 1996 Schulten et al., 1998). The molecule ions are potentially similar to the original sample, which makes these methods particularly suitable to the investigation of complex environmental samples of unknown composition. 

Mass Spectrometry. Electron impact (El) mass spectrometry was done at NRL on the effluent from a 6 ft. OV-101 packed GC column programmed from 70 to 210°C. Field ionization mass spectrometry (FIMS) was performed by SRI International on contract to NRL. In this latter analysis, the fuel sample was frozen on a solids inlet probe prior to insertion into the mass spectrometer. The spectra accumulated for each mass during a temperature program were normally totaled for data presentation (6). Molecules boiling below 140°C are lost or depleted with this technique but such compounds comprise a very small fraction of JP-5 or DFM. Since the ionization efficiency for hydrocarbon classes is currently under study, the FIMS data are utilized primarily in a qualitative sense. 

When placed in a strong electrostatic field (10 —10 V cm ) a molecule can lose an electron and form a positive charged ion. In the earlier technique of field ionization mass spectrometry the sample was first vaporized prior to... 

These methods require that the sample is either a gas or, at least, a volatile substance which can be easily converted into a gas (this explains the utility of mass spectrometry in the field of organic chemistry). In inorganic chemistry it is often more difficult to obtain a gaseous sample, and so other ionization sources have been developed. If the sample is thermally stable, it may be volatilized by depositing it on a filament and heating the filament (thermal ionization mass spectrometry - see below). In restricted cases (e.g., organometallic chemistry), chemical treatment of the sample may give a more volatile sample. 

The development of matrix-assisted laser desorption ionization (MAEDI) has advanced the entire field of mass spectrometry. To use this ionization method, the sample is mixed into a matrix that absorbs the laser wavelength extremely well (approximately 10,000 1 matrix analyte) and the mixture is placed on a solid substrate. Absorption of the laser causes the matrix to explode, ejecting the intact, nonvolatile molecules of interest into the gas phase. Proton exchange or alkali metal attachment occurs in the gas plume and the ionized species can be detected. 

Schaub,T. M., Linden, H. B., Hendrickson, C. L., and Marshall, A. G. (2004). Continuous flow sample introduction for field desorption/ionization mass spectrometry. Rapid Commun. Mass Spectrom. 18,1641-1644. 

Analytical methods for tocol analysis have continued to improve, as noted by Abidi (2000), and in the intervening ten years, as noted in this chapter. We predict that advances will continue to be made in the field of the chromatographic analysis of tocols. Also, we believe that lipidomic methods (quantitative analysis via direct injection tandem electrospray ionization mass spectrometry) will be developed for the rapid analysis of tocols, just as these methods have already been used for the profiling of phospholipids and glycolipids (Han, 2011 Welti, 2011). These methods usually involve the direct injection of lipid samples into a... 

At the outset of the structure investigation it was hoped that single-crystal X-ray methods might be successful, particularly with the large alkaloids however, as a number of trials were not promising, the approaches to structures have relied on spectroscopic and chemical methods. Spectroscopic examination involved electron impact, chemical ionization, and field desorption mass spectrometry, H- and C-nuclear magnetic resonance study (sometimes NOE and correlation spectroscopy), and this was followed by isolation of the polyhydroxylated core by alcoholysis or hydrolysis. Core 30 was novel and its structure established spectroscopically 48), whereas euonyminol was characterized as its octaacetate and compared with an authentic sample. 

In atomic laser spectroscopy, the laser radiation, which is tuned to a strong dipole transition of the atoms under investigation, penetrates the volume of species evaporated from the sample. The presence of analyte atoms can be measmed by means of the specific interaction between atoms and laser photons, such as by absorption techniques (laser atomic absorption spectrometry, LAAS), by fluorescence detection (laser-induced fluorescence spectroscopy, LIFS), or by means of ionization products (electrons or ions) of the selectively excited analyte atoms after an appropriate ionization process (Figures lA and IB). Ionization can be achieved in different ways (1) by interaction with an additional photon of the exciting laser or of a second laser (resonance ionization spectroscopy, RIS, or resonance ionization mass spectrometry, RIMS, respectively, if combined with a mass detection system) (2) by an electric field applied to the atomization volume (field-ionization laser spectroscopy, FILS) or (3) by collisional ionization by surrounding atoms (laser-enhanced ionization spectroscopy, LEIS). 

The main purpose of the detector in a field-flow fractionation (FFF) system is to quantitatively determine particle number, volume, or mass concentrations in the FFF size-sorted fractions. Consequently, a number, volume, or mass dependent size distribution of the sample can be derived from detection systems applied to FFF [e.g., (UV-Vis) fluorescence, refractive index, inductively coupled plasma ionization mass spectrometry (ICPMS)]. Further, on-line light scattering detectors can provide additional size and molecular weight distributions of the sample. 

The basic principles of thermal ionization mass spectrometry (TIMS) operation were described in Chapter 1 a drop of the liquid sample is deposited on a filament, a low electric current heats the filament, and the solution is evaporated to dryness. The filament current (temperature) is then raised and atoms of the sample are emitted and ionized (either by the same filament or by a second electron emitting filament). The ions are accelerated by an electric field, pass through an electrostatic analyzer (ESA) that focuses the ion beam before it enters a magnetic field that deflects the ions into a curved pathway (in some devices, the ions enter the magnetic field before the ESA—referred to as reverse geometry). Heavy and light ions are deflected by the field at different curvatures that depend on their mass-to-charge ratio. A detector at the end of the ion path measures the ion current (or counts the ion pulses). There are many variations of ion sources, ion separation devices, and detectors that are used in TIMS instruments and specifically adapted for ultratrace or particle analysis. 

Wey AB, Thormann W (2001) Head-column field-amplified sample stacking in presence of siphoning Application to capillary electrophoresis-electrospray ionization mass spectrometry of opioids in urine. J Chromatogr A 924(l-2) 507-518... 

Owing to its compatibility with solution samples, ESI is preferred over other ionization methods in many MS fields. Applications of metal ion adducts have been reported for ESI [55-57]. For example, ESI can be used to produce alkali-metal adducts of antibiotics that do not form abundant [M+H]+ ions. Informative adducts between alkali-metal ions and peptides have been observed under a variety of conditions of electrospray ionization mass spectrometry (ESI-MS). It should be noted, however, that the presence of salt ion adducts cause the signal suppression and interference with the interpretation of the mass spectra, particularly in analytical MS of proteins and other biological molecules. 

Recent developments for generating gas-phase samples from involatile chemicals have increased applications for those structural techniques that require samples to be presented in gaseous form. Techniques for generating gaseous molecular ions from the condensed phase have had massive impacts in the fields of mass spectrometry and photoelectron spectroscopy. We discuss a number of different ionization techniques in Section 11.2.1, but for now comment on the particular success of electrospray... 

Soltmann B, Sweeley C C, Holland J F 1977 Electron impact ionization mass spectrometry using field desorption activated emitters as solid sample probes. Anal Chem 49 1164-1166... 

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