Probes mass spectrometry

In order to relate material properties with plasma properties, several plasma diagnostic techniques are used. The main techniques for the characterization of silane-hydrogen deposition plasmas are optical spectroscopy, electrostatic probes, mass spectrometry, and ellipsometry [117, 286]. Optical emission spectroscopy (OES) is a noninvasive technique and has been developed for identification of Si, SiH, Si+, and species in the plasma. Active spectroscopy, such as laser induced fluorescence (LIF), also allows for the detection of radicals in the plasma. Mass spectrometry enables the study of ion and radical chemistry in the discharge, either ex situ or in situ. The Langmuir probe technique is simple and very suitable for measuring plasma characteristics in nonreactive plasmas. In case of silane plasma it can be used, but it is difficult. Ellipsometry is used to follow the deposition process in situ. 

Thermal-programmed solid insertion probe mass spectrometry (TP-SIP-MS) has been proposed [247,248], in which the solid insertion probe consisting of a water-cooled microfumace enters the mass spectrometer via an airlock. The sample is contained in a small Pyrex tube (i.d. 1 mm, length 20 mm). The TIC trace gives a characteristic evolved gas profile for each compound in a mixture of materials, and the mass spectra associated with each TIC peak give a positive identification of that component as it is vaporised. TP-SIP-MS is appropriate for analysis of small solid particles which are volatile, or produce volatile decomposition products. The technique is a form of evolved gas analysis. 

Direct probe mass spectrometry. Glycosphingolipids (30-100 pg) were permethylated as described (12). The samples (less than 5 p g) were subjected to electron impact/desorption analysis with a Varian MAT CH-5 DF mass spectrometer under the following conditions emission current, 300pA electron energy, 70 eV acceleration voltage, 3KV ion source temperature, 160° C emitter wire current, programed from 0 to 35mA. 

This information was obtained from samples of less than 5 pg by electron impact/desorption direct probe mass spectrometry. On the basis of complete structural analyles, to be presented elsewhere, we have been able to determine that the four fractions isolated thus far actually contain six different glycosphingolipids with the following structures ... 

Frequently industrial hygiene analyses require the identification of unknown sample components. One of the most widely employed methods for this purpose is coupled gas chromatography/ mass spectrometry (GC/MS). With respect to interface with mass spectrometry, HPLC presently suffers a disadvantage in comparison to GC because instrumentation for routine application of HPLC/MS techniques is not available in many analytical chemistry laboratories (3). It is, however, anticipated that HPLC/MS systems will be more readily available in the future ( 5, 6, 1, 8). HPLC will then become an even more powerful analytical tool for use in occupational health chemistry. It is also important to note that conventional HPLC is presently adaptable to effective compound identification procedures other than direct mass spectrometry interface. These include relatively simple procedures for the recovery of sample components from column eluate as well as stop-flow techniques. Following recovery, a separated sample component may be subjected to, for example, direct probe mass spectrometry infra-red (IR), ultraviolet (UV), and visible spectrophotometry and fluorescence spectroscopy. The stopped flow technique may be used to obtain a fluorescence or a UV absorbance spectrum of a particular component as it elutes from the column. Such spectra can frequently be used to determine specific properties of the component for assistance in compound identification (9). 

The use of preparative TLC is, moreover, a way of obtaining sufficiently large amounts of degradation products for the structure elucidation direct probe mass spectrometry or nuclear magnetic resonance spectrometry. 

Direct insertion probe mass spectrometry (DIP-MAS) analyses of poly(methyl methacrylate) (PMMA), poly(vinyl acetate) (PVAc), and their coalesced and precipitated blends were performed [51] (see Fig. 21). The fact that the pyrolysis mass... 

Herod AA, Kandiyoti R. 1995. Fractionation by planar chromatography of a coal tar pitch for characterization by size exclusion chromatography, UV fluorescence and direct probe mass spectrometry. J Chromatogr 708 143-160. 

Fig. 9. Distribution of iron in a cell of an uterus gland determined by laser probe mass spectrometry , a Mass spectra of various sample spots diminished by the background spectrum, b Abundance profile of iron along the gland cell...

Trimpin, S., Wijerathne, K., and McEwen, C.N. (2009) Rapid methods of polymer and polymer additives identification Multi-sample solvent-free MALDl, pyrolysis at atmospheric pressure, and atmospheric solids analysis probe mass spectrometry. Anal. Chim. Acta, 654, 20-25. 

One of the first reports of a forensic analysis of TATP in the United States came following an accidental detonation of a homemade TATP explosives device [41]. The TATP was analyzed by direct insertion probe-mass spectrometry (DIP-MS) with El, as well as methane and... 

Two papers describe in detail methods used to transfer material separated by TLC into sample holders suitable for direct insertion probe mass spectrometry. Rix et al. (26) transfer the scraped sample spot into a drawn-out elution column, and then elute the sample through a plug into a separate part of the column (Figure 2). The concentrated sample solution is then evaporated onto the tip of a standard direct insertion probe. Kohler (27) describes a similar method that can also be used for the collection of samples for a subsequent GC/MS analysis. 

Figure 19 Mass spectrum of 25-OH-D3 purified from Hep 3B cells (upper panel) compared to the mass spectrum of synthetic 25-OH-D3 (lower panel). Hep 3B cells were incubated with vitamin D3 (50 pM) for 48 h. Flasks were then extracted and the lipid extract dried under nitrogen and purified on HPLC (conditions Zorbax SIL [6.2 mm X 25 cm], solvent HIM 96/3/3, flow rate 2 mL/min). A metabolite peak possessing the vitamin D chromophore and comigrating with synthetic 25-OH-D3 was collected, purified further on a different HPLC system (conditions Zorbax CN [4.6 mm X 25 cm], solvent HIM 94/ 5/1, flow rate 1 mL/min), and then dried under nitrogen and subjected to direct probe mass spectrometry using electron impact EI(+) ionization. The putative 25-OH-D3 gave the expected molecular ion with m/z 400 the other ions observed were consistent with the molecule being 25-hydroxylated (see inset fragmentation pattern). (From Ref. 207.)...

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