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1.
The ability to focus the laser accurately onto the sample with a small beam diameter (2.0–3.0 μm) enables laser mass spectrometry to be used as a microprobe. Results from a fully automated ion-mapping system for laser mass spectrometry are described. These results show that the spatial resolution of the laser microprobe is primarily limited by the diameter of the laser beam. Factors such as laser power density, laser focus, sample preparation, and chemical environment influence the reproducibility of laser mass spectra significantly. Calibration curves obtained in the analysis of mixtures of phenanthrolines demonstrate that laser mass spectrometry can be used to quantify organic components. Preliminary results on the detection of neutral molecules resulting from metastable decomposition in the flight tube are also presented.  相似文献   

2.
Both the techniques mentioned provide molecular weight and structural information, but laser microprobe mass spectrometry (LMMS) also provides greater control over the degree of fragmentation and enhanced sensitivity. In addition, LMMS allows microprobe analysis (i.e., spatial resolution of a few μm2) as well as providing quantitative measurements. The less energetic nature of fast-atom-bombardment mass spectrometry (FAB-MS) makes it more suitable for the analysis of highly labile polar compounds and high-mass biopolymers.  相似文献   

3.
This paper presents a set of data which compares the potential and limitations of laser microprobe mass spectrometry (TOF-LMMS and FT-LMMS) and static secondary ion mass spectrometry (S-SIMS) for inorganic speciation at a microscopical level. In general LMMS yields prominent signals of adduct ions consisting of the intact molecule combined with a stable ion, which allows a direct identification of the analyte. S-SIMS also yields abundant diagnostic signals to specify the molecular composition. However, adduct ions are not always present, which means that the identification often relies on fingerprinting. Results further indicate that the potential and the application area of S-SIMS and FT-LMMS are complementary to one another.  相似文献   

4.
Laser microprobe mass spectrometry (LMMS) was applied to coal fly-ash particles prefractionated to homogeneous composition with respect to particle size and density. For major elements, semiquantitative results (<50% relative standard deviation) were obtained; and the characteristic density dependence found for Si, K, Ca and Fe was in good agreement with that obtained by scanning electron microscopy/energy-dispersive x-ray analysis (EDX). The relative sensitivity coefficients, based on concentrations evaluated from the EDX data, coincided with those obtained for the NBS glass particle standard in previous work.  相似文献   

5.
The application of the laser microprobe mass spectrometry to the in-situ characterization of organic aromatic constituents in cryosections of microlichens is described. The samples were photographed before and after microprobe measurement by fluorescence microscopy or transmission electron microscopy to obtain more detailed information on the histological distribution of the compounds examined within the biological structures. This new technology has major advantages for integrated study of the morphology, anatomy and chemistry of plants.  相似文献   

6.
Laser microprobe mass spectrometry (LMMS) is a technique for local analysis of inorganic and organic constituents in the m range. This paper will focus on selected applications. First of all, element detection is illustrated by data from a 50-nm TiW layer on silicon and by the detection of residual Cr on HPLC column packing material. Speciation capabilities of LMMS are demonstrated on pure substances and on a coated neo-ceramic. Finally, the feasibility of organic analysis is shown in the case of a biologically active compound and dyed cloth fibres.  相似文献   

7.
An extended series of positive ions occurring at regular intervals of 24 D is observed in the laser-induced ionization mass spectra of several solid carbonaceous materials. These ions occur with masses up to 3000 D, and can exceed the mass of the parent compound. This effect was found with some polynuclear aromatic hydrocarbons, coal and soots.  相似文献   

8.
Summary Laser microprobe mass analysis (LAMMA) was applied to characterize aerosol particles collected and separated from 16m to 0.06m by a low pressure cascade impactor. Positive ion LAMMA spectra showed characteristic molecular peaks such as PbCl+, a series of Si2O+–Si2O4 + and NaAl2Si2O2 +–NaAl2Si2O5 +, and TiO+ in 0.06–0.12m, 0.5–1m and 4–8m fraction, respectively. In the negative ion LAMMA spectra, it was observed that the fragment peaks of sulfate ions were deficient above 2m and those of nitrate ions were deficient under 2m. LAMMA allows remarkable insights into the chemical nature of aerosol particles.
Charakterisierung luftgetragener Teilchen durch Laser-Microprobe-Massenspektrometrie
Zusammenfassung Laser-Microprobe-Spektrometrie (LAMMS) wurde zur Analyse atmosphärischen Aerosols herangezogen, welches im Korngrößenbereich zwischen 16m und 0.06m mit einem Niederdruckkaskadenimpaktor fraktioniert gesammelt wurde. Positive LAMMS-Spektren zeigten charakteristische molekulare Peaks, wie etwa PbCl+, eine Serie von Si2O+–Si2O4 + und NaAl2Si2O2 +–NaAl2Si2O5 +, sowie TiO+ in der 0,06–0,12-m,- 0,5–1–m- bzw. 4–8-m-Fraktion. In den negativen LAMMS-Spektren konnten über 2m keine Fragmentpeaks für Sulfationen, unter 2m. keine für Nitrationen beobachtet werden. LAMMS ermöglicht eine bemerkenswerte Einsicht in die chemische Natur von Aerosolteilchen.
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9.
Laser microprobe mass spectrometry provides a means of characterizing intermediates and reaction products of the Wittig reaction. The study of mono- and bisphosphonium halides and oligomers of xylene yields more insight in the mass spectrometric behaviour of these molecules under laser-microprobe ionization conditions.  相似文献   

10.
11.
Laser microprobe mass spectrometry is used to identify intrarenal microliths; they appear to consist of either oxalate, urate or phosphate. Crystalline and amorphous deposits in rat and human kidney are pin-pointed by the laser beam and their chemical composition determined by mass spectrometry. The method has the potential for wide application in the identification of single organic, inorganic or combination crystals in histological sections.  相似文献   

12.
Applications of the laser microprobe mass analyzer for characterizing the surface of chemically modified minerals (crown ether/montmorillonite and organosilane/sepiolite) and for detecting micro-crystallites at the surface of an inorganic matrix (brucite surface layer of chrysotile fibers) were investigated using laser desorption conditions. The laser microprobe is shown to be a versatile tool for these applications.  相似文献   

13.
This study attempted to determine the molecular composition of inorganic analytes at the surface of solids by Fourier transform laser microprobe mass spectrometry (FT LMMS) with an external ion source. A database was established from the analysis of pure compounds. FT LMMS uses a similar ionization as the older LMMS instruments with time-of-flight (TOF) mass analyzer. However, apart from the mass resolution, the mass spectral patterns can be significantly different in FT LMMS compared to TOF LMMS. FT LMMS yields detailed information on the analyte by means of structural fragments, enabling us to specify the main building blocks, as well as adduct ions, consisting of the analyte molecule and a stable ion. Hence, deductive reasoning allows tentative characterization of the analogs without reference spectra, except for compounds with the same elements in different stoichiometries. In that case comparative data are needed.  相似文献   

14.
Journal of Radioanalytical and Nuclear Chemistry - The 6th Collaborative Materials Exercise, CMX-6, was organized by the Nuclear Forensic International Technical Working Group in 2018 and 2019. Two...  相似文献   

15.
The applicability of laser ablation (LA) inductively coupled plasma (ICP) spectrometry for assessing elemental distributions in layered ceramics was investigated and compared with electron probe microanalysis (EPMA). Ordinary glazed wall tiles were employed as model specimens due to their defined structure and composition. They were used for calibration in the analysis of ancient pottery. A qualitative depth profile was acquired by single-spot laser drilling perpendicular to coatings with a Nd:YAG (1064 nm) laser coupled with an ICP optical emission spectrometer (OES). The lower lateral resolution associated with the laser spot diameter of 1.0 mm led to smoothing of the depth profile due to the averaging of local irregularities. In addition, transverse line scans by ablation across the tile section using an ArF* (193 nm) laser coupled with an ICP mass spectrometer (MS) were performed. LA-ICP-OES depth profiles and LA-ICP-MS transverse scans were validated by EPMA section scans and 2D back-scattered electrons images. The LA-ICP-OES acquisition was less dependent on sample surface and layer irregularities, whereas the transverse line scan over the tile section with the small-spot beam offered insight into the micromorphology of the individual layer. The combined approach revealed the occurrence of individual mineral grains, micro-heterogeneities and the character of interfaces between layers.  相似文献   

16.
Single crystal silicon samples of various boron concentrations are studied using an ion microprobe. Argon and oxygen ion beams are used for the scanning and the determination of the boron profiles. Erosion rates are discussed.  相似文献   

17.
Summary Mass spectrometry of nonvolatile substances by laser-induced-ionization with the laser microprobe mass analyzer (LAMMA®1000), is applied to analytical chromatographic techniques by means of the electrospray technique. As typically resulting from chromatographic analysis, substance amount in the picogram range (preparation included) and concentration of the substance in the range of 10–6 to 10–8 mole·l–1 is sufficient for mass spectroscopic determination. However, the amount of substance needed to produce each mass spectrum is found to be in the femtogram range.In this certain regime of mass and concentration, the contaminants in the solvent act as marker for the site of trace-investigation, i. e. indicate those sites where the substance is sufficiently available to produce substance specific mass spectra.
Bestimmung von Femtogramm organischer und anorganischer Verbindungen mittels LAMMA
Zusammenfassung Die Massenspektrometrie nicht-flüchtiger Substanzen durch Laser-induzierte Ionisation mit dem LAMMA®-1000 wurde mit Hilfe der Elektrospray-technik auf analytisch-chromatographische Verfahren angewendet. Bei der chromatographischen Analyse fallen Substanzmengen im Picogrammbereich in Konzentrationen von 10–6–10–8 Mol/l an, die für die massenspektroskopische Bestimmung hinreichend sind. Die für jedes Massenspektrum erforderliche Substanzmenge liegt hingegen im Femtogrammbereich. Bei solchen Massen bzw. Konzentrationen dienen die Verunreinigungen des Lösungsmittels als markierende Träger für die Spurenuntersuchung, d. h. sie weisen auf jene Stellen, an denen die Substanzmenge hinreicht, um spezifische Massenspektren zu erhalten.
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18.
Ammonia is important in the atmosphere because it neutralizes acidic species. The relative importance of different inorganic ammonium compounds (chloride, nitrate and sulfate) in marine air chemistry was studied by single-particle characterization with the laser microprobe mass analyser. Standard aerosols were generated as a reference for compound identification, based on the fingerprint spectra obtained, and calculation of the relative sensitivity achieved for different ions in a marine aerosol matrix. The relative sensitivity for ammonium was low. Aerosol samples were collected in the Southern Bight of the North Sea under different meteorological conditions and examined for their ammonium compounds. Samples collected during an inversion period with continental influences showed a much higher content in all particles than samples collected under different meteorological conditions, where ammonium was mostly detected in the submicrometer particle-size range.  相似文献   

19.
The use of laser microprobe mass spectrometry (LMMS) for the structural characterization of thermolabile quaternary phosphonium salts has been evaluated. A comparison has been made between LM mass spectra obtained by direct analysis of “neat” organic salts and the corresponding “matrix-assisted” LM mass spectra. Main limitations of LMMS for the direct analysis of neat organic salts (i.e., no matrix) result from (1) formation of artifact ions that originate from thermal degradation and surface recombination reactions and (2) poor shot-to-shot reproducibility of the spectra. Dilution of the organic salts in a suitable, UV-absorbing matrix (e.g., nicotinic acid) significantly enhances the quality of the LM mass spectra. Improvements are: (1) an increase of the ion yield of preformed cations, (2) reduction or elimination of thermal decomposition and other deleterious surface reactions, and (3) a much better shot-to-shot spectral reproducibility. An interesting analytical feature is that these LM mass spectra, which contain only a few matrix peaks, can be obtained for subnanogram amounts of sample. The results also show that triphenylphosphonium salts with polycyclic aromatic substituents can be used as “molecular thermometers” to probe both the temperatures experienced by the sample molecules during the laser-induced desorption ionization process and the internal energies of the desorbed ion species. In this way, quaternary phosphonium salts can be used for evaluating whether improvements have been achieved by applying different sample treatments. Comparison of four different matrices (i.e., nicotinic acid, ammonium chloride, glycerol, and 3-nitrobenzylalcohol) indicates that the effectiveness of a matrix to reduce thermal degradation and to decrease the internal energies of the ions depends on the UV-absorption characteristics and the volatilization/sublimation temperature of the matrix material.  相似文献   

20.
Microprobe two-step laser desorption/laser ionization mass spectrometry (μL2MS) and gas chromatography/mass spectrometry (GC/MS) were used to analyze polycyclic aromatic hydrocarbons (PAHs) in ancient terrestrial rocks. μL2MS provides an in situ analysis of very small samples, records the PAHs with no isomer information, and gives quantitative data on the degree of alkylation of a given PAH series over the complete mass range. GC/MS provides isomer separation and quantitation of PAHs in bitumen but not kerogen, and is limited by sample size. Combination of these techniques allows analysis of very small samples by μL2MS with GC/MS confirmation of isomer distributions of the solvent extractable components (bitumen). It was found that the concentration of bitumen within the rock samples affects the PAH alkylation signal for μL2MS. At low bitumen concentrations μL2MS can produce pyrolysis products from kerogen that is present; however, as bitumen concentrations increase, the PAH distribution from bitumen dominates the signal.  相似文献   

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