Laser microprobe mass analysis (LAMMA) of pyridine adsorbed on some clay minerals from Turkey

Using laser microproble mass analysis (LAMMA), it is possible to characterize the inorganic composition of clays and to study adsorption phenomena. Natural sepiolite, (Na-sepiolite), montmorillonite and saponite samples from Anatolia (Turkey) have been investigated. All the clays gave different fingerprint mass spectra which allowed a quick estimation of the relative amounts of exchangeable cations as well as the trace contaminants and the homogeneity of their distribution. The adsorption behaviour of these clays for pyridine was also studied and it appeared that pyridine molecules penetrated the inner layers, as well as being adsorbed on the external surface.     

Computer aided mathematical analysis of interferences in spark source mass spectrometry spectra

Summary When analysing sulphide ores by spark source mass spectrometry different interferences on some mass-to-charge ratios, such as 60–62 (Ni) and 193–197 (Ir,Pt,Au), have been observed. These lines should be used in the estimation of element concentrations. Our program (SM13) gives hints to possible molecular ions derived from the matrix of the sample by using the theory of combination.The validity of this theory was checked by analysing the ASK III standard [3] and mixtures of sulphides and oxides. The formation of interfering molecular ions such as SiS⁺ and AgFeS⁺ was checked.

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Computergestützte mathematische Auswertung von Interferenzen in Funken-Massenspektren

Zusammenfassung Bei der Analyse sulfidischer Erze wurden in der Funken-Massenspektrometrie für die Masse-zu-Ladungs-Verhältnisse 60–62 (Ni) sowie 193–197 (Ir,Pt,Au), die für die Elementbestimmungen verwendet werden sollten, Interferenzen beobachtet. Hierzu wurden mit Hilfe eines Auswertungsprogramms (SM13) durch mathematische Kombinatorik Hinweise auf Interferenzen durch mögliche Molekülionen aus der Matrixzusammensetzung abgeleitet.Die Anwendbarkeit des mathematischen Modells wurde am ASK III Standard [3] sowie an Mischungen von Sulfiden und Oxiden erprobt. Die Bildung der interferierenden Molekülionen des Typs SiS⁺ und AgFeS⁺ konnte nachgewiesen werden.

     

Evaluation of mass spectral library search algorithms implemented in commercial software

Performance of several library search algorithms (against EI mass spectral databases) implemented in commercial software products ( acd/specdb , chemstation , gc/ms solution and ms search ) was estimated. Test set contained 1000 mass spectra, which were randomly selected from NIST'08 (RepLib) mass spectral database. It was shown that composite (also known as identity) algorithm implemented in ms search (NIST) software gives statistically the best results: the correct compound occupied the first position in the list of possible candidates in 81% of cases; the correct compound was within the list of top ten candidates in 98% of cases. It was found that use of presearch option can lead to rejection of the correct answer from the list of possible candidates (therefore presearch option should not be used, if possible). Overall performance of library search algorithms was estimated using receiver operating characteristic curves. Copyright © 2015 John Wiley & Sons, Ltd.     

Laser microprobe mass spectrometry (LMMS) of intracrystalline crown ether and cryptand complexes in layer silicates

Laser microprobe mass spectrometry (LMMS) allows the characterisation of organic inclusions in mineral materials. The complexes are detected as cationized or protonated molecules, arising from the intact desorption or from recombination within the laser generated microplasma. The results obtained sustain the interpretation from other techniques concerning the nature of the cation-ligand association and the proton exchange of the cryptand for acidic Cu²⁺-ions.     

Applications of laser microprobe mass spectrometry in organic analysis

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.     

Characterization of airborne particulates by laser microprobe mass analysis

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.

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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.

     

Characterization of coal fly-ash particles by laser microprobe mass spectrometry

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.     

Observations of trends for singular values and eigenvectors from library searching ultraviolet-visible spectra with spectral subtraction

A promising procedure for computerized library searching and identification of ultraviolet-visible spectra for one- and two-component mixtures is evaluated. The procedure is based on singular value decomposition and utilizes band position and shape. Searching more than one library spectrum at a time is possible. Library spectra which have similar spectra (collinear) with the sample and each other are indicated by two measures. First, a large condition index must be obtained, and second, two or more large variance-decomposition proportions in the same row need to be associated with the large condition index. The searching procedure has a significant degree of differentiation between the actual sample and potential candidates and is compared with the dot product, Euclidean distance and the correlation coefficient.     

Comparison of laser microprobe mass spectrometry and fast-atom-bombardment mass spectrometry for organic analysis

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.     

Computer processing and interpretation of mass spectral information. Part IX—generalized characteristics of mass spectra

The formation of numerical generalized characteristics (indices) of mass spectra by using one or two experimental parameters (mass numbers and/or ion peak amplitudes) is suggested. The influence of the measuring error of peak amplitudes on the statistical characteristics of indices was studied. It was ascertained by four classes of organometallic compounds that within an isolated class the value of each index is distributed by a normal law. The possibility of using mass spectral indices for the identification of unknown compounds is demonstrated.     

Investigation of semi-thin cryosections of lichens by laser microprobe mass spectrometry

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.     

Nuclear methods of analysis applied to quantitation in laser microprobe mass spectrometry

Laser microprobe mass spectrometry (LMMS) detection limits for mercury have been determined using mercury-doped Spurr's tissue embedding medium. Actual mercury concentrations were confirmed via INAA. Procedures have also been developed to measure lithium and indium concentrations in thin films of polymerized Spurr's samples via PIGE and PIXE. These elements are currently being investigated as laser power density internal standards in the analysis of human tissue for studies of trace element involvement in neurological diseases.     

The use of laser microprobe mass spectrometry for monitoring the Wittig synthesis

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.     

Surface characterization of pure and chemically modified minerals by laser microprobe mass spectrometry

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.     

Fourier transform laser microprobe mass spectrometry for the molecular identification of inorganic compounds

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.     

Quantitative investigation of Cu-Ni and Ag-Pd alloys with a laser microprobe mass analyzer

Summary Quantitative Investigation of Cu-Ni and Ag-Pd Alloys with a Laser Microprobe Mass Analyzer The analytical capability of the LAMMA-1000 instrument is discussed with respect to the evaporation and ionization probability for known concentrations of binary alloys with gradually changing composition. The relative sensitivity coefficients of Ni to Cu and Pd to Ag were found to be constant at 0.95±0.20 and 0.54±0.09, respectively, for a variety of binary alloy. No correlation with the alloy density was found for a variety of binary alloys. The ionization probability remains constant when the alloy composition changes. It is assumed that the selective evaporation does not occur within and near the laser focus. The phase transition and evaporation kinetics with respect to time and space seem to be a less dominant factor for ion formation in the LAMMA instrument. The absolute quantitative analysis is possible by the use of a calibration curve, if the total ions or the sampling volume can be determined. The use of the relative sensitivity coefficients is an effective method for a quantitative analysis with an error of 10–30%.     

Laser microprobe mass spectrometry of quaternary phosphonium salts: Direct versus matrix-assisted laser desorption

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.     

Identification of inorganic and organic microliths in kidney sections by laser microprobe mass spectrometry

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.     

Semi-automated data processing of hydrogen exchange mass spectra using HX-Express

A Microsoft Excel utility, HX-Express, that significantly accelerates the analysis of hydrogen exchange mass spectrometry data is described. HX-Express generates deuterium uptake and peak width plots from peaks in mass spectral data. Data analysis is intentionally semi-automated, requiring that the user find the peaks to be analyzed. The peaks are entered in the form of x, y lists of m/z versus intensity or can be directly imported from Waters MassLynx software. Analysis of data with HX-Express provides the same results as manual data processing but is substantially faster. In addition to speed, HX-Express provides and preserves visual and numeric displays of the analysis process for quality control.     

Assessment of local analysis by fourier transform laser microprobe mass spectrometry with external ion source

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.