Characterization of VX on concrete using ion trap secondary ionization mass spectrometry

The nerve agent VX (O-ethyl S-2-diisopropylaminoethyl methyl phosphonothiolate) was analyzed on the surface of concrete samples using an ion trap secondary ion mass spectrometer (IT-SIMS). It was found that VX could be detected down to an absolute quantity of 5 ng on a concrete chip, or to a surface coverage of 0.0004 monolayers on crushed concrete. To achieve these levels of detection, the m/z 268-->128 ion fragmentation was measured using MS2, where m/z 268 corresponds to [VX + H]+, and 128 corresponds to a diisopropylvinylammonium isomer, that is formed by the elimination of the phosphonothiolate moiety. Detection at these levels was accomplished by analyzing samples that had been recently exposed to VX, i.e., within an hour. When the VX-exposed concrete samples were aged, the SIMS signature for intact VX had disappeared, which signaled the degradation of the compound on the concrete surface. The VX signature was replaced by ions which are interpreted in terms of VX degradation products, which appear to be somewhat long lived on the concrete surface. These compounds include ethylmethylphosphonic acid (EMPA), diisopropyl taurine (DIPT), diisopropylaminoethanethiol (DESH), bis(diisopropylaminoethane) disulfide [(DES)2], and a particularly tenacious compound that may correspond to diisopropylvinylamine (DIVA), or an isomer thereof. It was found that the thiolamine-derived degradation products DIPT, DESH, and (DES)2 were removed with isopropyl alcohol extraction. However, the DIVA-related degradation product was observed to strongly adhere to the concrete surface for longer than one week. Although quantitation was not possible in this set of experiments, the results clearly show the rapid degradation of VX on concrete, as well as the surface sensitivity of the IT-SIMS for intact VX and its adsorptive degradation products.     

Depth profile measurement by secondary ion mass spectrometry

The possibilities of measuring depth profiles by secondary ion mass spectrometry are evaluated. The influence of different instrumental and experimental parameters on depth resolution in the profiles are studied: the effects of primary ion beam characteristics, reactive gas adsorption and mechanical aperturing in secondary ion extraction are discussed. Beam effects are studied from the point of view of surface damage. The effects of secondary processes, such as crater edge effects, element mixing, preferential sputtering, background signals, (residual) gas contamination and ion-induced topographical and compositional changes are studied for thin metal and binary materials.     

Protein denaturation detected by time-of-flight secondary ion mass spectrometry

In the present work we investigate the denaturation of a functional protein, horseradish peroxidase (HRP), under various experimental conditions using time-of-flight secondary ion mass spectrometry. HRP was immobilized on TiO(2), and the samples were stored under different conditions. The activity of the enzyme was assessed colorimetrically and compared to ToF-SIMS spectra. We show that denaturation of the protein can be monitored using the ToF-SIMS signal of the disulfide bonds, which is related to the tertiary structure of the protein. As disulfide bonds appear in a vast range of proteins, the present findings may be of wide significance; i.e., a tool is provided that can allow the investigation of the presence of an active protein structure by a comparably simple surface analytical method.     

Surface analysis of polymer materials by secondary ion mass spectrometry

Atomic as well as molecular secondary ions are emitted from the uppermost monolayer of a solid during ion bombardment. Mass analysis of these positive and negative secondary ions supplies detailed information on the chemical composition of the bombarded surface. High mass range (> 10,000 u), high mass resolution (m/Δm > 10,000), accurate mass determination (ppm range) and high sensitivity (ppm of a monolayer) are achieved by applying time-of-flight (TOF) mass analyzers. TOF-SIMS has been successfully applied to a wide variety of polymer materials, including polymer blends, chemically or plasma modified surfaces, and plasma polymerization layers. Detailed information on the composition of repeat units, endgroups, oligomer distributions, additives, as well as surface contaminants can be obtained. Basic concepts of TOF-SIMS will be described and typical analytical examples for the characterization of polymer materials will be presented.     

Quantitative analysis of microstructures by secondary ion mass spectrometry.

The focus of this review is on trace-element quantitation of microstructures in solids. This review is aimed at the nonspecialist who wants to know how secondary ion mass spectrometry (SIMS) quantitation is achieved. Despite 35 years of SIMS research and applications, SIMS quantitation remains a fundamentally empirical enterprise and is based on standards. The most used standards are "bulk standards"-solids with a homogeneous distribution of a trace element-and ion-implanted solids. The SIMS systematics of bulk standards and ion-implanted solids are reviewed.     

Image processing in secondary ion mass spectrometry

The application of image processing in secondary ion mass spectrometry is discussed. The Cameca 4f SIMS uses a single microchannel plate and a highly sensitive camera in combination with an image processor with real time capabilities (Kontron IBAS). An automation procedure with image integration, extended dynamic range image acquisition and retro depth profiling is presented and illustrated with practical applications.     

Quantitative analysis by thin-layer chromatography with secondary ion mass spectrometry

Summary A direct combination of thin-layer chromatography with secondary ion mass spectrometry (TLC/SIMS) provides a method for the quantitative analysis of thermally unstable compounds or compounds of low volatility such as nicergoline. The method is very simple and has excellent precision. The analysis was performed by using an aluminium TLC plate and a mixture of methylene chloride, acetone, and distilled water as a developing solvent. After development the portion of the plate with the nicergoline and the internal standard spots was cut off the TLC plate, and was attached to the SIMS holder directly. The amount of nicergoline was determined from the ratio of the fragment ion intensity of the nicergoline to the internal standard. The calibration curve was linear, and the detection limit was 10 ng at a signal-to-noise ratio of 5. This method should be considered for application to the determination of drugs in biological samples and also for the determination of possible impurities and decomposition products in drugs.     

Characterization of combinatorially designed polyarylates by time-of-flight secondary ion mass spectrometry

A series of 16 polyarylates, with well-controlled and systematically varying chemistry, has been characterized by time-of-flight secondary ion mass spectrometry (TOF-SIMS). The polymers are structurally identical except for the incremental additions of C2H4 units to the backbone and sidechain. From the spectra, peaks characteristic of all polyarylates are identified. Furthermore, evaluation of the spectra and identification of unique signals allow classification of the polyarylates according to sidechain and backbone chemistry.     

Structural analysis of secondary ions by post-source decay in time-of-flight secondary ion mass spectrometry

Tandem mass spectrometry measurements have been achieved using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and a post source decay (PSD)-like method. The performance of the method has been demonstrated on model molecules with well-known fragmentation pathways. Several lipids have been fragmented including the phosphocholine ion, phosphatidylcholines, cholesterol and vitamin E. Pure samples were analyzed, and the results compared with those obtained with the same compounds on a quadrupole-TOF hybrid mass spectrometer. Then, the structures of some lipids which are currently observed in the TOF-SIMS imaging of mammalian tissue sections were verified.     

Alpha spectrometry and secondary ion mass spectrometry of electrodeposited uranium films

Electrodeposited natural uranium films prepared by electrodeposition from solution of uranyl nitrate UO₂(NO₃)₂·6H₂O on stainless steel discs in electrodeposition cell. Solutions of NaHSO₄, and Na₂SO₄ and electric current from 0.50 up to 0.75 A were used in this study. Recalculated weights and surface’s weights of ²³⁸U from the alpha activities and secondary ion mass spectrometry (SIMS) intensities resulted in a linear regression. A dependency between of ²³⁸U surface’s weights recalculated from alpha activities and signal intensity of ²³⁸U in SIMS was investigated in order to determine a potential of SIMS in quantitative analysis of surface samples containing uranium. In the SIMS spectra of electrodeposited uranium films we found that upper layer consist not only from isotopes of uranium (ions ²³⁴U⁺, ²³⁵U⁺, and ²³⁸U⁺). In the positive polarity SIMS spectra, various molecules ions of uranium were suggested as UH⁺, UH₂ ⁺, UO⁺, UOH⁺, UO₂ ⁺, UO₂H⁺, UO₂H₂ ⁺, as well as possibly ions UNO⁺ and UNOH⁺.     

Semiquantitative analyses by secondary ion mass spectrometry using one fitting parameter

Summary A procedure for SIMS semiquantitative analysis, based on the use of one fitting-parameter, has been applied to metal and mineral standards with satisfactory results. Values of this parameter for various matrices are given, and prospects for analyses involving no reference elements are discussed. Analytical accuracies obtainable for individual elements are assessed in terms of matrix-independent error factors.

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Zusammenfassung Eine Methode zur semiquantitativen SIMS-Analyse, die im Gegensatz zu den aus der Literatur bekannten Verfahren nur einen Anpassungsparameter benötigt, wurde mit gutem Erfolg an Metall- und Mineralstandards getestet. Werte des Anpassungsparameters für verschiedene Matrices wurden angegeben und Aussichten für eine Weiterentwicklung dieser Methode in Richtung auf standardfreie Analysen wurden besprochen. Die analytische Richtigkeit für einige Elemente wurde mit Hilfe von matrixunabhängigen Fehlerfaktoren abgeschätzt.

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Presented at the International Symposium on Microchemical Techniques 1977, Davos, May 1977.     

A pulsed time-of-flight mass spectrometer for liquid secondary ion mass spectrometry

The design and performance of a new time-of-flight mass spectrometer is reported. The instrument combines the advantages of a pulsed drawout TOF analyzer with a liquid secondary ion source. Differences from commercially available pulsed TOF analyzers (Wiley/McLaren type) are discussed with regard to operation with ion desorption from a liquid matrix.     

Negative ion liquid secondary ion mass spectrometry of carbamate-linked oligodeoxynucleosides. II

Carbamate-linked Oligodeoxynucleosides, in which the backbone consists of carbamate and N-methylcarbamate linkages, have been analyzed by negative ion liquid secondary ion mass spectrometry. Bidirectional sequence-determining fragmentations are postulated to occur from a common radical anion intermediate that is produced by capture of an ionizing electron by the neutral sample molecule. Fragmentation reactions appear to be related to whether a proton or methyl group is present on the amide nitrogen.     

Characterization of beam-induced reactions occurring in liquid secondary ion mass spectrometry/fast-atom bombardment by tandem mass spectrometry

Department of General and Physical Chemistry, University of Liege, Liege, Belgium A specific beam-induced secondary reaction involving the condensation of hydroxylic matrices with some organic groups (aldehydes, ketones, etc.) accompanied by the loss of a water molecule was investigated by liquid secondary ion mass spectrometry/fast-atom bombardment (LSIMS/FAB). A mechanistic scheme and a structure of the induced product are proposed. The features of this secondary reaction were studied and the influence of the types of solutes, acidic additives, and matrices analyzed. Rather than a drawback, LSIMS/FAB mass spectrometry can take advantage of this matrix effect to infer analytical information through tandem mass spectrometry experiments. Specific neutral loss scans can be conducted to highlight beam-induced reactive molecules, even when the detection of these species is prevented in normal scan spectra by other surface-active components.     

Organic ion imaging beyond the limit of static secondary ion mass spectrometry

Secondary ion mass spectra and images were obtained from spikes of choline chloride, acetylcholine chloride, and methylphenylpyridinium iodide deposited onto specimens of porcine brain tissue. Samples were subsequently subjected to a dose of 10-keV Cs⁺ sufficient to suppress secondary ion emission characteristic of the targeted analytes. Following ablation of the samples by massive glycerol clusters generated by electrohydrodynamic emission, secondary ion mass spectra and images could be obtained that reflected the identity and location of the spiked analytes. The absolute intensity of secondary ion emission that followed ablation was found to be between 30 and 100% of the intensity obtained prior to exposure to the high dose of Cs’. Not all chemical noise is removed by ablation, however, so that the signal-to-noise ratios after ablation correspond to between 10 and 85% of their values observed under conditions of low primary ion dose.     

Polyelectrolytes as new matrices for secondary ion mass spectrometry

Significant enhancements in ion yields in time-of-flight secondary ion mass spectrometry (TOF-SIMS) are observed when water-soluble analytes are mixed with a polyelectrolyte, e.g., poly(diallyldimethylammonium chloride) or poly(sodium 4-styrenesulfonate), and then deposited in the layer-by-layer method on a surface. This previously unobserved effect is demonstrated for 5-chloro-8-methoxyquinoline appended diaza-18-crown-6, 5-(2-aminoethoxy)methyl-5-chloro-8-methoxyquinoline appended diaza-18-crown-6, acridine, 9-anthracenecarboxylic acid, and ferrocenecarboxylic acid. By optical ellipsometry film thicknesses range from ca. 5-20 angstroms. X-ray photoelectron spectroscopy shows significantly less analyte in the polyelectrolyte-analyte films than in the neat analytes. However, TOF-SIMS generally shows significant enhancements in ion yields from the polyelectrolyte films compared with either the neat compounds or the compounds solubilized with acid or base and then dried on a surface. These significant enhancements in ion yields also appear to extend to analyte fragments and cationized molecular species. Some enhancement is also observed for dried droplets of analytes mixed with a polyelectrolyte on surfaces.     

Lipid imaging with cluster time-of-flight secondary ion mass spectrometry

This brief article provides an overview of the current state of the art in biological imaging mass spectrometry using cluster time-of-flight secondary ion mass spectrometry (TOF–SIMS). Recent and spectacular improvements in terms of sensitivity of TOF–SIMS imaging methods have allowed many biological applications to recently be successfully tested, such as mapping of lipid disorders in human muscles of a patient suffering from dystrophy, localization of surfactins after the swarming of bacteria on a surface, or lipid mapping over whole-body animal sections.     

Structural characterization of reactive dyes using liquid secondary ion mass spectrometry/tandem mass spectrometry

Reactive Blue 19 (RB 19), its reactive form (RB 19-VS) and its hydrolyzed form (RB 19-OH) were examined using liquid secondary ion mass spectrometry/tandem mass spectrometry (LSIMS/MS/MS) in the negative-ion mode under low-energy collision conditions (240–300 eV). Structurally characteristic fragment ions were obtained, none of which has been previously reported for these reactive dyes. Among the ions obtained were SO₃^? ions, ions due to central amino cleavage and reactive group cleavage, and ions due to loss of SO₃ and SO₂. Possible pathways for the formation of product ions are proposed. The structural information obtained should help to characterize and identify reactive dyes better.