Progress in multi-ion counting spark-source mass spectrometry (MIC-SSMS) for the analysis of geological samples

Spark source mass spectrometry (SSMS) has experienced important and significant improvements in nearly all analytical features by the use of a multiple ion counting (MIC) system. Two procedures have recently been developed to further increase the analytical capabilities of MIC-SSMS in geochemistry. These are a mathematical correction of interferences, which is often necessary for the ultra trace element analysis of Nb, Ta, Zr, Hf and Y, and the development of an autospark system to hold the total ion beam constant. New analytical data for geological samples, especially international reference materials, are presented using the improved MIC-SSMS technique. The data set consists of high precision and low abundance data for Zr, Nb and Y in depleted reference materials. The MIC-SSMS results are compared with those of conventional SSMS using photoplates for ion detection. The precision of the MIC-SSMS isotope ratio measurements (about 1%) is more than a factor of 3 better than that of conventional SSMS, as demonstrated by analyses of Hawaiian samples. Total uncertainties of MIC-SSMS concentration data including all sources of error are generally between 2 and 5% for concentrations higher than about 0.3 microg/g and about 10% for trace element abundances in the ng/g range.     

A new spark source mass spectrometric technique for the analysis of sub-ng amounts of trace elements

Summary Spark source mass spectrometric tip-top-technique (TTT) is a new method for the analysis of sub-ng amounts of chemically separated trace elements in geological material. Besides its application to dissolved samples, TTT differs from conventional spark source mass spectrometry in reduction of measuring time (few minutes), photoplate background, and interferences by isobars and cluster-ions, resulting in enhanced sensitivities. Detection limits range from about 5 to 20 pg for the rare earth elements, U and Th, and from about 10 to 100 pg for noble metals. Precisions and accuracies of 1 to 5% are gained for trace elements abundances about 1 ng.A potential and especially useful application of TTT is the analysis of rocks available only in very small sample sizes and/or with very low concentration levels of trace elements. An additional application is the determination of osmium isotopes in geological material.

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Neues funkenmassenspektrometrisches Verfahren für die Analyse von sub-ng-Mengen von Spurenelementen

     

A coupled two-compartment model for immobilized enzyme electrodes

The effect of stirring on the transient and pseudo steady-state behavior of potentiometric and amperometric immobilized enzyme electrodes is accurately modelled by a coupled two-compartment system of nonlinear differential equations. In the first compartment, the enzyme layer, the chemistry is governed by enzyme kinetics and diffusion. This is coupled to the second compartment, the bulk solution, which is controlled only by molecular diffusion. Several results of analytical significance can be obtained by using this model: for example, it is shown how the stirring rate can be used to increase the linear dynamic range.     

Analysis of carbohydrates using different quaternized polystyrene-divinylbenzene particles and pulsed amperometric detection

Summary This paper reports on the use of a polymer-based, strong anion-exchange stationary phase for rapid, selective and sensitive analysis of physiological important mono-, di- and oligosaccharides by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) under alkaline conditions. The adsorbent was obtained by direct nitration of 3 and 5 μm, spherical non-porous highly cross-linked, styrene-divinylbenzene copolymer (PS-DVB) beads, followed by reduction of superficially introduced nitro groups with nascent hydrogen and quaternization of the resultant amino groups with iodomethane. Extended exposure to high pressure and strong alkaline conditions did not have any untoward effect on mechanical stability and chromatographic performance. A comparison of the 3 and 5 μm beads showed, that the synthesized 3 μm highly cross-linked PS-DVB particles are the preferred phases for the separation of monosaccharides and the 5 μm particles are preferable for the separation of oligosaccharides. To demonstrate the suitability for the analysis of complex samples, the optimized and validated system was used for the determination of glucose, fructose and sucrose in apple juice and other soft drinks such as Coca Cola. Finally, analysis within a few minutes without sample pretreatment down to a lower limit of detection of 0.174–0.504 μg mL⁻¹ at a linearity with R²>0.994 and a repooducibility higher than 98% further confirmed the efficiency of these polymeric sorbents.     

Exclusion limits on the WIMP-nucleon cross section from the cryogenic dark matter search

The Cryogenic Dark Matter Search (CDMS) employs Ge and Si detectors to search for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei while discriminating against interactions of background particles. CDMS data, accounting for the neutron background, give limits on the spin-independent WIMP-nucleon elastic-scattering cross section that exclude unexplored parameter space above 10 GeV/c2 WIMP mass and, at >75% C.L., the entire 3sigma allowed region for the WIMP signal reported by the DAMA experiment.     

Evidence for a biogenic, microorganismal origin of rock varnish from the Gangdese Belt of Tibet

In the present study we examined material from the Ashikule Basin of Tibet. Chemical analyses were performed by use of energy dispersive X-ray spectroscopy and electron probe microanalysis to clarify whether the varnish layers that had developed on the surface of the rhyolite are indeed composed of varnish bodies and silica glaze. Electron microscopic analyses revealed that the surface of the varnish is covered both by filamentous hyphae bacterial and cocci-shaped forms. Within the varnish mineral layer in those samples two forms of bacteria-like microorganisms exist; cocci as tightly packed bacterial aggregates [within varnish bodies], and bacillus-like microorganisms [within the varnish matrix, that surrounds the varnish bodies]. The bacillus-like forms are embedded in a network of filaments that have diameters between 35 and 45 nm. These bacilli with the surrounding filaments are assumed to have been involved in biofilm formation (synthesis of extracellular polymeric substances) prior to their live burial. We concluded that the formation of the varnish layers was for the most part biogenically driven by microorganisms.     

X-ray emission from clusters of galaxies and cosmological parameters

Clusters of galaxies are excellent probes of cosmic structure and evolution. X-ray studies of clusters provide some of their key parameters, viz., temperature of the hot intra-cluster gas, its metallicity, X-ray luminosity and surface brightness giving mass distribution and mass-flow rate in the case of cooling flows. X-ray measurements for a large sample of clusters have lead to estimates of the total gravitating mass in them, which can be compared to the virial masses derived from dynamical considerations and gravitational lensing in some of them. X-ray derived total masses are consistent with masses obtained from the other methods after the effects due to the presence of cooling flows are taken into account in the analyses. Estimated virial masses, lack of evolution in X-ray properties, and detection of several very hot clusters at high redshifts indicate a Universe with a low value (≤ 0.3) for the Ω parameter.     

Chemical mimicry: hierarchical 1D TiO2@ZrO2 core-shell structures reminiscent of sponge spicules by the synergistic effect of silicatein-α and silintaphin-1

In nature, mineralization of hard tissues occurs due to the synergistic effect of components present in the organic matrix of these tissues, with templating and catalytic effects. In Suberites domuncula, a well-studied example of the class of demosponges, silica formation is mediated and templated by an axial proteinaceous filament with silicatein-α, one of the main components. But so far, the effect of other organic constituents from the proteinaceous filament on the catalytic effect of silicatein-α has not been studied in detail. Here we describe the synthesis of core-shell TiO(2)@SiO(2) and TiO(2)@ZrO(2) nanofibers via grafting of silicatein-α onto a TiO(2) nanowire backbone followed by a coassembly of silintaphin-1 through its specifically interacting domains. We show for the first time a linker-free, one-step funtionalization of metal oxides with silicatein-α using glutamate tag. In the presence of silintaphin-1 silicatein-α facilitates the formation of a dense layer of SiO(2) or ZrO(2) on the TiO(2)@protein backbone template. The immobilization of silicatein-α onto TiO(2) probes was characterized by atomic force microscopy (AFM), optical light microscopy, and high-resolution transmission electron microscopy (HRTEM). The coassembly of silicatein-α and silintaphin-1 may contribute to biomimetic approaches that pursue a controlled formation of patterned biosilica-based biomaterials.     

Multi-responsive copolymers: using thermo-, light- and redox stimuli as three independent inputs towards polymeric information processing

We report on triple responsive polymers, exhibiting a distinct and reversible lower critical solution temperature in water that can be altered by light and redox stimuli, and we suggest their evaluation for molecular information processing.