Selected trace and minor elements in Asunción soft rocks

Geochemical processes in soft immature rocks of the Asunción area are studied through X-ray fluorescense analysis of some trace and minor elements used as provenance indicators. Good correlation between light rare earth elements and other refractories were found and that the analytical data suggest inter alia an overall stable continental area setting.     

Über die Isolierung des Achilleins ausAchillea millefolium L. und dessen Identifizierung als Betonicin

Zusammenfassung Aus der heimischen PflanzeAchillea millefolium L. (Schafgarbe) wurde die als Glykoalkaloid beschriebene Base Achillein isoliert, charakterisiert und als Betonicin [1-Methyl-4-hydroxypyrrolidincarbonsäure-(2)-methylbetain] identifiziert.Mit 1 Abbildung     

Incompatible elements in bottom sediments of the Itaipú Dam Reservoir by EDXRF

Journal of Radioanalytical and Nuclear Chemistry - Sediments play an important role in the distribution of trace elements in the aquatic system and act as a sink for metals. Incompatible elements...     

Application of X-ray fluorescence analytical techniques in phytoremediation and plant biology studies

Phytoremediation is an emerging technology that employs the use of higher plants for the clean-up of contaminated environments. Progress in the field is however handicapped by limited knowledge of the biological processes involved in plant metal uptake, translocation, tolerance and plant–microbe–soil interactions; therefore a better understanding of the basic biological mechanisms involved in plant/microbe/soil/contaminant interactions would allow further optimization of phytoremediation technologies. In view of the needs of global environmental protection, it is important that in phytoremediation and plant biology studies the analytical procedures for elemental determination in plant tissues and soil should be fast and cheap, with simple sample preparation, and of adequate accuracy and reproducibility. The aim of this study was therefore to present the main characteristics, sample preparation protocols and applications of X-ray fluorescence-based analytical techniques (energy dispersive X-ray fluorescence spectrometry—EDXRF, total reflection X-ray fluorescence spectrometry—TXRF and micro-proton induced X-ray emission—micro-PIXE). Element concentrations in plant leaves from metal polluted and non-polluted sites, as well as standard reference materials, were analyzed by the mentioned techniques, and additionally by instrumental neutron activation analysis (INAA) and atomic absorption spectrometry (AAS). The results were compared and critically evaluated in order to assess the performance and capability of X-ray fluorescence-based techniques in phytoremediation and plant biology studies. It is the EDXRF, which is recommended as suitable to be used in the analyses of a large number of samples, because it is multi-elemental, requires only simple preparation of sample material, and it is analytically comparable to the most frequently used instrumental chemical techniques. The TXRF is compatible to FAAS in sample preparation, but relative to AAS it is fast, sensitive and multi-elemental. The micro-PIXE technique requires rather expensive instrumentation, but offers multi-elemental analysis on the tissue and cellular level.     

Ringschlussreaktionen an Pleiocarpa-Alkaloiden

Alkaloids with the pleiocarpin skeleton have been found to undergo ring closure on pyrolysis to give heptacyclic compounds with the kopsan (XI) carbon skeleton. Kopsinic acid (V), the main example, gave kopsanone (XIII). The structure XIII for kopsanone has been established by physical and chemical methods, degradation to the methine base XVII and reduction to kopsan (XI). A mechanism to explain these cyclizations is discussed.     

Performance of total reflection and grazing emission X-ray fluorescence spectrometry for the determination of trace metals in drinking water in relation to other analytical techniques

An intercomparison survey has been carried out in order to evaluate the performance of two related X-ray fluorescence techniques as compared to the achievements of several other analytical techniques applied for trace elements determination in drinking water. A relatively new technique, total reflection X-ray fluorescence (TXRF) and a novel related technique, grazing emission X-ray fluorescence (GEXRF) have been used for the analysis of a mineral water sample. The concentrations of the following elements have been determined: Na, Mg, K, Ca, Ni, Cu, Zn and Sr. The mineral water sample has also been analyzed by a number of other analytical techniques, routinely utilized in drinking water quality control. The analyses were performed in eleven laboratories which reported 286 individual determinations producing 75 laboratory means. From the obtained results, it can be concluded that the TXRF technique is suitable for a direct determination of heavy elements in drinking water (above potassium, Z = 19). This technique can compete with other analytical techniques routinely used in water quality monitoring. First results obtained with GEXRF spectrometry show that this technique can be successfully applied for the determination of low-Z elements in drinking water. However, results for sodium and magnesium were systematically too low, indicating that modifications of the quantification procedure may be required to improve the accuracy of determination for these light elements. Received: 5 January 1998 / Revised: 17 February 1998 / Accepted: 18 February 1998     

Performance of total reflection and grazing emission X-ray fluorescence spectrometry for the determination of trace metals in drinking water in relation to other analytical techniques

An intercomparison survey has been carried out in order to evaluate the performance of two related X-ray fluorescence techniques as compared to the achievements of several other analytical techniques applied for trace elements determination in drinking water. A relatively new technique, total reflection X-ray fluorescence (TXRF) and a novel related technique, grazing emission X-ray fluorescence (GEXRF) have been used for the analysis of a mineral water sample. The concentrations of the following elements have been determined: Na, Mg, K, Ca, Ni, Cu, Zn and Sr. The mineral water sample has also been analyzed by a number of other analytical techniques, routinely utilized in drinking water quality control. The analyses were performed in eleven laboratories which reported 286 individual determinations producing 75 laboratory means. From the obtained results, it can be concluded that the TXRF technique is suitable for a direct determination of heavy elements in drinking water (above potassium, Z = 19). This technique can compete with other analytical techniques routinely used in water quality monitoring. First results obtained with GEXRF spectrometry show that this technique can be successfully applied for the determination of low-Z elements in drinking water. However, results for sodium and magnesium were systematically too low, indicating that modifications of the quantification procedure may be required to improve the accuracy of determination for these light elements.     

Über die Kopplung eines Kapillargas-Chromatographen an ein Massenspektrometer mit Einrichtung für chemische Ionisation und die Registrierung der Gas-Chromatogramme mit einem Spektrenintegrator

Zusammenfassung Der einfache Selbstbau einer Kopplungseinrichtung für die direkte Kopplung eines Glaskapillarsäulen-Gas-Chromatographen an ein Massenspektrometer wird beschrieben. Die Konstruktion ist so gestaltet, daß ohne Umbau Spektren mit Elektronenstoß-oder chemischer Ionisation erhalten werden können. Die Darstellung der Gas-Chromatogramme erfolgt mit Hilfe eines Spektrenintegrators in guter Empfindlichkeit. Die Vorteile dieser Art der Registrierung bestehen darin, daß keine Doppelionenquelle und keine Splitbau teile benötigt werden. Massendurchläufe können zeitrichtig im Peakmaximum gestartet werden.

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Coupling a capillary gas chromatograph to a mass spectrometer with a derice for chemical ionisation and recording of gas chromatograms via a spectrum integrator

Summary The construction of a simple coupling device for the direct connection of a glass capillary gas chromatograph to a mass spectrometer is described. The construction is such that spectra with electron impact or chemical ionisation can be recorded without modification. The recording of gas chromatograms is performed by a spectrum integrator with good sensitivity. The advantages of this mode of plotting are that neither a dual ion source nor any splitting device is required. Mass scans can be started in the actual peak maximum.

     

Capabilities of elemental analysis by EDXRF for geochemistry

Elemental analyses of 10 geological samples from Morocco and some Standard Reference Materials were performed by Energy Dispersion X-Rays Fluorescence, Wavelength Dispersion X-Rays Fluorescence and Neutron Activation Analysis techniques in order to assess the accuracy and sensitivity of the concentrations determined with regard to requirements in geochemical exploration. The possibilities of utilization of EDXRF as an appropriate and economic technique for the analysis of various elements which are important in interpretation of geochemical data were evaluated.     

Detection of radionuclides from weak and poorly resolved spectra using Lasso and subsampling techniques

We consider a problem of identification of nuclides from weak and poorly resolved spectra. A two stage algorithm is proposed and tested based on the principle of majority voting. The idea is to model gamma-ray counts as Poisson processes. Then, the average part is taken to be the model and the difference between the observed gamma-ray counts and the average is considered as random noise. In the linear part, the unknown coefficients correspond to if isotopes of interest are present or absent. Lasso types of algorithms are applied to find non-vanishing coefficients. Since Lasso or any prediction error based algorithm is inconsistent with variable selection for finite data length, an estimate of parameter distribution based on subsampling techniques is added in addition to Lasso. Simulation examples are provided in which the traditional peak detection algorithms fail to work and the proposed two stage algorithm performs well in terms of both the False Negative and False Positive errors.