Online monitoring of aerosols with an energy-dispersive X-ray spectrometer

A continuously working sampling and analyzing device was developed and tested. It is suitable for monitoring of metals bound to particulate matter in emissions of stack gases. The samples were precipitated on a pure quartz fiber filter tape and analyzed shortly afterwards non-destructively by an energy dispersive X-ray spectrometer (EDXRS). By using this method a wide range of elements with atomic numbers from 19 (K) to 82 (Pb) can be analyzed. New experiments have shown that the novel combined particle sampling and analysis system (X-DUST) could also successfully be used for the monitoring of toxic elements in ambient air.     

Estimation of the properties of an energy-dispersive X-ray fluorescence spectrometer based on a composite double-layer detector

A mathematical model of double-layer Si-Ge and Si-AsGa energy-dispersive detectors of X-rays based on the analysis of processes of radiation and electron transfer in the detector is proposed along with a model of an energy-dispersive X-ray fluorescence spectrometer on the basis of this detector. The probabilities of recording of photons in different sections of the detector response function are calculated using the Monte-Carlo technique. It is shown that, in using an anticoincidence circuit and a Si detector as the first layer and Ge or AsGa detectors as the second layer, a detector with improved characteristics can be obtained, namely, the suppressed loss peaks of Ge or As and Ga and the efficiency of detection at the high radiation energy close to that of the Ge or AsGa detector. This detector in the energy-dispersive X-ray fluorescence spectrometer in some cases allows the reduction of the background level.     

X-ray spectroscopy with an ESCA spectrometer

The use of photoelectron emission from clean solid surfaces of low-Z elements for soft X-ray spectroscopy is demonstrated. The measurement made on a clean graphite sample in an ESCA spectrometer using X-ray emission from a stainless-steel anode is promising enough to attempt the use of the technique for time-resolved X-ray spectroscopy of transient plasmas.     

ArtTAX - a new mobile spectrometer for energy-dispersive micro X-ray fluorescence spectrometry on art and archaeological objects

A newly developed spectrometer for energy-dispersive micro X-ray fluorescence spectrometry has been designed for the demands of archaeometry. ArtTAX combines the advantages of non-destructive and sensitive multi-elemental analysis at sub-mm resolution with the possibility of working outside the laboratory. The spectrometer consists of an air-cooled, low-power molybdenum tube, new generation polycapillary X-ray optics, a silicon drift detector without the need for liquid-nitrogen cooling, a CCD camera, and three light diodes for sample positioning. The motor-driven measurement head is fixed on a x,y,z-flexible tripod support which can be assembled and dismantled within minutes. The spot size of the primary X-ray beam was determined to be 94 microm for the Cu(Kalpha) energy, the detection limits are in a range of a few tens of microg g(-1) for the medium energy-range in glass. Additional open helium purging in the excitation and detection paths enables the determination of elements down to sodium, thus avoiding vacuum conditions or a size-limiting sample chamber. A selection of qualitative and quantitative results on pigment, metal, glass, and enamel analyses are presented to show the potential of ArtTAX in the field of art and archaeology.     

Qualitative identification of alloys by energy-dispersive X-ray spectroscopy

Energy dispersive X-ray spectroscopy can be used to identify alloy types quickly and, in many cases, to distinguish between alloy systems within a certain alloy type. Characteristic X-rays of major components in an alloy are produced through excitation by an isotopic source. Ratios of the X-ray intensities of a pair of elements are plotted vs. ratios of the theoretical weight fractions of these elements. This provides a unique data point which is a function of the composition of the particular alloy system. In some cases, characteristic X-rays of minor constituents are used for total identification.     

Automated energy-dispersive X-ray fluorescence analysis of environmental samples

Summary A procedure is described for the routine automatic analysis of 20 elements in small environmental samples. Up to 50 samples a day can be processed. The instrument uses an energy dispersive X-ray spectrometer for the simultaneous detection of all elements during a 5–20 min measurement. Computer techniques are used for the subsequent data reduction of the X-ray spectra. The technique is applicable to air particulate matter filtered from the air, to suspended material in water which is filtered on a filter paper and to dissolved trace elements which are evaporated on filter paper or are collected on a thin ion-exchange loaded paper.

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Automatisierte energie-dispersive Röntgenfluorescenzanalyse von Umweltmaterial

Zusammenfassung Ein Verfahren zur automatischen Routinebestimmung von 20 Elementen in Umweltmaterial wird beschrieben. Bis zu 50 Proben je Tag können verarbeitet werden. Ein energie-dispersives Röntgenspektrometer wird zur simultanen Erfassung aller Elemente bei einer Messung von 5–20 min benutzt. Die nachfolgende Auswertung der Spektren wird mittels Computer durchgeführt. Das Verfahren findet Anwendung auf Schwebestaub oder in Wasser suspendierte Substanzen, die auf Filterpapier gesammelt wurden sowie auf gelöste Elementspuren, die auf Filterpapier getrocknet oder durch Ionenaustauschpapier angereichert wurden.

     

Thermal analysis of ammonium nitrate by energy-dispersive X-ray diffraction

Ammonium nitrate was heated and cooled in consecutive steps in a high temperature device mounted on a X-ray goniometer. Diffraction patterns were measured at each temperature, using a Si-Li detector together with a multichannel analyzer. The results strongly support the existence of a phase II'. They show that the phase change IV/III goes via a transition state similar to or consistent with phase II'.

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Zusammenfassung Ammoniumnitrat wurde in einer Hochtemperaturkammer auf einem Röntgengoniometer schrittweise aufgeheizt und abgekühlt. Bei jeder Temperatur wurde ein Beugungsdiagramm aufgenommen mit einem Si-Li-Detektor und angeschlossenem Vielkanalanalysator. Die Ergebnisse unterstützen die Annahme einer Phase II'. Sie zeigen, daß die Phasenumwandlung IV/III über einen Übergangszustand verläuft ähnlich oder identisch mit der Phase II'.

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Résumé Le nitrate d'ammonium était chauffé et refroidi pas à pas dans un four fixé sur un goniomètre de rayons X. A chaque température, des diagrammes de diffraction étaient mesurés par un détecteur semiconducteur, combiné avec un sélecteur multicanaux. Les résultats supportent l'existence d'une phase IF. Ils montrent, que la transition des modifications IV/III procède par une phase de transition, qui ressemble à la phase II'.

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, . , Si-Li . II. , IV/III , II.

     

Non-destructive analysis of archeological samples by energy-dispersive X-ray fluorescence

Summary A non-destructive method is described for the determination of major and minor constituents in archeological specimens by energy-dispersive X-ray fluorescence. Homogeneity tests are made by measuring at various sites of the specimen. In the same way, mean values are obtained for inhomogeneous specimen without taking samples. For calibration, powder standards are used. In case of the determination of elements with numbers up to 14 (Si) a vacuum chamber is used and the dimensions of the specimens are limited by the dimensions of that vacuum chamber, whereas for the determination of elements from K up to U specimens of any size, form or weight are suitable.

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Zerstörungsfreie Analyse von archäologischen Proben mit Hilfe der Energie-dispersiven Röntgenfluorescenzanalyse

Zusammenfassung Eine zerstörungsfreie Methode für die Bestimmung von Haupt- und Nebenbestandteilen in archäologischen Proben mit Hilfe der Energie-dispersiven Röntgenfluorescenzanalyse wird beschrieben. Für Homogenitätstests wird an mehreren Stellen der Probe gemessen. In der gleichen Weise werden für inhomogene Proben Mittelwerte erhalten ohne Probenahme. Für die Eichung werden Pulverstandards verwendet. Im Falle der Bestimmung von Elementen mit Ordnungszahlen bis 14 (Si) wird eine Vakuumkammer eingesetzt, und die Dimensionen der Proben sind durch die Dimensionen dieser Vakuumkammer begrenzt, während für die Bestimmung der Elemente K bis U Proben jeder Größe, jeder Form oder jeden Gewichts verwendbar sind.

     

Microanalysis of polymers using a windowless energy-dispersive X-ray detector

The surface compositions of various polymeric films, grown electrochemically on platinum foils, have been investigated by energy-dispersive x-ray analysis in conjunction with scanning electron microscopy (SEM/EDS). Comparison of the relative area ratios of peaks for the C and N K_emission lines show that the EDS may be used to study the surface composition of polymers. The evidence presented strongly suggests that there is limited structural degradation and the elemental composition is not changed under the electron beam at relatively low accelerating voltages. This technique statistically samples the repeat units of the polymer. For samples grown in both aqueous and nonaqueous solutions. SEM/EDS provides evidence for extensive contamination with oxygen.     

Comparison of two different approaches to calibrate an energy-dispersive x-ray fluorescence spectrometer for the analysis of aerosol-loaded filters

The quantitative analysis of aerosol loaded filters by x-ray fluorescence spectroscopy implies the use of calibration curves obtained from synthetic standards. Two preparation methods to obtain these calibration samples are described and compared, showing that matrix and enhancement effects are neglible for membranous filters and that both calibrations lead to acceptable results. Calibration standards produced via an aerosol generator always lead to a greater sensitivity compared to the standard produced with droplets. The filters resist the conditions of replicated measurements.     

Comparison of two different approaches to calibrate an energy-dispersive x-ray fluorescence spectrometer for the analysis of aerosol-loaded filters

The quantitative analysis of aerosol loaded filters by x-ray fluorescence spectroscopy implies the use of calibration curves obtained from synthetic standards. Two preparation methods to obtain these calibration samples are described and compared, showing that matrix and enhancement effects are neglible for membranous filters and that both calibrations lead to acceptable results. Calibration standards produced via an aerosol generator always lead to a greater sensitivity compared to the standard produced with droplets. The filters resist the conditions of replicated measurements.     

Trace metal analysis in arctic aerosols by an inductively coupled plasma-time of flight-mass spectrometer combined with an inductively heated vaporizer

Two newly developed instruments were combined to analyze the trace metal content in size separated arctic aerosols during the measurement campaign ASTAR 2004 (Arctic Study of Tropospheric Aerosols, Clouds and Radiation 2004) at Spitsbergen in May–June 2004. The aim of this extensive aerosol measurement campaign was to obtain a database for model-calculations of arctic aerosol, which play an important role in the global climate change. The ASTAR project was centered on two aircraft measurement campaigns, scheduled from 2004 to 2005, addressing both aerosol and cloud measurements, combined with ground-based and satellite observations. In the present paper one example for the analysis of ground-based aerosol particles is described. The sampling of aerosol particles was performed in a well-known manner by impaction of the particles on cleaned graphite targets. By means of a cascade impactor eight size classes between 0.35 and 16.6 μm aerodynamic diameters were separated. To analyze the metal content in the aerosol particles the targets were rapidly heated up to 2700 °C in an inductively heated vaporizer system (IHVS). An argon flow transports the vaporized sample material into the inductively coupled plasma (ICP) used as ionization source for the time of flight-mass spectrometer (TOF-MS). The simultaneous extraction of the ions from the plasma, as realized in the TOF instrument, allows to obtain the full mass spectrum of the sample during the vaporization pulse without any limitation in the number of elements detected. With optimized experimental parameters the element content in arctic aerosol particles was determined in a mass range between ⁷Li and ²⁰⁹Bi. Comparing the size distribution of the elemental content of the aerosol particles, two different meteorological situations were verified. For calibration acidified reference solutions were placed on the cleaned target inside the IHVS. The limits of detection (LOD) for the element mass on the target range between 2 and 200 pg for the elements studied, except Na, Mg, and Cr, which are influenced by high background.     

Procedure for background estimation in energy-dispersive X-ray fluorescence spectra

A method for semi-automatic background estimation in energy-dispersive x-ray fluorescence spectra is outlined. Two cubic splines were investigated and the spline called the Butland interpolant was chosen for further investigation. Prior to the calculation of the spline, peak regions are set up, and suitable knots are defined outside the peak regions. To set up the peak regions, an automatic peak-search routine and a calibration equation are used. For a given peak, the latter relates the full width at half maximum (FWHM) to the peak centre. In turn, the size of the peak regions are defined by the FWHM multiplied by a constant given by the user. The method was tested on several types of spectra. It was found that the optimal size of the peak region decreased with increasing peak density. Reproducibility tests showed that the standard deviation of the summation of counts within a peak region and after background subtraction was less than would be expected from the counting statistics.     

Analysis of Jamaican soils and sediments by energy-dispersive X-ray fluorescence spectrometry

The calibration of a tube excited Energy-Dispersive X-Ray Fluorescence spectrometer for routine geochemical analyses of Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Rb, Sr and Pb in Jamaican soils and sediments is described. Simple linear and parabolic regression models using scattered radiation and an element as internal standards were applied. The analysis of over 200 samples from a regional soil survey has been used to contribute to a database on the geochemistry of Jamaican soils and sediments. An application example of the Zn distribution map in Jamaican soils is presented.