Determination of tungsten in ores by energy dispersive X-ray fluorescence analysis

The possible determination of tungsten in low grade ores from Northern India, Rajasthan State has been explored by energy dispersive X-ray fluorescence analysis /EDXRF/ technique using radioisotope based excitation of W L X-rays and high resolution Si/Li/ detector system. Finely powdered ore has been diluted with optimal quantity of cellulose and converted into pellets to make it suitable for X-ray analysis after homogenization. The experiments have shown the minimum detectable limit of 33 ppm in diluted matrix. The results are compared with the spectrophotometric stannous chloride-thiocyanate method. EDXRF appears to be encouraging for routine and precise analysis of tungsten in low grade ores.     

Chemometric methods in energy dispersive X-ray fluorescence

Chemometric methods like principal component regression (PCR) are an excellent tool for the determination of matrix parameters from scattered radiation. PCR is used for the determination of carbon, hydrogen and oxygen from water and oil-based samples. This information is used in combination with fundamental parameters to determine zink in liquid samples. The method allows an accurate prediction of element concentrations in strong varying matrices.     

High energy electron impact ionization for elemental analysis by energy dispersive X-ray spectrometry

A method has been demonstrated in which the emission of characteristic X-rays following impact ionization by electrons of several MeV energy is used for quantitative elemental analysis. Because of the unique properties of MeV electrons with respect to their X-ray production yield and range in solids, the method has comparable sensitivity over a wide range of elements and relatively less stringent sample preparation requirements. By using energy dispersive techniques to detect the X-rays, a simultaneous determination of the weight fraction of the elements in an unknown sample is possible from a procedure based entirely on empirically determined relative X-ray yields. The method was tested by analyzing three standard metal alloy samples obtained from the National Bureau of Standards. Elements reaging from iron (Z=26) to lead (Z=82) with concentrations from 0.06% to 88% were quantitatively determined. In general, good approximate agreement was found wit the reported assays even for the minor constituents.     

Micro energy dispersive X-ray fluorescence analysis of polychrome lead-glazed Portuguese faiences

Several glazed ceramic pieces, originally produced in Coimbra (Portugal), were submitted to elemental analysis, having as premise the pigment manufacture production recognition. Although having been produced in Coimbra, their location changed as time passed due to historical reasons. A recent exhibition in Coimbra brought together a great number of these pieces and in situ micro Energy Dispersive X-ray Fluorescence (µ-EDXRF) analyses were performed in order to achieve some chemical and physical data on the manufacture of faiences in Coimbra.     

Biomedical applications of energy dispersive X-ray fluorescence

An X-ray fluorescence method for in vitro analysis of trace elements in biological samples is presented. The method is characterised by the use of an X-ray tube with secondary targets as a monoenergetic radiation source, and by thin specimens. The method has been applied to the analysis of blood serum samples, gunshot residue and urinary calculi.     

Soil characterization by energy dispersive X-ray fluorescence: sampling strategy for in situ analysis.

This work describes a sampling strategy that will allow the use of portable EDXRF (energy dispersive X-ray fluorescence) instruments for "in situ" soil analysis. The methodology covers a general approach to planning field investigations for any type of environmental studies and it was applied for a soil characterization study in the zone of Campana, Argentina, by evaluating data coming from an EDXRF spectrometer with a radioisotope excitation source. Simulating non-treated sampled as "in situ" samples and a soil characterization for Campana area was intended. "In situ" EDXRF methodology is a powerful analytical modality with the advantage of providing data immediately, allowing a fast general screening of the soil composition.     

Mathematical techniques for quantitative elemental analysis by energy dispersive X-ray fluorescence

Recent interest in the use of automated or semi-automated energy dispersive X-ray fluorescence analysis has created the need for improved mathematical techniques and computer software for use with this type of analysis. The present paper reviews the efforts to date to develop the mathematical techniques necessary for implementing: (1) the library least-squares method for the determination of characteristic elemental X-ray intensities and (2) the use of the Monte Carlo method for extending the fundamental parameters approach to radioisotope and X-ray machine exciting sources for the determination of elemental amounts.     

Analysis of nuclear materials by energy dispersive X-ray fluorescence and spectral effects of alpha decay

Energy dispersive X-ray fluorescence (EDXRF) spectra collected from alpha emitters are complicated by artifacts inherent to the alpha decay process, particularly when using portable instruments. For example, ²³⁹Pu EDXRF spectra exhibit a prominent uranium L X-ray emission peak series due to sample alpha decay rather than source-induced X-ray fluorescence. A portable EDXRF instrument was used to collect qualitative spectra from plutonium and americium, and metal alloy identification was performed on a Pu-contaminated steel sample. Significant alpha decay-induced X-ray fluorescence peaks were observed in spectra obtained from the plutonium and americium samples due to the ²³⁵U and ²³⁷Np daughters, respectively. The plutonium sample was also analyzed by wavelength dispersive XRF (WDXRF) to demonstrate that alpha decay-induced X-ray emission has a negligible effect on WDXRF spectra.     

Improved digital filtering for automated spectral deconvolution in energy dispersive X-ray fluorescence analysis

For the quantitation of overlapping peaks in energy dispersive X-ray fluorescence analysis, a computer program has been developped. It is based on a linear least-squares deconvolution of digitally filtered spectra. The performance of five different filters was studied on simulated spectra with respect to systematic and random errors. It is concluded that a symmetric, zero-weighted filter consisting of a Gauss-shape central lobe and a negative constant involving an energy range of 280 eV gives optimal results. The random error introduced by the filtering procedure is very moderate, so that the total error is only slightly above the value predicted from theory. A series of difficult analytical situations (S/Mo; S/Pb; Ti/V/Ba) are treated satisfactorily. Explantations for problems experienced in the literature are suggested.     

Rapid identification of inorganic salts using energy dispersive X-ray fluorescence.

A simple method for the rapid identification of inorganic salts used as raw materials during food production has been established using energy dispersive X-ray fluorescence (EDXRF). Intensities of Na, Mg, P, S, Cl, K, Ca, Mn, Fe, Cu, Zn Kalpha peaks have been measured. The treatment and comparison of the respective intensities allowed a rapid identification of inorganic salts. Two different methods of data treatment have been tested: K nearest neighbours (KNN) and centroids. Using cross validation on a database containing 140 samples representing 31 classes, a total of 98% of samples were well identified.     

Quantitative energy dispersive X-ray microanalysis of electron beam-sensitive alloyed nanoparticles.

An energy dispersive X-ray spectrometry (EDXS) method is developed to evaluate the composition of alloyed nanoparticles (NPs) where one of the alloying elements is removed under the electron beam during microanalysis with a transmission electron microscope (TEM). The method is demonstrated for alloyed Au-Ag NPs of a diameter ranging from 6 to 20 nm produced by laser evaporation of a water-suspended Ag-Au powder mixture of varying composition. Series of EDXS spectra are recorded for 30 NPs from samples with five different Ag:Au ratios revealing Ag depletion from NPs during electron irradiation. By studying the evolution of NPs composition as a function of dose, the initial Ag content for each NP is extrapolated. The rate of Ag depletion is discussed in terms of sputtering and knock-on damage. On average, approximately one Ag atom is lost from the NP for each Ag L X-ray detected. To assess the limitations of microanalysis in these sensitive nanoscale structures, the concept of detectability limit is adapted to our method. This benchmark is then evaluated for Ag in Au-Ag NPs of various sizes and acquisition times. This study should be regarded as a guide for the design of analytical TEM measurements of beam-sensitive NPs.     

Determination of carrier yields for neutron activation analysis using energy dispersive X-ray spectrometry

A new method is described for determining carrier yield in the radiochemical neutron activation analysis of rare-earth elements in silicate rocks by group separation. The method involves the determination of the rare-earth elements present in the carrier by means of energy-dispersive X-ray fluorescence analysis, eliminating the need to re-irradiate samples in a nuclear reactor after the gamma ray analysis is complete. Results from the analysis of USGS standards AGV-1 and BCR-1 compare favorably with those obtained using the conventional method.     

Quantitative energy dispersive X-ray analysis of submicrometric particles using a scanning electron microscope

The quantitative scanning electron microscope-energy dispersive X-ray (SEM-EDX) analysis of a horneblende and two augite prismatic samples reduced to submicrometric particles was performed, and error due to the particle effects ("absent mass" and the "reduced absorption" effect) was minimized. Correction factors as a function of fragment size were obtained for O, Na, Mg, Si, Ca, and Fe. In addition, the influence of chemical composition of the samples used as standards (the matrix effect) on correction factors was evaluated. The results indicate that the absent mass effect is dominant for all elements except for the light elements O and Na, for which the reduced absorption effect is dominant. No significant matrix effect has been observed. By using corrected SEM-EDX data, the error on quantification of the element concentration has been estimated to be 3% relative for light elements and below 2% relative for heavy elements (notably, about 1% relative for Fe).     

Multilayer characterization by energy dispersive X-ray reflectivity technique

An experimental setup was developed to verify the feasibility of silicon drift detector to be used for the multilayer characterization by means of multilayer energy dispersive X-ray reflectivity. Such a detector allows high count rates up to 3 × 10⁵ cps and can be used in principle for the direct beam intensity measurement, which is to be done for the X-ray multilayer reflectivity patterns obtaining. A series of measurements were performed for Mo/B₄C multilayer sample. A quality of the experimentally obtained data turns out to be enough to perform a sample structure exploration using a numerical procedure of experimental data fitting. Due to low cost and short time, required for the measurements, an experimental technique proposed has a good perspective to be used for some practical applications in industry.     

X-ray chemical shift determination by energy dispersive detection

X-ray energy shifts due to differences in the chemical states of the emitting elements were investigated. The centroids of the Kα and Kβ characteristic lines produced from chromium and manganese compounds were measured and compared with the centroids of X-ray lines produced from the corresponding metals. Excitation was carried out using a ¹⁰⁹Cd radioactive source, and the X-rays were detected with use of a Si(Li) energy dispersive semiconductor detector. solver, a program included in Microsoft Excel for Windows, was used to approximate the form of the X-ray lines with a gaussian function. The results showed that energy dispersive X-ray detection can be used for chemical shift determinations.     

Analysis of uranium ores by energy dispersive X-ray fluorescence

Summary The determination of uranium in ores by energy-dispersive X-ray fluorescence (XFA) is demonstrated for uranium ore samples of known content. For calibration silica gel standards are used. Matrix effects are corrected by measuring the Compton scattering peaks. The radionuclide ¹⁰⁹Cd as well as a X-ray tube in combination with Mo or Sn as secondary targets are suited as X-ray sources. The mean relative deviation of the values found from the given values is 5%

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Analyse von Uranerzen mit Hilfe der energiedispersiven Röntgenfluorescenz

Zusammenfassung Die Anwendbarkeit der energiedispersen Röntgenfluorescenzanalyse zur Bestimmung des Urangehaltes in Erzen wird am Beispiel von Uranerzproben bekannten Gehaltes demonstriert. Für die Eichung werden Kieselgel-Standards verwendet. Die Matrixeffekte werden mit Hilfe der ComptonStreupeaks korrigiert. Als Röntgenquellen eignen sich sowohl eine ¹⁰⁹Cd-Radionuklidquelle als auch eine Röntgenröhre mit Mo oder Sn als Sekundärtarget. Die mittlere relative Abweichung der Analysenwerte von den gegebenen Werten beträgt 5 %.

     

Determination of nickel in lateritic ore by various techniques of energy dispersive X-ray fluorescence analysis

Radiometric techniques of determining the nickel content in lateritic ore samples are described. In some of the methods proposed a semiconductor detector and a multichannel pulse height analyzer are required. In another technique simple portable equipment with a proportional counter was used. Calculation methods of correction for matrix effects were applied, in combination with measurements of the fluorescence to scatter ratio and the use of edge filters.     

Energy dispersive X-ray fluorescence analysis of gallstones

The elemental analysis of south Indian gallstones has been carried out using energy dispersive X-ray fluorescence (EDXRF) spectroscopy. A number of important elements including Fe, Cu, Zn, Br, and Pb were estimated from the EDXRF spectra. The results are presented and discussed.     

Characterization of Japanese color sticks by energy dispersive X-ray fluorescence,X-ray diffraction and Fourier transform infrared analysis

This work comprises the use of energy dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) techniques for the study of the composition of twentieth century traditional Japanese color sticks. By using the combination of analytical techniques it was possible to obtain information on inorganic and organic pigments, binders and fillers present in the sticks. The colorant materials identified in the sticks were zinc and titanium white, chrome yellow, yellow and red ochre, vermillion, alizarin, indigo, Prussian and synthetic ultramarine blue. The results also showed that calcite and barite were used as inorganic mineral fillers while Arabic gum was the medium used. EDXRF offered great potential for such investigations since it allowed the identification of the elements present in the sample preserving its integrity. However, this information alone was not enough to clearly identify some of the materials in study and therefore it was necessary to use XRD and FTIR techniques.