X-ray Fluorescence Analysis Techniques Research Articles

Assessment of the possibility of X-ray fluorescence analysis before conducting the experimental work

The article proposes an approach to the development of a method for X-ray fluorescence analysis of an object using crystal-diffraction spectrometers prior to the experimental work. In case when the X-ray fluorescence analysis method is intended as a substitute for an existing method, then for the object being analyzed the statistical characteristics of the material for which the X-ray fluorescence analysis method is being developed, i.e. the average content of the elements to be determined, the dispersion and the range of the elements content, the requirements for the accuracy of determination, and some others, are calculated on the basis of archival data of the analytical laboratory (or an array of selected calibration samples). In case when a new method is developed, technical requirements for the product allowing estimating these characteristics are sufficient. Analytical characteristics, such as basic instrumental error, sensitivity, spectral resolution, contrast, must be measured and calculated over the entire operating range of the measured analytical lines for the spectrometer used. Metrological characteristics of the method for determining the elements, i.e. detection limit, differential sensitivity, instrumental reproducibility of content measurement at the selected exposure time, are evaluated on the basis of these data. At this stage the question concerning the necessity of diluting the samples with a heavy or light diluent for obtaining satisfactory differential sensitivity may be resolved. The regimes for recording the analytical signal for the elements to be analyzed, i.e. analytical lines, analyzer crystals, X-ray tube operating modes, are determined, the probability of overlapping spectral lines is estimated, and the background measurement points are selected. Calculation of theoretical and simulation of experimental intensities for selected calibration and test samples and calculation of theoretical coefficients of influence are carried out. The expected error of the analysis is estimated on the basis of the statistical characteristics of the material and the theoretical coefficients of influence, and the need to take into account the relationship between the interfering elements in the equations is determined for achieving the required accuracy of determining the elements. Selection of regression or theoretical coupling equations, which provide the required accuracy of determining the elements, is carried out on the basis of the simulated experimental intensities of the analytical lines of the elements. Such approach allows a priory estimate the possibility of developing an X-ray fluorescence analysis technique for an object selected, and can significantly reduce time for performing the experimental work. Keywords: X-ray fluorescence analysis, method of analysis, analyzed object, X-ray spectrometer, analysis characteristics, forecast of experimental intensities, estimation of expected error, modes of registration of the analytical signal, coupling equations.

Operando X-Ray Fluorescence Measurement Method of Cerium Radical Quencher Distribution in through-Plane MEA

Hydroxyl and hydroperoxyl radicals produced by reacting impurities with hydrogen peroxide is one of the degradation factors of polymer electrolyte [1]. A method to suppress this degradation is the addition of cerium into the polymer electrolyte membrane (PEM), which serves as radical quencher [2,3]. However, cerium ion in PEM migrates from the initial state by fuel cell operation [4]. The lack of cerium ion in PEM causes degradation from radical species. Information on cerium migration in PEM is necessary to design the membrane electrode assembly (MEA) for long-term operation. Although the observation of cerium ion diffusion with in-plane direction of PEM has been reported [5], it is difficult to detect the distribution in through-plane of MEA under fuel cell operating condition due to the quite narrow thickness of PEM. This study reports an operando X-ray fluorescence analysis technique to detect cerium distribution in through-plane direction of MEA using high-energy X-ray nanobeam.MEAs were prepared by a conventional method using Pt/C catalyst and polymer electrolyte with the thickness of 12 mm. The active electrode area was 1 cm2. Single cells were assembled using custom-made end-plates that have an X-ray permeation window. Operando X-ray fluorescence spectroscopy measurements were performed at SPring-8, BL37XU (Japan). The monochromatized X-ray at an energy of 45 keV was focused to less than 200 nm by Kirkpatrick-Baez mirror. To detect the cerium distribution in MEA, Ce-Ka fluorescence intensity was counted using a Ge semiconductor detector with scanning the position of the cell. The cell temperature was 80 ℃. O2 and H2 gases with relative humidity of 100% were flew to cathode and anode, respectively.Figure 1 shows line-scan profile of Ce-Kα fluorescence X-ray intensity from the as-prepared MEA. The x-axis represents the through-plain position, where the positive and negative sides corresponds to cathode and anode sides, respectively. The two peaks are observed at 678 and 685 mm and the peak width is approximately 13 mm. This peak shows PEM containing cerium ion. During the fuel cell operation, the line-scan is repeated and cerium ion distribution can be analyzed. Acknowledgment Part of this work is based on results obtained from the project commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.[1] R. Borup et al., Chem. Rev., 107 3904-3951 (2007).[2] E. Endoh et al., ECS Electrochem. Lett. 2 F73-F75 (2013).[3] P. Trogadas et al., Electrochem. Solid-State Lett. 11 B113-B116 (2008).[4] S.M. Stewart et al., ECS Electrochem. Lett. 3 F19-F22 (2014).[5] A.M. Baker et al., J. Electrochem. Soc. 164 F1272-F1278 (2017). Figure 1

Experimental and theoretical approaches for determining the K-shell fluorescence yield of carbon

The knowledge of atomic fundamental parameters, such as the fluorescence yields with low uncertainties, is of decisive importance in elemental quantification involving X-ray fluorescence analysis techniques. However, especially for the low-Z elements, the available data in the literature is either of poor quality, of unknown or very large uncertainty, or both. For this reason, the K-shell fluorescence yield of carbon was determined in the PTB laboratory at the synchrotron radiation facility BESSY II. In addition, theoretical calculations of the same parameter were performed using the multiconfiguration Dirac–Fock method, including relativistic and quantum electrodynamics (QED) corrections. Both values obtained in this work are compared to the corresponding available published data.

Applying rail transit construction waste to make building materials: using the theory of sustainable development.

With the rapid development of the rail industry, a large amount of construction waste will be generated during the construction phase, posing a significant risk of environmental pollution and exacerbating the plight of global resource shortages. This study establishes a green disposal system for rail transportation based on the theory of sustainable development. Shield slag, shield weathered sand, shale, and engineering slag are used as raw materials, and sintered bricks are adopted as their innovative disposal method. The heavy metals in the four types of construction waste and recycled products were tested by X-ray fluorescence analysis technique to analyze the actual environmental pollution risk and explore the influence of the firing stage on the performance of the recycled products through the enrichment factor evaluation method. The results of the physical and chemical property tests of the fired samples showed that the environmental pollution risk of the four recycled products after firing was at a low-risk level (EF < 2), the strength test results showed that the best specimens had a strength rating of 20MPa and the other performance indicators (frosting degree, lime bursting test) measured also met the requirements of the recycled bricks. This study achieves the harmless treatment of construction waste, provides a disposal system for the green recycling of construction waste from rail transport, and provides a theoretical basis for subsequent studies on the effects of different external conditions on such recycled products.

Focusing capillar and porous X-ray optics

The paper discusses the principles and capabilities of X-ray focusing capillar and porous optics. Special attention is paid to polycapillar optics, confocal technique of X-ray fluorescence analysis, as well as wide-angle &amp;quot;lobster eye&amp;quot; optics. Keywords: X-rays, focusing, capillar, porous optics, &amp;quot;lobster eye&amp;quot; optics.

Study of confocal 3D micro X-ray fluorescence analysis technique based on polycapillary X-ray lens

This study realized the microcell analysis using confocal area formed by a pair of polycapillary X-ray lens, built a 3D micro X-ray fluorescence spectrometer, elaborated the controlling software, and analyzed the 3D scan performance of the set-up via its measured and calculated basic parameters. The depth-detecting performance of the developed set-up was assessed by scanning several samples of Cu-Mo thin film on silicon base and red-green porcelain of Ming dynasty under different conditions. In addition, through surface-adaptive scanning, the scanning and identification of the fractures and fine cracks of the ceramic samples revealed the morphology of samples, which was consistent with the theoretical model.

The application of EDXRF on soil heavy metal analyzation in a planting area

With the increase of heavy metal concentration in soil, serious environmental problems have arisen. At present, heavy metals mainly refer to biotoxic heavy metals, including Lead, Cadmium, Mercury and Chromium, etc., which are produced in large quantities by human activities and difficult to be degraded, resulting in their loss of original activity and chronic poisoning because of the reaction with proteins and enzymes in human body. The soil concentration in the planting area exceeds the standard and is enriched in human beings, animals and plants, which directly endangers the living environment and health. In this paper, the soil in the planting area next to Xiangzhang canteens of Chengdu University of Technology was selected for field investigation, and the data analysis and risk assessment were carried out after testing the concentration of heavy metals in the surrounding soil through reasonable sampling, sample treatment and Energy-Dispersive X-ray fluorescence analysis techniques.

X-ray analysis in the study of sorption processes on clinoptilolites used as geochemical barriers

Kinetics of Sr2+sorption from potable water on clinoptilolite tuffs (CLPT) of different deposits (Honguruu (Yakutia), Holinskoe (Transbaikalia) and white Plast (Bulgaria)) is studied in detail. A technique of X-ray fluorescence analysis (XRF) is developed to determine the chemical composition of CLPT from a small sample (0.05 – 0.1 g). The emitters are prepared by pressing 10-mm tablets from the initial material added with polystyrene as a binder in a weight ratio 5:1. Reference standards (reference standards of composition) of rocks close in chemical composition to the CLPT are used for calibration. Using the empirical model of α-correction, the equations are derived to calculate the content of macro components of the sample in the «saturated» layers. To calculate the strontium content in the «intermediate» layers for the CLPT from different deposits the correction equations are derived. It is shown that the correction equation can be the same for all the CLPT used in the experiment. Kinetics of Sr2+sorption on CLPT consists of 3 stages: (a) the intra-diffusion process, described by the coefficient of internal diffusion, (b) deceleration of the sorption process, described by the corresponding kinetic coefficient, and c) secondary increase in Sr2+sorption which terminates when the equilibrium is reached. The results can be used to develop a mathematical model describing the dynamics of the ion-exchange process on CLPT in NH4form from dilute solutions.

Experimental and theoretical determination of the L-fluorescence yields of bismuth

The knowledge of atomic fundamental parameters such as the mass attenuation coefficients or fluorescence yields with low uncertainties, is of decisive importance in elemental quantification involving x-ray fluorescence analysis techniques. For example, several databases giving the mass attenuation coefficients are accessible and frequently used within a large community of users. These compilations are most often in good agreement for photon energies in the hard x-ray ranges. However, they significantly differ for low photon energies and around the absorption edges of the elements. Some review articles present compilations of measured fluorescence yields values found in the literature. However reliable measurements are not so many illustrating the inherent difficulties. Mass attenuation coefficients of bismuth were determined experimentally in the photon energy range from 100 eV to 30 keV by using monochromatized synchrotron radiation at SOLEIL (France). The fluorescence yields of the three L-subshells of bismuth were also determined using a reflection geometry setup. The application of high-accuracy experimental techniques resulted in low uncertainty mass attenuation coefficients and L-subshell fluorescence yields that are directly compared to existing databases and with updated relativistic configuration mixing Dirac–Fock calculations including QED corrections.

Nuclear activation analytical methods and X-ray fluorescence analysis in application to determination of pollutants and trace elements in food and for studying biokinetics of nanoparticles

For assurance of food quality and safety, it is necessary to control routes of food pollutants, including toxic trace elements in all stages of handling, ranging from the production of agricultural products, including the processing, storage, transportation, and ending with cooking and consumption. For this control the nuclear activation analytical methods (NAAMs) and X-ray fluorescence analysis (XRFA) are studied and developed for the detection of chemical elements in different environments. NAAMs involve two stages: the activation of nuclear isotopes with thermal neutrons or fast charged particles and gamma spectrometry. XRFA technique is based on detecting characteristic fluorescent X-rays of elements. Interest in these methods is due to the relative simplicity of the analysis, the ability to provide the required sensitivity and accuracy of detection of chemical elements. The main objective of the research work is to demonstrate the potential of these techniques for controlling the quality and safety of food products and for research of trace elements' biokinetics with achieving the required accuracy (no worse than 15%) and sensitivity (below the permissible concentrations of harmful substances) and to prepare them for the practical application. Both methods complement each other in terms of expanding the list of detected chemical elements and choosing the best option in the analysis depending on the type of the test sample and readiness of technical means. In addition to the analysis of NAAMs and XRFA capabilities two different but partly connected research options were performed using NAAMs: 1) control of food quality and safety; 2) research of biokinetics of nanoparticles (NPs), incoming with food and water into laboratory animals with special attention to overcoming biological barriers. One of the important result is the demonstration of overcoming the blood/brain barrier by silver NPs when they are ingested into the animals with food or water, and possibility of their accumulation in brains with extremely low excretion (≈6% per month).

A distance correction method for improving the accuracy of particle coal online X-ray fluorescence analysis – Part 2: Method and experimental investigation

The distance from X-Ray Fluorescence (XRF) spectrometer to sample surface always changes with the different coal's particle sizes, resulting in the inaccuracy of online XRF measurement. To improve the accuracy of particle coal online XRF analysis, a distance correction method was established elaborated by iteration, which was based on the relationship between the XRF intensity and the distance. In order to verify the effectiveness of this method, five different particle size coal samples with same components have been measured by the online XRF analyzer directly above the conveyor belt, in the meanwhile, the distances between XRF spectrometer and samples’ surface were obtained by a laser rangefinder. The results showed that the average distances are decreased with decreasing the particle size. By comparing the results of before and after applying the distance correction method, we demonstrated that the measurement accuracy of online XRF analysis for particle coal can be significantly increased. The distance correction method can be used for the development of online XRF analysis techniques applicable for real-time industrial processes.

A distance correction method for improving the accuracy of particle coal online X-ray fluorescence analysis - Part 1: Theoretical dependence of XRF intensity on the distance

During online X-ray fluorescence (XRF) measurement, the distance from XRF spectrometer to the sample surface always changes due to the rough surface textures of pulverized coal, resulting in changes in the X-ray fluorescent intensity and inaccuracy of online XRF measurement. To solve the impact of the sample's rough surface textures on the measurement accuracy, the theory and validity details of the dependence of XRF intensity on the distance as well as the comparison of the formula derivation and experimental verification were elaborated in the present research. A typical XRF calculation model has been built for theoretical derivation. The expression of the relationship between the XRF intensity and the distance from XRF spectrometer to sample surface was derived, where the variation of the distance influenced five physical phenomena: (1) absorption of X-rays by the air, (2) irradiated surface area of the samples, (3) changes in exit angle, (4) changes in solid angle and (5) absorption of X-ray fluorescence by the air. The intensities of the Fe Kα spectral lines in iron were calculated and agreed with the experiments very well, indicating that the expression of the dependence was accurate. The dependence of X-ray fluorescence intensity on the distance is the theoretical basis of the distance correction method to improve the accuracy of online XRF analysis techniques in industrial processes.

The use of the ratios of intensities of spectral lines for X-ray fluorescence analysis of metal alloys and oxide materials

An X-ray fluorescence analysis technique is proposed, which is based on using ratios of intensities of spectral lines. The technique includes performing calculations for evaluation of calibration equations, which allows using few reference samples or carrying out standardless analysis, if necessary. That parameters of the calibration equations depend linearly on concentrations of disturbing elements allows one to simplify taking their influence into account. To apply the developed technique to analysis of samples containing a significant amount of undetectable light elements, a use of a dependence of intensity ratio of the characteristic radiation of the X-ray tube’s anode, coherently and incoherently scattered by a sample, on a total content of undetectable elements is proposed. The technique’s adequacy is demonstrated by analysis of standard steel samples, metal cuttings and iron-ore materials.

Characterization of the 8-stage Rotating Drum Impactor under low concentration conditions

The Rotating Drum Impactor (RDI) is designed to collect samples of airborne particulate matter that are resolved by aerodynamic particle diameter as a function of time. The purpose of this study is to characterize the accuracy and precision of measurements for particulate matter less than 2.5μm (PM2.5) from the latest generation of the RDI sampler for use in relatively low concentration environments. Nominal RDI size cuts were used to interpret the results; a laboratory calibration of the RDI was not undertaken. Airborne particulate matter was collected on the campus of the University of California at Davis during the winter and summer of 2013. Two RDI samplers operating with 1h resolution, two IMPROVE samplers operating 21h per day, and one MOUDI sampler operating 42h every two days were deployed for both seasons to enable a comparison of co-located measurements. The RDI samples were scanned using synchrotron X-rays from the Advanced Light Source (ALS), Lawrence National Berkeley Laboratory, to obtain X-ray Fluorescence (XRF) spectra. IMPROVE and MOUDI samples were analyzed using Panalytical XRF instruments using the IMPROVE protocol, then analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) using an Agilent 7500i. Repeated measurements from the same samplers and analytical techniques were compared to elucidate precision; inter-comparisons between measurements made with different sampler and analytical technique combinations were used to indirectly evaluate accuracy.The IMPROVE XRF analysis technique gave similar repeated measurements for 78% of the elements present above stated Minimum Detection Limits (MDLs) in winter and 42% of elements above MDL in summer. The MOUDI XRF analysis technique gave similar repeated measurements for 33% and 37% of the elements above stated MDLs in winter and summer, respectively. The MOUDI, ICP-MS analysis technique was the most repeatable method tested, yielding similar repeated measurements for 62% and 91% of elements above stated MDLs in winter and summer, respectively. The RDI, XRF analysis technique was the least repeatable method tested, yielding similar repeated measurements for 35–40% and 5–20% of elements above stated MDLs in winter and summer, respectively.PM2.5 measurements from IMPROVE samplers were in better agreement with integrated size-resolved measurements made by MOUDI samplers than RDI samplers in the summer season, however with higher concentrations in the winter season both instruments performed with similar accuracy when using the XRF analysis method. MOUDI samples analyzed by ICP-MS had the best agreement overall with IMPROVE samples analyzed by ICP-MS. These results suggest that MDLs should be reassessed for all methods and a longer collection time should be considered under low concentration conditions.

High accuracy experimental determination of copper and zinc mass attenuation coefficients in the 100 eV to 30 keV photon energy range

The knowledge of atomic fundamental parameters such as mass attenuation coefficients with low uncertainties, is of decisive importance in elemental quantification using x-ray fluorescence analysis techniques. Several databases are accessible and frequently used within a large community of users. These compilations are most often in good agreement for photon energies in the hard x-ray ranges. However, they significantly differ for low photon energies and around the absorption edges of any element. In a joint cooperation of the metrology institutes of France and Germany, mass attenuation coefficients of copper and zinc were determined experimentally in the photon energy range from 100 eV to 30 keV by independent approaches using monochromatized synchrotron radiation at SOLEIL (France) and BESSY II (Germany), respectively. The application of high-accuracy experimental techniques resulted in mass attenuation coefficient datasets determined with low uncertainties that are directly compared to existing databases. The novel datasets are expected to enhance the reliability of mass attenuation coefficients.

Electrochemical behavior of olivine-type LiMnPO4-based material in a mild aqueous electrolyte

Olivine-type pristine LiMnPO4 and nickel-substituted LiNi0.05Mn0.95PO4 electrode materials were synthesized via a sol–gel route, and characterized by X-ray diffraction (XRD), transmission electron microscopy, and X-ray fluorescence analysis techniques. Their electrochemical properties in 2 M Li2SO4 aqueous solution were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge methods. Furthermore, X-ray absorption near edge structure analysis and XRD technique were employed to study the structural change of the pristine LiMnPO4 during the first charge/discharge cycle and the first-stage repeated charge/discharge activation cycles (increase in discharge capacity with increasing cycle number). The LiMnPO4-based electrodes were found to undergo a first-stage activation process with gradual increase in discharge capacity prior to capacity degradation in the experimental condition. Partial nickel substitution for manganese in LiMnPO4 can enhance the charge transfer reaction kinetics, and thereby increase the specific capacity of the LiMnPO4-based electrode.

Mitigation of DEF in concrete: morphology and composition studies

Experiments were performed to study the effects of select chemicals on the mitigation of delayed ettringite formation in Portland cement concrete (PCC) specimens. Specimens were prepared, conditioned and chemically treated with crystal growth inhibitors or waterproofing agents. They were then cured and physical properties were evaluated as a function of curing time. Reaction products were evaluated using scanning electron microscopy and energy dispersive X-ray fluorescence analysis techniques. While the chemicals did not mitigate delayed ettringite formation, the systems did yield large amounts of secondary ettringite of various morphologies. The lack of mitigation of delayed ettringite formation may be attributable to an overabundance of ettringite resulting from intensive conditioning protocol and/or too low a dosage of crystal growth inhibitor or waterproofing agent. Characterisation of the systems revealed some trends in morphological development, for example the samples cured for long times had a preponderance of lamella and laths involved. These and other morphologies observed were consistent with the literature, especially those studies based on scanning electron microscope evaluations of fracture surfaces. Chemical compositions, determined by energy dispersive X-ray fluorescence analysis, regardless of treatment or curing time, were generally quite similar, showing reasonable ratios of calcium: sulfur: aluminium. While delayed ettringite formation mitigation was not achieved, the results demonstrate the usefulness of scanning electron microscopy/energy dispersive X-ray fluorescence analysis examination of fracture surfaces for the evaluation of morphological and chemical features in concrete durability studies.

Influence of the distance between a spectrometer and sample on the intensity of X-ray fluorescence

Expressions for calculating the extreme point coordinates of focal spots of X-ray tubes and a detector’s sensitive area are found. These coordinates are used in calculations of the sample area. The dependence of the X-ray fluorescence intensity on the distance between a spectrometer and an analyzed sample is studied experimentally. The intensities of the FeKα spectral lines in iron-containing materials are calculated at different geometric parameters of a spectrometer. It is found that the distance between a sample and detector at which the maximum of the measured intensity is observed depends on the size and position of the detector and X-ray tube collimators, as well as on the relative position of the X-ray tube and detector. Recommendations on how to achieve the maximum intensity of X-ray fluorescence are proposed. The results of the present work can be used for the development of X-ray fluorescence analysis techniques applicable for free-flowing materials directly in technological processes.

Specific features of X-ray fluorescence analysis techniques using capillary lenses and synchrotron radiation

This paper discusses the features of an application of two versions of X-ray fluorescence analysis (XRF), commonly used at present, namely XRF using synchrotron radiation to excite the fluorescence in the sample investigated (SRXRF), and XRF using capillary X-ray optics. The operational characteristics of different models of micro-XRF spectrometers are considered. The general differences between conventional XRF and SRXRF and their influence on the choice of the analytical procedure are also presented. Examples of the typical errors resulting from the use of some classical analytical procedures in several applications are illustrated.

Research Note: Energy dispersive x-ray fluorescence analysis technique for geological, biological and environmental samples.

Energy Dispersive X-Ray fluorescence (EDXRF) technique for the analysis of geological, biological and environmental samples is described. The technique has been applied in the analysis of 10 (geological, biological, environmental) standard reference materials. The accuracy and precision of the technique were attested to by the good agreement between our measured results and the certified values of these standards. The measured and the certified values were generally within 5% of each other except for a few cases that were within 15% of each other for the geological samples. Ife Journal of Science Vol.6(1) 2004: 88-90