Synchrotron Radiation Microprobe Research Articles

Evaluation of quantitative synchrotron radiation micro-X-ray fluorescence in rice grain.

Concentrations of nutrients and contaminants in rice grain affect human health, specifically through the localization and chemical form of elements. Methods to spatially quantify the concentration and speciation of elements are needed to protect human health and characterize elemental homeostasis in plants. Here, an evaluation was carried out using quantitative synchrotron radiation microprobe X-ray fluorescence (SR-µXRF) imaging by comparing average rice grain concentrations of As, Cu, K, Mn, P, S and Zn measured with rice grain concentrations from acid digestion and ICP-MS analysis for 50 grain samples. Better agreement was found between the two methods for high-Z elements. Regression fits between the two methods allowed quantitative concentration maps of the measured elements. These maps revealed that most elements were concentrated in the bran, although S and Zn permeated into the endosperm. Arsenic was highest in the ovular vascular trace (OVT), with concentrations approaching 100 mg kg-1 in the OVT of a grain from a rice plant grown in As-contaminated soil. Quantitative SR-µXRF is a useful approach for comparison across multiple studies but requires careful consideration of sample preparation and beamline characteristics.

Br diffusion in phonolitic melts: Comparison with fluorine and chlorine diffusion

Abstract Bromine diffusion was measured in two natural phonolitic melts: (1) a K2O-rich (~10 wt%) one synthesized from the white pumice phase of the 79 AD eruption of Vesuvius (Italy), and (2) a Na2O-rich (~10 wt%) one corresponding to the most differentiated melt of the 12 000 BC eruption of the Laacher See (Germany). Experiments were performed at 0.5 and 1.0 GPa, 1250 to 1450 °C, at anhydrous and hydrous (2.65 ± 0.35 wt% of dissolved water) conditions. Experiments conducted with the diffusion-couple technique in the piston cylinder were performed with only bromine diffusing and with the simultaneous diffusion of a halogen mixture (F, Cl, Br) to evaluate the interactions between the halogens during diffusion. The diffusion profiles of Br were measured by X-ray fluorescence using synchrotron radiation microprobe (SYXRF), ID18F, at the European Synchrotron Radiation Facility (ESRF, France). Bromine diffusion displays Arrhenian behavior under anhydrous conditions that is similar when it diffuses alone and when it diffuses with F and Cl. The Br diffusion coefficients range between 2 × 10–12 m2/s at 1250 °C and 1.5 × 10–11 m2/s at 1450 °C for the Na-rich melt and between 3 × 10–12 m2/s at 1250 °C and 2.5 × 10–11 m2/s at 1450 °C for the K-rich melt, at 1.0 GPa. Although Br mobility is independent of F and Cl in anhydrous phonolitic melts, its behavior may be dependent on the dominant alkali in the melt, as previously observed for Cl, but not F. For hydrous experiments, although the data are scattered, the Br diffusivity increases slightly with water and the Na/K ratio seems to influence Br diffusivity. Similarly to noble gases, halogen diffusivity at a given temperature in the phonolitic melts appears related to the ionic porosity of the silicate structure. Compared to basaltic melt, Br diffusivities are approximately one order of magnitude lower in the Na-phonolite melt, because of the difference of the pre-exponential factor. Br mobility appears to be decoupled from melt viscosity, considering the results here.

New insights on the biomineralisation process developing in human lungs around inhaled asbestos fibres

Once penetrated into the lungs of exposed people, asbestos induces an in vivo biomineralisation process that leads to the formation of a ferruginous coating embedding the fibres. The ensemble of the fibre and the coating is referred to as asbestos body and is believed to be responsible for the high toxicological outcome of asbestos. Lung tissue of two individuals subjected to prolonged occupational exposure to crocidolite asbestos was investigated using synchrotron radiation micro-probe tools. The distribution of K and of elements heavier than Fe (Zn, Cu, As, and Ba) in the asbestos bodies was observed for the first time. Elemental quantification, also reported for the first time, confirmed that the coating is highly enriched in Fe (~20% w/w), and x-ray absorption spectroscopy indicated that Fe is in the 3+ oxidation state and that it is present in the form of ferritin or hemosiderin. Comparison of the results obtained studying the asbestos bodies upon removing the biological tissue by chemical digestion and those embedded in histological sections, allowed unambiguously distinguishing the composition of the asbestos bodies, and understanding to what extent the digestion procedure altered their chemical composition. A speculative model is proposed to explain the observed distribution of Fe.

A synchrotron radiation micro-X-ray absorption near edge structure study of sulfur speciation in human brain tumors—a methodological approach

Sulfur stands out among non-metallic elements essential to life. In biological systems sulfur exists in various oxidation states, but the most significant role in biochemical processes is played by sulfane sulfur. In this work sulfur speciation in brain tumors was studied using X-ray absorption near edge structure spectroscopy. The comparison of full XANES spectra measured inside the tumor cell, outside the cell and on its periphery with the XANES profiles of reference materials containing sulfur compounds shows that in all the examined tissue sites, sulfur is in the 2− oxidation state. However, special emphasis is placed on the experimental and methodological aspects of two-dimensional imaging of chemical forms of sulfur in tissue sections. It was found that after changing the photon energy of the exciting radiation beam, not only did a permanent shift of its position in the XY plane occur, but also a change in the beam incidence angle on the sample. Therefore procedures to eliminate these effects in imaging the distribution of chemical forms of sulfur, using a synchrotron radiation microprobe, are also shown. The results allowed for the identification of the presence of sulfur in 2−, 4+ and 6+ oxidation states in various tissue structures.

Bioimaging of cells and tissues using accelerator-based sources

A variety of techniques exist that provide chemical information in the form of a spatially resolved image: electron microprobe analysis, nuclear microprobe analysis, synchrotron radiation microprobe analysis, secondary ion mass spectrometry, and confocal fluorescence microscopy. Linear (LINAC) and circular (synchrotrons) particle accelerators have been constructed worldwide to provide to the scientific community unprecedented analytical performances. Now, these facilities match at least one of the three analytical features required for the biological field: (1) a sufficient spatial resolution for single cell (< 1 mum) or tissue (<1 mm) analyses, (2) a temporal resolution to follow molecular dynamics, and (3) a sensitivity in the micromolar to nanomolar range, thus allowing true investigations on biological dynamics. Third-generation synchrotrons now offer the opportunity of bioanalytical measurements at nanometer resolutions with incredible sensitivity. Linear accelerators are more specialized in their physical features but may exceed synchrotron performances. All these techniques have become irreplaceable tools for developing knowledge in biology. This review highlights the pros and cons of the most popular techniques that have been implemented on accelerator-based sources to address analytical issues on biological specimens.

X-ray absorption of Zn1−xCoxO thin films: A local structure study

In this study, the application of synchrotron radiation microprobe to the analysis of Co incorporation in Zn1−xCoxO is reported. From the Co and Zn fluorescence line intensity ratio, the Co concentrations were deduced. A combination of fluorescence mapping with x-ray absorption spectroscopic techniques made possible to examine not only the uniform elemental distribution but also the short range structural order with the Co content. In Zn1−xCoxO films grown by pulsed laser depositions the Co atoms are in tetrahedral site configuration, corresponding to a substitutional site in wurtzite structure. Within the experimental accuracy, no significant bond length deviation from the pure ZnO structure was observed in the considered compositional range.

Micro-x-ray absorption near-edge structure imaging for detecting metallic Mn in GaN

In this study, we report the application of a synchrotron radiation microprobe to the analysis of Mn valencies in GaN. X-ray absorption near-edge structure (XANES) images taken around MnK-edge in fluorescence detection mode reveal the concentration of oxidation states of Mn centers. By fitting the XANES curve for each point of the image, the distributions of the Mn0, Mn2+, and Mn3+ oxidation states are obtained. At low Mn concentrations, there is a homogeneous mixture of Mn2+ and Mn3+ centers, while at high Mn content strong spatial-dependent Mn0 and Mn2+ distributions characterize the XANES maps. In a supplementary way with respect to Mn2+, the Mn0 pattern suggests the presence of specific cluster-like features, indicating surface segregation of metallic Mn centers.

Chemical elements distribution in cells

Analysing, imaging and understanding the cellular chemistry, from macromolecules to monoatomic elements, is probably a major challenge for the scientific community after the conclusion of the genome project. In order to probe the distribution of elements in cells, especially the so-called inorganic elements, it is necessary to apply microanalytical techniques with sub-micrometer resolution and high chemical sensitivity. This paper presents the current status of chemical element imaging inside cells, and a comparison of the different analytical techniques available: nuclear microprobe, electron microprobe and electron energy loss spectroscopy, synchrotron radiation microprobe, secondary ion mass spectrometry and fluorescence microscopy methods. Examples of intracellular chemical elements distributions relevant to cancer pharmacology, medical imaging, metal carcinogenesis and neuropathology studies obtained by nuclear microprobe and other microanalytical techniques are presented.

Mn-rich clusters in GaN: Hexagonal or cubic symmetry?

In this study, we report the application of synchrotron radiation microprobe to the analysis of Mn-rich clusters in GaN. From the Mn and Ga fluorescence line intensity ratio, an average Mn concentration of 11% was deduced. A combination of fluorescence mapping with spectroscopic techniques enabled us to examine not only the cluster elemental nature but also their crystallographic orientation on the submicron scale. The strong polarization-dependent x-ray absorption near-edge structure features showed the preservation of the hexagonal symmetry in both cluster-free and Mn-rich regions. However, from the x-ray absorption data taken inside the clusters, a preferential disorder was observed in the direction parallel to the crystal growth rather than perpendicular to it.

Determination of the alloying content in the matrix of Zr alloys using synchrotron radiation microprobe X-ray fluorescence

The alloying element content in the α-Zr matrix of Zr alloys was studied using synchrotron radiation microprobe X-ray fluorescence, coupled with Monte Carlo simulation of the fluorescence process for quantification of the concentrations. The agreement between the measured values and the bulk concentrations of the alloy standards, as measured by the overall fit of the full fluorescence spectrum, was excellent. We measured the concentration of insoluble alloying elements in the matrix of Zircaloy-4 previously annealed to 705 °C for 125 h (corresponding to a cumulative annealing parameter (CAP) of 2.1 × 10 −16 h, CAP=∑ i t i exp(− Q/ RT i ) where t i is the time (hours) spent at temperature T i (K) and Q/R=40 000 K) and in the matrix of a ZrSnNbFe alloy with a composition similar to ZIRLO TM, but annealed at 710 °C for 92 h. The matrix concentrations of alloying elements were found to be, Fe=290 wt. ppm, Cr=270 wt. ppm in Zircaloy-4 and Fe=250 wt. ppm in the ZrSnNbFe alloy. These results are discussed in light of other experimental determinations of alloying element concentrations in the literature.

QUANTITATIVE ANALYSIS OF BIOLOGICAL SAMPLES USING SYNCHROTRON RADIATION MICROPROBE

A quantitative analysis method of the trace elements in biological specimens using the synchrotron radiation microprobe is described. The synchrotron radiation X-ray fluorescence microprobe system is calibrated by the standard sample specially prepared for the microprobe analysis. The mass thickness of each measured point is determined by measuring Compton scattering intensity in 17–20 keV from the sample. In this way, concentration of the trace elements in samples can be measured correctly. The measured values of the biological standard reference material NBS-SRM-1577a are in good agreement with the certified values. The longitudinal concentration variations of some trace element in a single hair of pregnant women have been measured by this method

SYNCHROTRON RADIATION X-RAY FLUORESCENCE ANALYSIS OF ELEMENTS IN HUMAN GASTRIC CANCER

Synchrotron radiation microprobe XRF analysis has been used in the multielements analysis of human gastric cancer tissues. Elements of P, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, Se, Br and Rb were detected. The relative concentrations of P and K in cancer are higher than in normal tissue, but it is contrary for Cl, Ca, Se and Br.

Synchrotron radiation microprobe analysis of human dental calculi from an archaeological site: A new possible perspective in palaeonutrition studies

AbstractThe X‐ray microprobe at beamline X‐26 of the National Synchrotron Light Source (Brookhaven National Laboratory) has been used to determine minor and trace elements in small fragments of dental calculus. This material was removed from 11 individuals found in the Norman necropolis discovered recently under the church of San Lorenzo di Aversa (Caserta, southern Italy, ca. AD 900–1200). The aim of these experiments is to develop new methods for non‐destructive analysis of organic archaeological materials in studies of palaeonutrition and palaeopathology. These preliminary analyses show little variability in the main trace elements of dietary significance, such as Sr and Zn.

A synchrotron radiation microprobe for X-ray fluorescence and microtomography at ELETTRA. Focusing with bent crystals

An X-ray fluorescence microprobe utilizing the radiation from a bending magnet of ELETTRA, the high-brilliance synchrotron radiation source being built in Trieste, has been proposed. Various focusing monochromators have been considered in order to produce a micron-size beam. Here we use ray-tracing programs to estimate the X-ray fluxes obtainable at ELETTRA with a bent crystal. The performance of the microprobe for trace-element analysis and computed tomography of microscopic biological specimens is also presented.

The synchrotron radiation microprobe at the SRS, daresbury (UK) and its applications

A synchrotron microprobe has been constructed at the Synchrotron Radiation Source at Daresbury (UK). This instrument is capable of analyzing at the ppm level, or, in favourable cases, at the sub-ppm with a lateral resolution of 15 μm. A beam energy of 15 keV was chosen, in order to be able to scan a wide range of analyzable elements. Focusing and monochromation of the white beam was done in a single step with a high precision ellipsoidally curved Si(111) crystal, mounted on an aluminium support. Beam spots of a few tens of microns can be made using an object slit setting of 30 mm horizontally and 5 mm vertically without further collimation. In this spot sufficient flux of 15 keV (quasi-monochromatic) X-rays is available for measuring trace elements at the femtogram level. Measurements on biological materials demonstrated the lower detection limits obtainable with micro-SXRF as compared to micro-techniques using ion-accelerators, especially for the higher Z-elements. Moreover, the much lower energy deposited in the specimen represents a major argument for prefering X-rays to ions for the analysis of radiation sensitive samples. Measurements on a geological reference sample showed better sensitivities for X-rays than protons and electrons for the higher Z-elements.

A synchrotron radiation microprobe for X-ray fluorescence and microtomography at ELETTRA

A synchrotron radiation microscope based on X-ray fluorescence and computed microtomography for advanced applications in biomedicine, environmental sciences, geology and materials science is described. This microscope will utilize the radiation produced by a bending magnet of ELETTRA, the third-generation, high-brilliance synchrotron radiation facility being built in Trieste. Various wide-band-pass mirror systems operating in an energy range between 7 and 17 keV have been designed. For example, multilayer-coated mirrors in the Kirkpatrick-Baez configuration can produce a spatial resolution of 1 μm 2 for a flux in excess of 10 8 photons per second on the sample ( E = 12 keV, E ΔE = 10 ). This X-ray microprobe will allow micrometric mapping of trace and minor elements and computed tomographic imaging with high resolution, opening a new realm of experiments in different fields of science, such as in vivo elemental scanning and microtomography of cultured cells, analysis of single atmospheric particulates, analysis of cosmic debris collected from the stratosphere and antarctic ice, etc. The preliminary design of the beam line and the performance of the microprobe are discussed.

X-ray focussing for synchrotron radiation microprobe analysis at the SRS, Daresbury (UK)

A toroidal bent Si (111) crystal has been made and used to obtain a spot size reduction and therefore an increased flux density of synchrotron radiation for microprobe trace analysis. Measured beam profiles and fluxes are compared with the results of a ray tracing program, used to simulate the experimental situation. It is shown, that the spotsize has been reduced by a factor of 50 horizontally, and by a factor of 11 vertically, which is in good agreement with the calculations. It indicates a good shape accuracy of the doubly bent crystal. The measured photon flux density of 200 photons/(smA μm 2) is shown to be sufficient to detect trace elements of ppm concentration in an organic matrix with a detection volume of the order of 10 μm diameter.