Combined X-ray Fluorescence Research Articles

Quantitative surface characterization of silicon spheres by combined XRF and XPS analysis for the determination of the Avogadro constant

For the quantitative surface characterization of a monocrystalline silicon sphere, PTB has constructed and put into operation an analytical instrument, which combines x-ray fluorescence and x-ray photoelectron spectroscopy techniques. The main objective of this novel instrument is the characterization of the oxide layer and unintentional contaminations, e.g. from hydrocarbons. It is equipped with a ball manipulator allowing measurements at each point on the surface of ball-shaped samples with a diameter of about 93.7 mm. Monocrystalline silicon spheres with this diameter allow a realization of the SI base unit of mass.

Combined use of X-ray fluorescence microscopy, phase contrast imaging for high resolution quantitative iron mapping in inflamed cells

X-ray fluorescence microscopy (XRFM) is a powerful technique to detect and localize elements in cells. To derive information useful for biology and medicine, it is essential not only to localize, but also to map quantitatively the element concentration. Here we applied quantitative XRFM to iron in phagocytic cells. Iron, a primary component of living cells, can become toxic when present in excess. In human fluids, free iron is maintained at 10-18 M concentration thanks to iron binding proteins as lactoferrin (Lf). The iron homeostasis, involving the physiological ratio of iron between tissues/secretions and blood, is strictly regulated by ferroportin, the sole protein able to export iron from cells to blood. Inflammatory processes induced by lipopolysaccharide (LPS) or bacterial pathoge inhibit ferroportin synthesis in epithelial and phagocytic cells thus hindering iron export, increasing intracellular iron and bacterial multiplication. In this respect, Lf is emerging as an important regulator of both iron and inflammatory homeostasis. Here we studied phagocytic cells inflamed by bacterial LPS and untreated or treated with milk derived bovine Lf. Quantitative mapping of iron concentration and mass fraction at high spatial resolution is obtained combining X-ray fluorescence microscopy, atomic force microscopy and synchrotron phase contrast imaging.

Joint reconstruction of x-ray fluorescence and transmission tomography.

X-ray fluorescence tomography is based on the detection of fluorescence x-ray photons produced following x-ray absorption while a specimen is rotated; it provides information on the 3D distribution of selected elements within a sample. One limitation in the quality of sample recovery is the separation of elemental signals due to the finite energy resolution of the detector. Another limitation is the effect of self-absorption, which can lead to inaccurate results with dense samples. To recover a higher quality elemental map, we combine x-ray fluorescence detection with a second data modality: conventional x-ray transmission tomography using absorption. By using these combined signals in a nonlinear optimization-based approach, we demonstrate the benefit of our algorithm on real experimental data and obtain an improved quantitative reconstruction of the spatial distribution of dominant elements in the sample. Compared with single-modality inversion based on x-ray fluorescence alone, this joint inversion approach reduces ill-posedness and should result in improved elemental quantification and better correction of self-absorption.

Feasibility study of Compton cameras for x-ray fluorescence computed tomography with humans

X-ray fluorescence imaging is a promising imaging technique able to depict the spatial distributions of low amounts of molecular agents in vivo. Currently, the translation of the technique to preclinical and clinical applications is hindered by long scanning times as objects are scanned with flux-limited narrow pencil beams. The study presents a novel imaging approach combining x-ray fluorescence imaging with Compton imaging. Compton cameras leverage the imaging performance of XFCT and abolish the need for pencil beam excitation. The study examines the potential of this new imaging approach on the base of Monte-Carlo simulations. In the work, it is first presented that the particular option of slice/fan-beam x-ray excitation has advantages in image reconstruction in regard of processing time and image quality compared to traditional volumetric Compton imaging. In a second experiment, the feasibility of the approach for clinical applications with tracer agents made from gold nano-particles is examined in a simulated lung scan scenario. The high energy of characteristic x-ray photons from gold is advantageous for deep tissue penetration and has lower angular blurring in the Compton camera. It is found that Doppler broadening in the first detector stage of the Compton camera adds the largest contribution on the angular blurring; physically limiting the spatial resolution. Following the analysis of the results from the spatial resolution test, resolutions in the order of one centimeter are achievable with the approach in the center of the lung. The concept of Compton imaging allows one to distinguish to some extent between scattered photons and x-ray fluorescent photons based on their difference in emission position. The results predict that molecular sensitivities down to 240 pM l−1 for 5 mm diameter lesions at 15 mGy for 50 nm diameter gold nano-particles are achievable. A 45-fold speed up time for data acquisition compared to traditional pencil beam XFCT could be achieved for lung imaging at the cost of a small sensitivity decrease.

Combined micro-XRF and TXRF methodology for quantitative elemental imaging of tissue samples

Local differences in structural properties of biological specimens pose a major limitation to quantitative X-ray fluorescence imaging. This is because both the various tissue compartments of different density and variation in the sample thickness upon frequently used freeze-drying come up with the different values of the sample mass per unit area to be taken into account. Even though several solutions to tackle this problem based on the home-made standards for quantification in terms of thickness- and density-independent elemental mass fractions have been proposed, this issue is not addressed enough due to the samples’ heterogeneity. In our recent study, we propose a calculation scheme based on combined external-standard micro X-ray fluorescence (micro-XRF) imaging and internal-standard total reflection X-ray fluorescence (TXRF) analysis to determine the corrected elemental mass fraction distributions in commonly analysed rat tissues: kidney, liver and spleen. The results of TXRF analysis of digested large tissue sections together with the mean values of elemental masses per unit area obtained with micro-XRF were employed to determine the average masses per unit area of the samples. The correction for variation of the tissue thickness and density was done through with the use of Compton intensities. Importantly, by its versatility, our novel approach can be used to produce elemental contrast in a variety of biological specimens where local variations in either the sample density or thickness are no longer the issue.

X-ray fluorescence spectroscopy and Monte Carlo characterization of a unique nuragic artifact (Sardinia, Italy)

The chemical composition of a unique bronze artifact known as the “Cesta” (“Basket”) belonging to the ancient Nuragic civilization of the Island of Sardinia, Italy has been analyzed by combining X-ray Fluorescence Spectroscopy (XRF) with Monte Carlo simulations using the XRMC code. The “Cesta” had been discovered probably in the XVIII century with the first graphic representation reported around 1761. In a later draft (dated 1764), the basket has been depicted as being carried upside-down on the shoulder of a large bronze warrior Barthélemy (1761), Pinza (1901), Winckelmann (1776) . The two pictorial representations differed only by the presence of handles in the most recent one. XRF measurements revealed that the handles of the object are composed by brass while the other parts are composed by bronze suggesting the handles as being a later addition to the original object. The artifact is covered at its surface by a fairly thick corrosion patina. In order to determine the bronze bulk composition without the need for removing the outer patina, the artifact has been modeled as a two layer object in Monte Carlo simulations.

Geochemical study of beveled rim bowls from the Middle Syrian Euphrates sites

Among the pottery of the Middle Uruk period (or Late Chalcolithic 4) in Syria-Mesopotamia (3800–3450BCE), it is perhaps the beveled rim bowls (BRBs) which are the most usually interpreted as a “reference pottery” of this period. The BRB is a type of very basic, hand and mass-made bowl characterised by the standardisation of its shape. Despite the thousands of BRBs found in the sites linked to the expansion of Southern Uruk culture, their function continues to be debated. It is also unclear if the production and distribution of BRBs was performed by the large centres controlled by an institution (regional or state) or not. We have studied BRBs from two nearby sites of the Southern Middle Euphrates in Syria (Tell Humeida and Tell Ramadi) using mineralogical (petrographic observations and X-ray diffraction) and chemical analyses combining X-ray Fluorescence, Inductively Coupled Plasma-Mass Spectrometry and Instrumental Neutron Activation Analysis to assess if BRBs were produced in a single centre in the Syrian Euphrates. We have compared results considering major, minor and trace elements, analytical methods and sites as a first step for full comparison of BRBs from sites of the whole of Mesopotamia. Results show a very good fit among samples from the Syrian Southern Middle Euphrates, and some points are considered on the use of specific elements to assess provenance and monitor trade.

Scientific face of the artwork: Investigation of the pigments and plasters of the wall paints of some ottoman mosques by FTIR and EDXRF techniques

The characterization of the pigments and plasters of the wall paints of some Ottoman Mosques have been performed using combined Energy Dispersive X-Ray Fluorescence (EDXRF) and Fourier Transform Infrared (FTIR) spectrometry (both in reflection and transmission modes) techniques. The colored wall paints were obtained from Fatih Mosques of Istanbul-Turkey and Pristina-Kosovo, and Suleymaniye Mosque of Istanbul-Turkey, during the restoration periods of the mosques. The investigations show that the plaster used on the walls has mixed gypsum-lime binders. The pigments identified in wall paints are: cinnabar (HgS), lead red (Pb 3 O 4 ) and hematite (α-Fe 2 O 3 ) in red colors, ultramarine blue (Na 8-10 Al 6 Si 6 O 24 S 2-4 ) as blue and green earth as green colors. The results provide a basis for future restoration of the wall paints. Keywords: Pigments, Plasters, FTIR spectroscopy, EDXRF

Scientific face of the artwork: Investigation of the pigments and plasters of the wall paints of some ottoman mosques by FTIR and EDXRF techniques

The characterization of the pigments and plasters of the wall paints of some Ottoman Mosques have been performed using combined Energy Dispersive X-Ray Fluorescence (EDXRF) and Fourier Transform Infrared (FTIR) spectrometry (both in reflection and transmission modes) techniques. The colored wall paints were obtained from Fatih Mosques of Istanbul-Turkey and Pristina-Kosovo, and Suleymaniye Mosque of Istanbul-Turkey, during the restoration periods of the mosques. The investigations show that the plaster used on the walls has mixed gypsum-lime binders. The pigments identified in wall paints are: cinnabar (HgS), lead red (Pb3O4) and hematite (α-Fe2O3) in red colors, ultramarine blue (Na8-10Al6Si6O24S2-4) as blue and green earth as green colors. The results provide a basis for future restoration of the wall paints.Keywords: Pigments, Plasters, FTIR spectroscopy, EDXRF

Scientific face of the artwork: Investigation of the pigments and plasters of the wall paints of some ottoman mosques by FTIR and EDXRF techniques

The characterization of the pigments and plasters of the wall paints of some Ottoman Mosques have been performed using combined Energy Dispersive X-Ray Fluorescence (EDXRF) and Fourier Transform Infrared (FTIR) spectrometry (both in reflection and transmission modes) techniques. The colored wall paints were obtained from Fatih Mosques of Istanbul-Turkey and Pristina-Kosovo, and Suleymaniye Mosque of Istanbul-Turkey, during the restoration periods of the mosques. The investigations show that the plaster used on the walls has mixed gypsum-lime binders. The pigments identified in wall paints are: cinnabar (HgS), lead red (Pb3O4) and hematite (α-Fe2O3) in red colors, ultramarine blue (Na8-10Al6Si6O24S2-4) as blue and green earth as green colors. The results provide a basis for future restoration of the wall paints.Keywords: Pigments, Plasters, FTIR spectroscopy, EDXRF

Mid-Infrared and Total X-Ray Fluorescence Spectroscopy Complementarity for Assessment of Soil Properties

Diffuse reflectance Fourier transformed mid-infrared (DRIFT-MIR) spectroscopy can predict many soil properties but extractable nutrients are often predicted poorly. This paper tested the combined DRIFT-MIR and total X-ray fluorescence (TXRF) spectroscopy analysis for prediction of soil properties related to soil fertility. A total of 700 soil samples from 44 stratified randomly located 100-km2 sentinel sites distributed across Sub-Saharan Africa (SSA) were analyzed for physicochemical composition using conventional reference methods, and compared with MIR and TXRF spectra using Random Forests (RF) regression algorithm and an internal out-of-bag (OOB) validation. Mid-infrared spectra resulted in good prediction models (R2 > 0.80) for organic C and total N, Mehlich-3 Ca and Al, and pH. Moderately predicted (R2 > 0.60) were extractable Mg, P sorption index, sand, silt, and clay. Models were less satisfactory (R2 < 0.60) for Mehlich-3 extractable K, Mn, Fe, Cu, B, Zn, P, S, and Na, exchangeable acidity and electrical conductivity (Ecd). Inclusion of total element concentration data from TXRF analysis in the MIR RF models significantly reduced root mean square error of prediction by 70% for Ecd, 66% for Mehlich-3 Na, 61% for Mehlich-3 S, and 50% for Mehlich-3 B due to detection by TXRF of some saline soils that were not well predicted by MIR. Overall, both methods predicted soil properties that relate to nutrient buffering capacity, including some exchangeable bases, pH, P sorption capacity, clay content, and organic matter content, and fingerprint basic soil mineralogy. Thus, further research should test whether MIR and TXRF fingerprinting could better predict soil nutrient supply capacity, as determined by crop nutrient uptake potential, than conventional soil P, K and micronutrient tests.

Gold Deposition at a Free-Standing Liquid/Liquid Interface: Evidence for the Formation of Au(I) by Microfocus X-ray Spectroscopy (μXRF and μXAFS) and Cyclic Voltammetry

Electrochemical gold nucleation and nanoparticle growth at a liquid/liquid interface were examined in situ by combined X-ray fluorescence (XRF) mapping with a microfocus X-ray beam and X-ray absorption fine structure (XAFS) spectroscopy. Gold deposition was achieved by reduction of [AuCl4]− with tri-p-tolylamine at a water/1,2-dichlorobenzene interface using a windowless liquid/liquid interface system formed from the contact of aqueous and organic phase droplets. The combination of XRF and XAFS, with a spatial resolution of approximately 70 μm, provided chemical speciation information near the interface under gold deposition conditions. Analysis of the X-ray absorption near-edge structure (XANES) reveals evidence for the presence of Au(I) species as a reduction intermediate, concomitant with a buildup of metallic gold at the interface. Cyclic voltammetry indicates the presence of two ion transfer peaks at the liquid/liquid interface, which are assigned to the transfer of [AuCl4]− and [AuCl2]−. Finally ex situ TEM analysis shows that the resultant nanoparticles have an average size between 3 and 4 nm. In line with this particle size, the XAFS indicates bulk-like structure.

Nanocrystalline and stacking-disordered β-cristobalite AlPO4: the now deciphered main constituent of a municipal sewage sludge ash from a full-scale incineration facility

For the first time evidence is provided that a nanocrystalline and stacking-disordered, chemically stabilized β-cristobalite form of AlPO4 occurs in a sewage sludge ash (SSA). This proof is based on a combined X-ray powder diffraction and X-ray fluorescence investigation of an SSA produced at a large-scale fluidized bed incineration facility serving a catching area with a population of 2 million. The structural and chemical characterization was carried out on ‘as received’ SSA samples as well as on solid residues remaining after leaching this SSA in sodium hydroxide solution. Thus, it was ascertained that the observed nanocrystalline and stacking-disordered cristobalite-like component belongs to the aluminum phosphate component of this SSA, rather than to its silicon dioxide component. In addition, a direct proof is presented that the chemically stabilized β-cristobalite form of AlPO4 does crystallize from X-ray amorphous precursors under conditions that mimic the huge heating rate and short retention time (just seconds at T ≈ 850°C), typical for fluidized bed incinerators.

Volcanic iron fertilization of primary productivity at Kerguelen Plateau, Southern Ocean, through the Middle Miocene Climate Transition

ODP Site 747, central Kerguelen Plateau, contains a nearly complete record of the Middle Miocene Climate Transition (MMCT). Its unusually well preserved and rich foraminiferal assemblages have resulted in the MMCT interval at Site 747 becoming a focus of high-resolution paleoclimatic studies that have established this sequence as a Southern Ocean reference. We combine X-ray fluorescence (XRF) elemental counts of Fe, Ti, and Al and concentration-dependent magnetic parameters to trace volcanic ash input to sediments at ODP Hole 747A. We observe systematic variations in Al/Ti and Fe/Ti ratios that are consistent with increased primary productivity at times of increased terrigenous input and, therefore, increased nutrient supply. A spike in terrigenous material, which we interpret as volcanic ash, coincides with major changes in species abundance and stable oxygen and carbon isotopic shifts within the MMCT interval. This correlation suggests that nutrient flux associated with volcanic iron fertilization played a significant role in controlling phytoplankton communities at Site 747. We demonstrate that rapidly obtained XRF and magnetic parameters can provide useful proxies for terrigenous input and, therefore, nutrient fluxes in pelagic marine settings that can help to resolve local versus global drivers of paleoenvironmental and paleoceanographic changes.

Development of a combined portable x-ray fluorescence and Raman spectrometer for in situ analysis.

In this work, we have built a portable X-ray fluorescence (XRF) spectrometer in a planar configuration coupled to a Raman head and a digital optical microscope, for in situ analysis. Several geometries for the XRF apparatus and digital microscope are possible in order to overcome spatial constraints and provide better measurement conditions. With this combined spectrometer, we are now able to perform XRF and Raman measurements in the same point without the need for sample collection, which can be crucial when dealing with cultural heritage objects, as well as forensic analysis. We show the capabilities of the spectrometer by measuring several standard reference materials, as well as other samples usually encountered in cultural heritage, geological, as well as biomedical studies.

Occurrence of brominated flame retardants in black thermo cups and selected kitchen utensils purchased on the European market

In order to screen for the presence of a recycled polymer waste stream from waste electric and electronic equipment (WEEE), a market survey was conducted on black plastic food-contact articles (FCA). An analytical method was applied combining X-ray fluorescence spectrometry (XRF) with thermal desorption gas chromatography coupled with mass spectrometry (thermal desorption GC-MS). Firstly, XRF spectrometry was applied to distinguish bromine-positive samples. Secondly, bromine-positive samples were submitted for identification by thermal desorption GC-MS. Generally, the bromine-positive samples contained mainly technical decabromodiphenyl ether (decaBDE). Newer types of BFRs such as tetrabromobisphenol A (TBBPA), tetrabromobisphenol A bis(2,3-dibromopropyl), ether (TBBPA-BDBPE) and decabromodiphenylethane (DBDPE), replacing the polybrominated diphenyleters (PBDEs) and polybrominated diphenyls (PBBs), were also identified. In none of the tested samples were PBBs or hexabromocyclododecane (HBCD) found. Polymer identification was carried out using Fourier-transformed infrared spectroscopy measurement (FTIR) on all samples. The results indicate that polypropylene–polyethylene copolymers (PP-PE) and mainly styrene-based food-contact materials, such as acrylonitrile-butadiene-styrene (ABS) have the highest risk of containing BFRs.

Evidence of formation of the tridymite form of AlPO4 in some municipal sewage sludge ashes

Evidence is provided that the tridymite component observed in the X-ray diffraction patterns of some sewage sludge ashes (SSAs) should not be interpreted as the tridymite modification of SiO2 but as the tridymite form of AlPO4. This proof is based on a combined X-ray Powder Diffraction (XRD), X-ray fluorescence (XRF) and Mossbauer spectroscopy investigation of two SSAs produced at two fluidized bed incineration facilities, located in different municipalities and operated differently. The structural and chemical characterization was carried out on the ‘as received’ SSA samples as well as on the residues of these two SSAs pretreated by leaching in citric acid. In addition, direct proof is presented that the tridymite form of AlPO4 does crystallize from X-ray amorphous precursors under conditions that mimic the huge heating rate and short retention time (just seconds at T ≈ 850 °C) typical for fluidized bed incinerators.

Combined X-ray fluorescence and absorption computed tomography using a synchrotron beam

X-ray computed tomography (CT) and fluorescence X-ray computed tomography (FXCT) using synchrotron sources are both useful tools in biomedical imaging research. Synchrotron CT (SRCT) in its various forms is considered an important technique for biomedical imaging since the phase coherence of SR beams can be exploited to obtain images with high contrast resolution. Using a synchrotron as the source for FXCT ensures a fluorescence signal that is optimally detectable by exploiting the beam monochromaticity and polarisation. The ability to combine these techniques so that SRCT and FXCT images are collected simultaneously, would bring distinct benefits to certain biomedical experiments. Simultaneous image acquisition would alleviate some of the registration difficulties which comes from collecting separate data, and it would provide increased information about the sample: functional X-ray images from the FXCT, with the morphological information from the SRCT. A method is presented for generating simultaneous SRCT and FXCT images. Proof of principle modelling has been used to show that it is possible to recover a fluorescence image of a point-like source from an SRCT apparatus by suitably modulating the illuminating planar X-ray beam. The projection image can be successfully used for reconstruction by removing the static modulation from the sinogram in the normal flat and dark field processing. Detection of the modulated fluorescence signal using an energy resolving detector allows the position of a fluorescent marker to be obtained using inverse reconstruction techniques. A discussion is made of particular reconstruction methods which might be applied by utilising both the CT and FXCT data.

Iron-Age bronze statuettes in Southern Portugal: combining archaeological data with EDXRF and BSEM + EDS to assess provenance and production technology

A simple, fast, and nondestructive analytical methodology combining X-ray Fluorescence (EDXRF) and Back-scattered Electron Microscopy coupled with Energy Dispersive Spectroscopy (BSEM+EDS) has been applied to characterize the alloy’s composition of ex-votos metal statuettes of unknown provenance and age stored in the Museum of Evora in Southern Portugal, and to compare it with Iron-Age artefacts of similar typology recovered from the well-known Phoenician settlement (7th century BC) of Alcacer do Sal located about 50 km W of Evora. The aim of the study was two-fold: (a) to confirm the age and provenance of the bronzes from the Alcacer settlement; (b) to assess whether the combined archaeometric approach could shed light on the interaction between local (Iberian peninsula) and allochtonous (Phoenician) technological know-how and on how the “Orientalizing” Phoenician influence had been modulated locally in the making of metal artifacts. In this respect, for comparative purposes, selected bronze statuettes displaying “Orientalizing” features of inferred Phoenician origin from the Nuragic collection of the National Archaeological Museum in Cagliari and the G.A. Sanna Museum of Sassari, Sardinia, were also analyzed by EDXRF. Results indicate that all statuettes are made of an alloy of Cu/Sn or Cu/Sn/Pb with variable Sn and Pb content. The presence and content of Pb and of Fe (the latter always >0.05 %) in the alloy suggest a production technology involving the smelting of ferrous minerals and/or the use of reducing firing conditions with locally available Pb intentionally added as fluxing agent. The alloy’s compositional data is consistent with a provenance of the Evora statuettes from the known Phoenician settlement of Alcacer do Sal in Southern Portugal.

Wet sample confinement by superhydrophobic patterned surfaces for combined X-ray fluorescence and X-ray phase contrast imaging

In this work we propose a wet sample handling technique which enables the simultaneous collection of X-ray fluorescence (XRF) spectra and X-ray phase contrast imaging (XPCI) using a few microliters drop confined on a superhydrophobic surface. To this purpose, we fabricated and tested a superhydrophobic patterned surface entailing an hydrophilic region which leads to pinning of the drop, enabling X-ray beam effortless alignment and measuring in liquid phase. Our technique allows to acquire capillary-free XRF spectra, resulting in a significant fluorescence detection gain, which is particularly interesting for light elements. Simultaneous XPCI provides sample geometry assuring a fine control of the experimental conditions and allowing real time monitoring of the drop during measurements. As an additional advantage - after solvent evaporation - the solute is deposited on a precise spot, greatly increasing its concentration allowing further measurements, such as X-ray microanalysis and X-ray diffraction. These results could have potential applications in the study of blood proteins, such as ferritin and low density lipoprotein, which are usually available in very limited quantity.