Laboratory X-ray Fluorescence Research Articles

Quantitative Compositional Analyses of Calcareous Rocks for Lime Industry Using LIBS.

Here, the potential of laser-induced breakdown spectroscopy (LIBS) in grading calcareous rocks for the lime industry was investigated. In particular, we developed a system equipped with non-intensified detectors operating in scanning mode, defined a suitable data acquisition protocol, and implemented quantitative data processing using both partial least squares regression (PLS-R) and a multilayer perceptron (MLP) neural network. Tests were carried out on 32 samples collected in various limestone quarries, which were preliminarily analyzed using traditional laboratory X-ray fluorescence (XRF); then, they were divided into two groups for calibration and validation. Particular attention was dedicated to the development of LIBS methodology providing a reliable basis for precise material grading. The congruence of the results achieved demonstrates the capability of the present approach to precisely quantify major and minor geochemical components of calcareous rocks, thus disclosing a concrete application perspective within the lime industry production chain.

Comprehensive mapping and compositional analysis of the Alca obsidian source, Peru

The Alca obsidian source in southern Peru is one of the largest and most geochemically complex sources of volcanic glass in South America. Hunter-gatherers first discovered and used Alca obsidian for stone tools at the end of the Pleistocene. Alca later became one of the three most economically important and widely distributed sources of obsidian in the Central Andean region. Systematic mapping and geochemical characterization efforts spanning 20+ years have revealed an extensive high-elevation source region composed of six geographically and compositionally distinct sub-sources. Here we synthesize research documenting the 2000 km2 spatial extent of the Alca obsidian source, and we present expanded geochemical datasets for six Alca sub-sources (n = 238 geologic samples) obtained using neutron activation analysis (NAA), laboratory x-ray fluorescence (XRF), and portable (p)XRF. Results for Alca and for six other obsidian sources in the Peruvian Andes illustrate the efficacy of these techniques to discriminate Peruvian obsidian sources, including Alca sub-sources. Comprehensive compositional data from the Alca source area, examined against accumulating obsidian artifact datasets from throughout Peru, reveal past human use of various Alca sub-sources. These cases contribute fine-grained behavioral information, made possible by a complex obsidian source with geographically patterned geochemical variation and a >12,000-year sequence of human interaction with this geologic resource.

Monte Carlo Simulation Aided Quantitative Laboratory X-ray Fluorescence Analysis and Its Application in Provenancing Studies for Geo-Archeological Samples.

A laboratory-based X-ray fluorescence (XRF) methodology is presented for standardless quantified analysis based on a monochromatic X-ray spectrometer coupled to Monte Carlo aided quantification. This procedure will be valuable for many scientific fields (e.g. archaeology, geology, etc.) where the unique nature of the investigated samples calls for the application of non-destructive techniques. To illustrate the value of the methodology, a case study is presented where flint artefacts from the Scheldt basin are analyzed in an attempt to provenance them. So far, little geochemical research has been done in this area. Our results contribute to the creation of a database that will help assign lithic artefacts to specific geological outcrops and will aid further research in this field.

Development and validation of in-situ and laboratory X-ray fluorescence (XRF) spectroscopy methods for moss biomonitoring of metal pollution

Metals are among the pollutants of highest concern in urban areas due to their persistence, bioavailability and toxicity. High concentrations of metals threaten aquatic ecosystem functioning and biodiversity, as well as human health. High-resolution estimates of pollutant sources are required to mitigate exposure to toxic compounds by identifying the specific locations and associated site characteristics where the deposition of metals is greatest. Mosses have been widely used as low-cost biological monitors of metal pollution for decades, because they readily accumulate pollutants over time, reflecting long term pollution levels. However, spectroscopic techniques to determine the concentration of metal pollutants in moss samples still require expensive instrumentation and involve time consuming sample preparation protocols with heavy use of reagents. Here we present protocols to perform in-situ and laboratory X-ray fluorescence (XRF) spectroscopy of epiphytic moss as rapid, low-cost, and accurate alternatives to conventional metal pollution biomonitoring. We also report on a preliminary validation of the measurements using mass fractions determined by inductively coupled plasma atomic emission spectroscopy (ICP-OES) as reference.•XRF measurements are taken from moss directly on tree trunks in less than five minutes.•Grinding and pelletizing of moss enables definitive quantitation (R2>0.90) of metals through portable XRF.

Integrating Multi-Scalar Sampling Strategies for Archaeological Sediment Chemistry

ABSTRACT Archaeological sediment chemistry is a method for using the distribution of chemical elements across a site or landscape to elucidate site boundaries, site structures, and use of space. Archaeologists have sought to implement it at a number of scales, from the analysis of single excavated features to site prospection in regional survey. This article presents a model for an ongoing, multi-scalar collection strategy that builds on previous global work in sediment chemistry. Analyzed data derive from the Bronze Age (2nd millennium b.c.) citadel of Kaymakçı, Turkey. The article presents the results of laboratory x-ray fluorescence (XRF) analysis of both surface and sub-surface samples associated with one excavation area to test the effectiveness of different sample collection strategies by analyzing relationships between sample chemical signatures. The results suggest that a multi-scalar geochemical dataset aids in intra-site feature prospection, site stratigraphy, and nuanced interpretations of the use of space.

Iterative Monte Carlo procedure for quantitative X-ray fluorescence analysis of copper alloys with a covering layer

Monte Carlo simulations with the MCNP code were applied to evaluation of X-ray fluorescence (XRF) data obtained with two laboratory XRF devices. The aim of this investigation was to test an iterative Monte Carlo procedure used for quantitative analysis of copper alloys which were analyzed alone or they were overlapped with a covering layer. The iterative procedure consists of the performance of several Monte Carlo calculations with varying properties of a simulated object to obtain the best agreement of measured and calculated X-ray count rates of identified elements. The attention was paid to high efficiency of the Monte Carlo simulation to achieve shorter time for computing than for XRF measurements. The robustness of the quantitative MC procedure was tested for situations when the experimental conditions are not known exactly.

High-spatial-resolution x-ray fluorescence tomography with spectrally matched nanoparticles

Present macroscopic biomedical imaging methods provide either morphology with high spatial resolution (e.g. CT) or functional/molecular information with lower resolution (e.g. PET). X-ray fluorescence (XRF) from targeted nanoparticles allows molecular or functional imaging but sensitivity has so far been insufficient resulting in low spatial resolution, despite long exposure times and high dose. In the present paper, we show that laboratory XRF tomography with metal-core nanoparticles (NPs) provides a path to functional/molecular biomedical imaging with ~100 µm resolution in living rodents. The high sensitivity and resolution rely on the combination of a high-brightness liquid-metal-jet x-ray source, pencil-beam optics, photon-counting energy-dispersive detection, and spectrally matched NPs. The method is demonstrated on mice for 3D tumor imaging via passive targeting of in-house-fabricated molybdenum NPs. Exposure times, nanoparticle dose, and radiation dose agree well with in vivo imaging.

Effects of hydrous alteration on the distribution of base metals and platinum group elements within the Kevitsa magmatic nickel sulphide deposit

Platinum and nickel are commonly assumed to be immobile in most conditions, especially during low temperature hydrothermal alteration. However, only a small number of studies have rigorously tested this assumption. The Ni–Cu–(PGE) sulphide ore body hosted by the Kevitsa intrusion, northern Finland, provides a natural laboratory to study the behaviour of base metals and platinum group elements (PGE) during low temperature alteration. This ca. 2060Ma mafic–ultramafic intrusion, located in the Central Lapland greenstone belt, hosts disseminated Ni–Cu–(PGE) sulphide mineralisation in the middle part of the main ultramafic body. The mineralisation, which contains a range of Ni, Cu and PGE grades, is affected by three main alterations (serpentinisation, amphibolitisation and epidotisation), and is cross cut by various types of veins. The effect of the circulation of hydrothermal fluids on the distribution of base metals and PGE was studied at two different scales. Interrogation of an extensive deposit-wide assay database provided information on the deposit-scale (kilometre scale) effect of these different alteration styles, and a detailed study, involving laboratory X-ray fluorescence (XRF), portable XRF and micro-XRF mapping, of drill-core samples containing cm-scale cross-cutting veins provided information on the small scale (centimetre to decimetre scale) remobilisation of base metals and PGEs. Results show that the hydration and carbonation of the Kevitsa mineralised mafic–ultramafic intrusion did not significantly affect the distribution of Ni and PGE at scales larger than a few mm, and that Cu and Au are the only metals that are affected by small to large scale remobilisation from centimetre to kilometre scale.

Development and Applications of a Laboratory Micro X-ray Fluorescence (μXRF) Spectrometer Using Monochromatic Excitation for Quantitative Elemental Analysis.

The analytical characterization and an application example of a novel laboratory X-ray fluorescence (μXRF) microprobe is presented, which combines monochromatic, focused X-ray beam excitation with a high-performance silicon drift detector (SDD) and two-dimensional/three-dimensional (2D/3D) scanning capability. Because of the monochromatic excitation, below the (multiple) Compton/Rayleigh scattering peak region, the XRF spectra obtained by this laboratory spectrometer has similarly high peak-to-background ratios as those which can be obtained at synchrotron sources. However, the flux density difference between the proposed laboratory instrument and current synchrotron end stations is on the order of several orders of magnitude. As a result, sub-ppm minimum detection limits (MDL) for transition metals are obtained for a variety of sample matrices. The monochromatic excitation also allows for the efficient use of an iterative Monte Carlo simulation algorithm to obtain quantitative information on the analyzed samples. The analytical characteristics of this instrument and quantitative results, in combination with an iterative reverse Monte Carlo simulation algorithm, will be demonstrated using measurements conducted on an iron-containing meteorite.

Spectral sensitivity of solution 31P NMR spectroscopy is improved by narrowing the soil to solution ratio to 1:4 for pasture soils of low organic P content

Solution phosphorus (P) nuclear magnetic resonance (NMR) spectroscopy following extraction with sodium hydroxide–ethylenediaminetetraacetic acid (NaOH–EDTA) is the most powerful and widely used technique for characterising soil organic P. However, poor spectral sensitivity (related to the signal to noise ratio) can limit its applicability for soils of low organic P content, especially in subsurface layers. Sensitivity can potentially be improved by employing a much narrower (1:4) soil to solution ratio than usual (1:10 or 1:20), which increases the density of P in the NMR tube. Pasture soils were collected at two depths (0–4cm and 4–10cm) from across the high rainfall zone of eastern Australia, and were extracted with NaOH–EDTA at a 1:4 and 1:10 extraction ratio. The extracts were analysed for molybdate-reactive P (i.e. an estimate of inorganic P), and total extractable concentrations of aluminium (Al), iron (Fe), magnesium (Mg), manganese (Mn) and P using inductively coupled plasma optical emission spectroscopy (ICP-OES). Total concentrations of P in soil were determined by laboratory X-ray fluorescence. Extraction efficiency of total soil P was on average only slightly lower for the 1:4 extracts (41%) than for the 1:10 extracts (47%). Extraction efficiencies for paramagnetic (Fe, Mn) and non-paramagnetic (Al, Mg) metals were also similar at the two extraction ratios. Solution 31P NMR spectra of 1:4 extracts were considerably better in terms of spectral sensitivity than those of the 1:10 extracts, particularly for soils of low organic P content. This study demonstrates that in soils of low organic P content, NaOH–EDTA extraction using a 1:4 soil to solution ratio is a viable alternative to the more commonly used 1:10 soil to solution ratio.

Laboratory x-ray fluorescence tomography for high-resolution nanoparticle bio-imaging.

We demonstrate that nanoparticle x-ray fluorescence computed tomography in mouse-sized objects can be performed with very high spatial resolution at acceptable dose and exposure times with a compact laboratory system. The method relies on the combination of the 24 keV line-emission from a high-brightness liquid-metal-jet x-ray source, pencil-beam-forming x-ray optics, photon-counting energy-dispersive detection, and carefully matched (Mo) nanoparticles. Phantom experiments and simulations show that the arrangement significantly reduces Compton background and allows 100 μm detail imaging at dose and exposure times compatible with small-animal experiments. The method provides a possible path to in vivo molecular x-ray imaging at sub-100 μm resolution in mice.

Comparison between XRF, TXRF, and PXRF analyses for provenance classification of archaeological bricks

Ceramics provenance studies based on minor and trace elements are widely used to help in gathering knowledge of local furnace presence and commercial trades. Most of the times, destructive analyses are allowed because of the high amount of material, but sometimes (integer vessels, architectural decorations, etc.), a nondestructive examination is required. In both cases, X‐ray fluorescence (XRF) analysis can be a useful tool.In this work, we compare the classification results obtained on a set of bricks from the medieval Chartusian monastery Certosa di Pavia in the Po valley, northern Italy, exploiting XRF, portable XRF, and total reflection XRF (TXRF) spectrometers.The XRF nondestructive analyses were performed both in situ before sampling and in the laboratory without preparing the shards. Grounded samples were instead used to obtain semi‐quantitative TXRF analysis without dissolving the samples but using a suspension in high‐purified water. The project aimed at verifying if a correct classification was possible even if a quantitative determination of minor and trace elements is abandoned, allowing a faster response when a large amount of data is concerned. For this reason, weight concentration was determined from laboratory XRF measurements only, whereas semi‐quantitative results and entire spectra were considered for TXRF and the in situ campaign, respectively. Data were then submitted to different statistical data treatments to obtain provenance classification. Copyright © 2013 John Wiley & Sons, Ltd.

The use of swept-charge devices in planetary analogue X-ray fluorescence studies

The Chandrayaan-1 X-ray Spectrometer (C1XS) was launched onboard the Indian Space Research Organisation (ISRO) Chandrayaan-1 lunar mission in October 2008. The instrument consisted of 24 swept-charge device (SCD) silicon X-ray detectors providing a total collecting area of ∼ 24 cm2, corresponding to a 14° field of view (FWHM), with the ability to measure X-rays from 0.8–10 keV. One algorithm used to analyse the C1XS flight data was developed at Rutherford Appleton Laboratory (RAL) to convert the raw X-ray flux data into elemental ratios and abundances to make geological interpretations about the lunar surface. Laboratory X-ray fluorescence (XRF) data were used to validate the RAL algorithm, with previous studies investigating how the measured XRF flux varies with target surface characteristics including grain size and roughness. Evidence for a grain-size effect was observed in the data, the XRF line intensity generally decreasing with increasing sample grain size, dependent on the relative abundance of elemental components. This paper presents a subsequent study using more homogeneous samples made from mixtures of MgO, Al2O3 and SiO2 powders, all of grain size < 44 μm, across a broader range of mixture ratios and at a higher level of X-ray flux data in order to further validate the RAL algorithm. For the majority of the C1XS flight data analysed so far with the RAL algorithm, the corresponding lunar ground tracks have been generally basaltic, laboratory verification of the algorithm having been primarily conducted using basaltic lunar regolith simulant (JSC-1A) XRF data. This paper also presents results from tests on a terrestrial anorthosite sample, more relevant to the anorthositic lunar highlands, from where the remaining C1XS lunar dataset derives. The operation of the SCD, the XRF test facility, sample preparation and collected XRF spectra are discussed in this paper.

Rapid, Nondestructive Total Elemental Analysis of Vertisol Soils using Portable X-ray Fluorescence

Portable X-ray fluorescence (PXRF) spectrometry can provide rapid and nondestructive analyses of agriculturally important elements in soil. To assess the applicability of PXRF for total element analysis of Vertisols, 20 soils were collected across northern New South Wales (NSW), Australia. Comparison of PXRF results were made with conventional standard microwave aqua regia (AR) digestion followed by inductively couple plasma optical emission spectroscopy (ICP–OES) analysis, laboratory X-ray fluorescence (LXRF), and neutron activation analysis (NAA). Strong linear correlations were found for As, Ca, Cr, Cu, Fe, K, Mg, Mn, Ni, P, Pb, Si, Ti, and Zn. We demonstrate that nondestructive analyses for total soil element determination, particularly Ca, Fe, Mn, and P, should now allow rapid elucidation of important chemical processes in Vertisols that are commonly only available following rigorous sample preparation and digestion. The integrated and robust character of PXRF instrumentation, requiring minimal or no dedicated laboratory infrastructure, is readily adaptable to a wide range of analytical situations.

A XANES study of cobalt speciation state in blue-and-white glazes from 16th to 17th century Chinese porcelains

The composition of cobalt blue pigments used in ancient blue-and-white Chinese glazes is known to have changed between the 14th and the 17th century and ratios of some main chemical components plus trace elements are relevant guide-lines to establish the porcelain manufacture period. Once archaeological findings of Chinese porcelains can contribute to set up dating processes, a study of blue-and-white porcelain shards recovered during recent excavations in Lisbon Old-City was carried out by non-destructive laboratory X-ray fluorescence spectrometry for chemical characterization, combined with X-ray absorption spectroscopy (XAS) using synchrotron radiation to ascertain the formal valence and coordination of pigmenting cobalt ions. Following a preliminary extended X-ray absorption fine-structure study that revealed a coordination of divalent cobalt ions slightly above four, a detailed analysis of the near-edge region of Co 1s X-ray absorption spectra (XANES) was carried out on the blue-and-white glazes from those archaeological Chinese porcelain fragments. Pre-edge features and edge details are discussed in comparison with XANES spectra obtained from model compounds with well known crystal structure – Co3O4, CoAl2O4 and Co2SiO4, plus a cobalt-based blue pigment (cerulean). Present chemical data validate the manufacture period of studied Chinese porcelains advanced by Art Historians on the single basis of stylistic features (late 16th and medium 17th century). Spectroscopic results confirm a coordination environment of pigmenting Co2+ ions close to tetrahedral and substantiate the dual role of cobalt as network former plus modifier in the glaze of ancient Chinese porcelains.

Laboratory studies into the effect of regolith on planetary X-ray fluorescence spectroscopy

In the analysis of X-ray fluorescence spectra from planetary surfaces, it is traditionally assumed that the observed surface is a plane-parallel, smooth, and homogeneous medium. The spectral and spatial resolutions of the instruments that have been used to measure X-ray emission from planetary surfaces to date have been such that this has been a reasonable assumption, but a new generation of X-ray spectrometers will provide enhanced spectral and spatial resolutions when compared with previous instrumentation. In light of these improvements in performance, it is important to assess how the requirements on the methodology of analysis of spectra may change when the surface is considered as a regolith. At other wavelengths, varying physical properties of planetary regoliths, such as the packing density, are known to have an effect on the observed signal as a function of viewing geometry. In this paper, the results from laboratory X-ray fluorescence measurements of regolith analogue materials at different viewing geometries are presented. Characteristic properties of the regolith such as particle sizes and packing density are found to affect the measured elemental line ratios. A semiempirical function is introduced as a tool for fitting fluorescent line intensity dependences as a function of viewing geometry. The importance of the results is discussed and recommendations are made for the future analysis of planetary X-ray fluorescence data.

A LabVIEW‐controlled portable x‐ray fluorescence spectrometer for the analysis of art objects

AbstractA field‐portable x‐ray fluorescence (XRF) analyzer was developed and assembled at the Academy of Fine Arts in Vienna in order to permit in situ examinations in the field of archeometry. The system is based on energy‐dispersive XRF using an Oxford XTF5011 50‐W x‐ray tube, a Röntec XFlash 1000 silicon drift detector and two lasers as locating devices. A software package based on National Instruments LabVIEW was developed for simultaneous digital control of all system components, for readout of the acquired data and for convenient presentation and preliminary analysis of the spectra. Subsequently, the measured or stored data could be analyzed using a conventional software package such as WinAxil from Canberra Eurisys. In this paper, the system's analytical capabilities are compared with the results obtained using a laboratory XRF system and a comparative evaluation of the two instruments is made. In combination with the overall miniaturization of all devices, it was possible to assemble an easily portable computer‐controlled measurement system which can be used for in situ examinations and studies of, e.g., art objects in museums and galleries, ceiling frescos in churches and cathedrals and archeological findings at the excavation sites. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Development and application of laboratory X-ray fluorescence holography equipment

The X-ray fluorescence holography (XFH) method has drawn the attention of many researchers as a novel experimental technique for imaging a three-dimensional local atomic structure around a certain element in a single crystal. Synchrotron radiation (SR) has been mainly used for the measurements because of extremely weak signals that are about 0.3% of isotropic fluorescent radiation. The measurements limited to the use of a SR source clearly hinder from increasing the number of the users. Thus, we developed a laboratory XFH equipment with a conventional X-ray source by using a singly bent graphite monochromator with a large curvature and X-ray detector for a high counting rate. With this equipment, we have successfully demonstrated that high-quality hologram data of a gold single crystal almost equivalent to those with a SR source are obtained. Four different holograms are recorded in the normal and inverse XFH modes. An atomic image reconstructed from these holograms patterns shows a distinct atomic image of Au

Development of laboratory x-ray fluorescence holography equipment

Laboratory x-ray fluorescence holography equipment was developed. A single-bent graphite monochromator with a large curvature and a high-count-rate x-ray detection system were applied in this equipment. To evaluate the performance of this equipment, a hologram pattern of a gold single crystal was measured. It took two days, which was about one-third the time required for the previous measurements using the conventional x-ray source and several times that using the synchrotron source. The quality of the hologram pattern is as good as that obtained using the synchrotrons. Clear atomic images on (002) are reconstructed.

The Relationship Between the Dust Lead Concentration and the Particle Sizes of Household Dusts Collected in Jersey City Residences

Abstract Lead concentrations measured in total dust samples collected from various environmental surfaces have been used as a surrogate for the lead concentration found in hand dust and subsequently in calculations of lead exposure due to ingestion. However, since the relationship between the characteristics of environmental dust samples and hand dusts is not yet well established, conclusions derived from lead measurements in contaminated household dusts may provide misleading information about childhood exposure. Household dusts collected from seven different residences by a high efficiency particulate air vacuum cleaner were sieved into eight different size fractions (>500, 500 to 355, 355 to 250, 250 to 180,180 to 125, 125 to 90, 90 to 63, and <63 μm) and analyzed for lead in dust (PbD) concentrations using both flame atomic absorption and laboratory X-ray fluorescence. In contrast to results found for street dust, where the PbD concentration increased as the particle size decreased, the reported results indicate that PbD concentration in household dust for six of the seven residences increased as particle size increased. The PbD concentrations in the fractionated dusts ranged between 700 ppm (dust <63 μm in diameter) and 35,300 ppm (dust >500 μm in diameter). Analyses suggested that the dust samples collected from residential environments will have a location-specific distribution of lead concentration that is a function of particle size. The results show that the lead mass and dust mass distributions differed substantially among the seven households as a function of particle size, possibly reflecting different local lead sources, different weathering processes, and different household activities which determine the particle size distribution. For each of these seven Jersey City, New Jersey, household dusts, total PbD concentrations (ppm) were higher than the PbD concentrations (ppm) for particles <125 μm. Leaded paint was the main source of lead-rich particles in the household dusts analyzed in this study. Strong correlations were observed between particle size and concentrations of the elements lead, titanium, and barium in fractionated dust samples known to be rich in leaded paint dust. With the current knowledge suggesting that dust particles which adhere to dry hand surfaces are primarily smaller than 10 μm, this study suggests that there is a potential for overestimating children's blood lead levels by using total PbD concentration as the surrogate for hand dust PbD concentration.