Energy Dispersive X-ray Fluorescence Instrument Research Articles

Application of the k-Means Algorithm and the Gaussian Mixture Model (GMM) – African Vulture Optimization Algorithm (AVOA) for the Resolution of Overlapping Energy-Dispersive X-Ray Fluorescence (EDXRF) Peaks

Limitations in instrument resolution mean that soil samples analysis using energy-dispersive X-ray fluorescence (EDXRF) often produced overlapping spectral peaks of heavy metals with similar energies. This overlapping of spectral peaks posed a significant problem in the quantitative analysis of heavy metals in soil samples. Therefore, it was necessary to decompose the overlapping peaks. In this paper, a new method for decomposing overlapping peaks was presented in the context of Gaussian Mixture Model (GMM) parameter estimation, combining the k-means algorithm and the African Vulture Optimization Algorithm (AVOA). The data acquired from EDXRF instruments were preprocessed before being input to the k-means algorithm, which produces the output used to initialize the parameters of the GMM. Subsequently, AVOA was employed to optimize the GMM parameters based on a fitness function derived from the data. Ultimately, the optimized GMM parameters obtained through the AVOA process yield the optimal solution for the decomposition of overlapping peaks. This approach effectively addressed the challenge of peak overlap in the determination of heavy metals in soil by EDXRF. Soil samples were obtained from national standard samples, peach gardens, and vegetable-growing regions. The results showed that the maximum absolute errors for the peak channel and peak area were 1.46% and 6.37%, respectively. A comparison of the proposed model with others models indicated that the k-means-GMM-AVOA model exhibits the best performance in terms of speed, accuracy, and stability.

Application of the US EPA procedure for determining method detection limits to EDXRF measurement of filter-based aerosol samples

ABSTRACT The US Environmental Protection Agency (USEPA) modified its guidance on determining “method detection limits” (MDL) in 2017. The recommended procedures have not yet been applied to the analyses routinely done on filter samples for USEPA’s Chemical Speciation Network (CSN). This paper applies the new USEPA procedure for estimating MDL to Energy Dispersive X-Ray Fluorescence (EDXRF) analysis of atmospheric aerosol samples collected on filters. The procedure involves estimating MDL by two approaches – statistical distributions of unloaded blank sample measurements and lightly loaded, spiked samples – and sets the MDL as the maximum of these two approaches. Spiked samples at low concentrations were developed using an aerosol deposition chamber to follow this approach. The MDL procedure was initially conducted on one EDXRF instrument, and the spike-based MDL was found to be higher than blank-based MDL for 28 of the 31 elements. The blank-based MDL was higher than the spike-based MDL for Si, K and Fe, which are common contaminants present in filter raw media or arising from EDXRF hardware. The annual verification performed using five EDXRF analyzers demonstrated that the MDL estimated following the USEPA procedure was stable over time and analyzers for all elements except K, which yielded a higher MDL. Implications: Lightly loaded reference materials (RM) were developed for Energy Dispersive X-ray Fluorescence (EDXRF) measurements of elemental concentrations in filter-based particulate matter samples using a novel aerosol generation chamber. These RM were then used to estimate method detection limits (MDL) following U.S. Environmental Protection Agency guidance. These new MDL estimates were compared to alternative estimates and, for most elements, are higher. Our work provides EDXRF users with MDL estimates for each element and an assessment of different MDL estimation approaches.

Building ED-XRF datasets for sourcing rhyolite and quartzite artifacts: A case study on the Homa Peninsula, Kenya

Determining the provenance of archeological material is essential for documenting the movement of ancient resources and placing fossils and artifacts in the correct stratigraphic context. Non-destructive geochemical compositional analysis with Energy Dispersive X-ray Fluorescence (ED-XRF) spectrometry has the potential to provide a versatile approach to studying the provenance of archeological material. It is possible to build large regional XRF datasets that are useful for understanding the movements of toolmakers because this technique can be applied to a large number of samples non-destructively. However, incorporating new provenance data into existing datasets poses several potential challenges. Expanded provenance datasets often require the comparison of geochemical data across XRF instruments and settings. In particular the addition of different lithologies requires an understanding of diverse degrees of surface weathering and matrix heterogeneity.On the Homa Peninsula in Kenya, Oldowan tools from Kanjera South were previously linked to primary and secondary sources based on trace element geochemistry determined through ED-XRF. In this study, we established comparability across two ED-XRF instruments and incorporated samples from additional sources of quartzite and rhyolite into the existing raw material sourcing dataset. The new sources revealed regional differences in the geochemistry of rhyolite and quartzite that derive from drainages on and around the Homa Peninsula. This demonstrates the compatibility of quartzite and rhyolite materials with non-destructive ED-XRF sourcing and provides a methodological establishment of cross-study comparison in elemental values derived from non-uniform whole rock samples. This study highlights the importance of calibration using overlapping reference standards and linear regressions to determine offsets necessary for direct comparison.

Technical note: Rapid mineral determination in forages by X-ray fluorescence

A large portion of the cow's ration is composed of forages that can vary greatly in mineral concentrations, which may affect animal performance and health. Current methods for mineral analysis require sample destruction either through wet or dry ashing and complex analytical techniques for individual minerals. Energy dispersive X-ray fluorescence (EDXRF) is a nondestructive, multi-mineral, spectroscopy technique, which makes mineral quantification simple, direct, and affordable. The study objective was to evaluate the prediction performance of EDXRF of Na, Mg, P, S, Cl, Ca, K, Mn, Fe, Cu, and Zn concentrations in forages. Twelve certified plant samples with a wide range in mineral concentrations were used to develop calibrations, and 35 forages (18 alfalfa hays, 10 grass hays, 7 corn silages) with measured mineral concentrations, which were collected over several years from 3 proficiency programs, were used as an independent validation set. All the samples were previously dried and finely ground and were prepared by compressing them into a round dense pellet, 40 mm in diameter, using a 40-ton pneumatic laboratory press. Samples were scanned using an EDXRF instrument enhanced for lighter minerals like Na and Mg. Samples were scanned at 20 keV and at 40 KeV associated with an Al filter, for a total analysis time of approximately 6 min. Calibrations were developed with Bruker SpectraEDX (Bruker, Hamburg, Germany) software and optimized to minimize the standard error of calibration. All of the minerals had acceptable calibration performance with coefficient of determination ranging from 0.93 (P) and 0.99 (Cl, Ca, and Mn) and coefficients of variation within 5 to 14%, which are similar to the coefficients of variation of the reference analysis. The coefficients of variation for Na was an exception, with a coefficients of variation of 29%. The validation set obtained similar statistical results as that observed in calibration. The root mean square error of prediction corrected for bias was similar to the standard error of calibration, indicating that it is possible to build a robust calibrations that performed well across different type of forages by using 12 reference samples with a sufficient range in mineral concentrations that were determined accurately. A bias correction was necessary to improve prediction accuracy only for K (-0.23% dry matter) and Ca (-0.16% dry matter). Energy dispersive X-ray fluorescence demonstrated the ability to be an accurate, direct, and simple technique for forage mineral analysis.

Multi-element detection in sea water using preconcentration procedure and EDXRF technique

A method was optimized for detecting trace elements in sea water using Energy dispersive X-ray fluorescence (EDXRF) technique. Sea water samples were pre-concentrated using ammonium pyrrolidinedithiocarbamate (APDC) as chelating agent and methyl isobutyl ketone (MIBK) as organic phase. The preconcentrated samples were dried to form thin films on mylar substrate and analysed using EDXRF spectrometer. The multi-element standard samples prepared in synthetic sea water were used for EDXRF instrument calibration. The instrument was calibrated for 11 elements namely As, Cd, Co, Cr, Fe, Ga, Pb, Se, Sc, V and Zn using linear regression method for concentration up to 200 ppb. The detection limits achieved for As, Cd, Co, Cr, Fe, Ga, Pb, Se, Sc, V and Zn were 13, 70, 5.1, 36, 15, 36, 23, 11, 20, 13 and 40 ppb respectively. The optimized method was used for determination of elements in sea water collected from the Thane creek, Mumbai, India. The results were checked for accuracy by comparing it with inductively coupled plasma atomic emission spectroscopy (ICP AES) technique. The comparison showed the discrepancy of results to be insignificant at 95% confidence level.

Distribution of Heavy Metals in Surface Sediments of the Bay of Bengal Coast.

The concentrations of major (Si, Al, Ca, Fe, and K) and minor (Cd, Mn, Ni, Pb, U, Zn, Co, Cr, As, Cu, Rb, Sr, and Zr,) elements in the surficial sediments were studied in an attempt to establish their concentration in the Bengal coast. It was revealed that the majority of the trace elements have been introduced into the Bengal marine from the riverine inflows that are also affected by the impact of industrial, ship breaking yard, gas production plant, and urban wastes. The concentration of heavy metals was measured using Atomic Absorption Spectroscopy and Energy Dispersive X-ray fluorescence instruments. The highest concentrations for several trace elements were thus recorded which generally decrease with distance from the coast. It was observed that the heavy metal concentrations in the sediments generally met the criteria of international marine sediment quality. However, both the contamination factor and pollution load index values suggested the elevation of some metals' concentrations in the region. Constant monitoring of the Bengal coast water quality needs to be recorded with a view to minimizing the risk of health of the population and the detrimental impacts on the aquatic ecosystem.

Figure of merit for spectrometers for EDXRF

How should one select the best detector for a particular measurement in energy dispersive X‐ray fluorescence (EDXRF)? How should one select the optimum system configuration, i.e. the best shaping time and beam current? Manufacturers provide a variety of specifications, such as energy resolution and maximum count rate, but these are indirectly related to the end use of an EDXRF instrument, the measurement and detection limit of the measured elemental concentrations.We suggest in this paper using the time required to achieve a given statistical uncertainty as a figure of merit. We derive scaling rules for this figure of merit based on conventional specifications, including energy resolution, peaking time, maximum count rate, detector area, and intrinsic efficiency. These scaling rules also include the peak to background ratio of a photopeak and the number of overlapping peaks. We then show how this figure of merit can be used to select the optimum detector and spectrometer configuration for specific applications and compare the results to data obtained with typical systems. Copyright © 2012 John Wiley & Sons, Ltd.

Chemometric analysis of EDXRF measurements from fossil bone

Bone chemistry is an important source of biological and environmental information. Elemental compositions of archaeological and fossil bone have granted insight into the diets of ancient humans and other animals, as well as informing about the burial conditions of bone. Chemical studies of ancient bone can be performed non‐destructively with portable energy‐dispersive X‐ray fluorescence (EDXRF) spectrometers, which is particularly advantageous for on‐site analyses of museum specimens. Portable EDXRF instruments carry some analytical disadvantages, however, which may result in reduced precision or accuracy. Analytical shortfalls may be overcome by analysing inter‐sample trends in EDXRF spectral data instead of reported concentration measurements. We investigated the utility of statistically treating handheld EDXRF spectra from fossil bone and teeth, specifically the normalisation and mean centering of spectral data before principal component analysis. Fossil bone and tooth specimens were sourced from two Pleistocene localities in the Western Cape of South Africa, Swartklip 1 and Elandsfontein Main. Samples from the two localities could be distinguished using principal component score values, and coefficient loadings allowed chemical interpretation of the score clusters. Swartklip 1 samples were associated with elevated concentrations of Ca, indicating an additional Ca‐bearing mineral (i.e. calcite), whereas Elandsfontein Main samples were associated with elevated Fe and Sr concentrations. Fossil bone chemistry could be related to groundwater percolation through the sedimentary matrices of each locality. The methodology behind the case study presented here could readily be applied elsewhere and would be particularly useful to handheld EDXRF studies of museum specimens. Copyright © 2011 John Wiley & Sons, Ltd.

Chemical Environment Effects on Kβ/Kα Intensity Ratio: An X-ray Fluorescence Experiment on Periodic Trends

X-ray fluorescence (XRF) data from an energy-dispersive XRF instrument were used to investigate the chlorine Kα and Kβ peaks in several group 1 salts. The ratio of the peak intensity is sensitive to the local chemical environment of the chlorine atoms studied in this experiment and it shows a periodic trend for these salts.

Application of Small-Spot Energy Dispersive X-ray Fluorescence Instrumentation in Phytoremediation Activities around Metal Mines

In view of the considerable number of analyses necessary in phytoremediation and plant biology studies, it is important that the analytical procedures used for elemental determination in plant tissues should be fast and cheap, with simple sample preparation, and of adequate accuracy and precision. The aim of the present work was focused on the possibilities and drawbacks of a low-cost benchtop energy dispersive X-ray fluorescence (EDXRF) instrument to be used as an analytical technique for studying the potential use of sunflowers (Helianthus annuus) for the phytoremediation of an abandoned Pb/Zn mining area. The simplicity and the ability to operate at room temperature and open air conditions provides a flexible setup for the rapid analysis of vegetation material without complicated previous sample pretreatments. With the help of different collimator caps, a modest lateral resolution (from 200 mum to 1 mm) was achieved and it was thought to be small enough to study the accumulation of Pb and Zn and its distribution between parts of the vegetation specimens (roots, stems, and leaves); the limits of detection achieved (0.6 ng for Zn and 3.0 ng for Pb) proved to be suitable for the intended purpose. Therefore, obtained data revealed that EDXRF spectrometry could be a useful tool to better understand the metal uptake, translocation, and tolerance mechanisms in vegetation species related to biomonitoring and phytoremediation studies.

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

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

Sulfur determination on stone monuments with a transportable EDXRF system

AbstractAn important part of the world's cultural heritage is represented by stone monuments. A very dangerous weathering process that deteriorates stone monuments and is caused by human activity is air pollution. One of the worst pollutants for stone monuments is associated with sulfur compounds, especially with gypsum. Gypsum is a rather soluble compound that may be washed away by rain. It leaves the surface of the stone clean but eroded and open to new corrosive processes.With transportable energy dispersive x‐ray fluorescence (EDXRF) instruments it is possible to conduct in situ investigations, mappings, registrations and evaluations of the stone‐degradation phenomena related to sulfate formation on stone and stone‐like materials by quantifying sulfur concentrations directly associated with the presence of gypsum.The EDXRF instrument used in this project is a commercial system comprising a miniaturized low‐power, air‐cooled tungsten x‐ray tube and a silicon drift detector (SDD) Peltier‐cooled detector.The EDXRF instrument was calibrated using a series of standard samples specifically developed for this project with a sulfur content ranging from 0.5 to 15%. Correlating the sulfur peak counts with sulfur concentrations, a straight calibration line (R2 = 0.9985) was obtained. Several high voltage levels of the x‐ray tube were tried to define the best operating conditions. The silicon escape peak of calcium had to be accounted for owing to its interference with the sulfur peak.In this paper we shall discuss the working method adopted and the results achieved following the examination of a number of stone monuments such as the “Fanciulla di Anzio” and other ancient Roman statues housed in the Roman National Museum, and the Sarcophagus of Pope Boniface VIII sculpted by Arnolfo di Cambio and situated in the Crypt of the Vatican Basilica. Copyright © 2007 John Wiley & Sons, Ltd.

Soil Characterization by Energy Dispersive X-Ray Fluorescence: Sampling Strategy for in situ Analysis

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

Information from Lateral Scans of Single Hairs by X-Ray Fluorescence

Abstract The trace metal content of hair has been used for many years as an indicator of the level in many biological systems. In the study of the aftermath of a tragic case of mercury poisoning from the consumption of bread made from grain seeds which had been treated with methymercury as a fungicide, a definite relationship between the blood level and the concentration found in the hair was determined. Some of the children born of pregnant women who had eaten the grain were affected and others were not. To obtain a more precise time and magnitude of the maximum concentration in the blood, a special energy dispersive X-ray fluorescence instrument (XRF) was built to determine the concentration of mercury in a one mm. segment of a single hair. It also had the capability of measuring a number of other elements simultaneously. The profiles of the concentrations of other elements along a single hair showed important information not given by analysis of the entire hair which gives only an average. It is recommended that every hair investigation start with a profile scan of a single hair, and an instrument capable of doing this has recently come on the market.