XRF Systems Research Articles

Benchtop x-ray fluorescence to quantify elemental content in nails non-destructively

Metals continue to impose health issues among world populations. A non-invasive alternative biomarker for assessment of metals and other elements has been explored in other studies using toenail samples. Some benefits of using toenails as biomarkers over blood samples include cost efficiency, ease of collection, and a longer biological half-life within samples. The objective of this study was to employ desktop XRF for the purpose of measuring metal concentrations in human nail samples, thus conducting a non-destructive assessment. These benefits paired with comparable accuracy in exposure detection could prove toenail samples to be a preferred biomarker for many studies. Current elemental quantification techniques in toenail samples could be improved. The standard practice for measuring metal exposure in toenails, inductively coupled plasma mass spectrometry (ICP-MS), has a counterpart in x-ray fluorescence. While maintaining similar quantification capabilities, x-ray fluorescence could provide decreased cost, preservation of samples, and ease of operation. Portable XRF machines have been tested for measuring toenail samples, but they have drastically increased detection limits in comparison to ICP-MS. New benchtop XRF systems should give comparable detection limits to ICP-MS. This study compares the benchtop XRF measurements of lead (Pb), copper (Cu), iron (Fe), and Selenium (Se) levels to that of ICP-MS measurements of toenail samples and calculates estimated detection limits for 23 other elements. We found strong correlations for the toenail lead (R2 = 0.92), copper (R2 = 0.95), selenium (R2 = 0.60), and iron (R2 = 0.77) comparison between desktop XRF and ICP-MS measurements. Median minimum detection limits over the 23 elements were found to be 0.2 μg/g using a 7.5-min measurement. Benchtop XRF provides a lower detection limit than previously studied portable XRF machines, which gives it the capability of accurately detecting almost any desired element in nail samples. Benchtop XRF provides a non-destructive alternative to ICP-MS in surveillance of nail samples.

Combined in situ XRF–LIBS analyses as a novel method to determine the provenance of central Mediterranean obsidians

This work presents a new calibration method for determining the provenance of obsidian artefacts based on the combined use of XRF and laser-induced breakdown spectroscopy (LIBS). At first, obsidian samples collected from the main Mediterranean sources were characterized using portable XRF and LIBS systems. After data treatment, elemental information was used to carry out principal component analysis (PCA) for each technique. Rb, Sr, Zr, Y and Fe elements, detected by using XRF, were found to be the key parameters enabling obsidians discrimination. Likewise, LIBS data helped differentiating the analysed patterns by the intensity of their main elemental components (Ca, Al, Mg and K). After selecting the key parameters detected by each technique, a new data matrix combining XRF and LIBS data was finally built. According to PCA results, the discrimination of Mediterranean sources based on combined XRF–LIBS data ensured a higher reliability over mono-analytical models, by increasing the Euclidean distance between sources projections over three-dimensional principal components plots. Knowing that the representativeness of elemental data could be compromised by the presence of superficial degradation products or deposition patinas, a shot-to-shot comparison of in-depth LIBS analyses is finally proposed as a method to disclose whether the spot under analysis was superficially contaminated or altered. Thus, the proposed strategy based on the combined use of portable XRF and LIBS spectrometers could be particularly useful for the in situ analysis of obsidian artefacts that underwent superficial alteration or could be covered by patina products.Graphical abstract

In‐house manufactured benchtop XRF spectrometer

AbstractThe growing efficiency of agribusiness depends on the development of technology. A key challenge regards the determination of plant mineral content, which help farmers to make a decision about fertilizer use. Currently, such nutritional status diagnoses are made based on wet chemical methods; they are usually slow and generate chemical wastess. In this context, an in‐house manufactured XRF benchtop for agri‐samples is proposed in this study. This XRF system was furnished with a manual primary filter changer, vacuum chamber, dual interlock radiological protection system, which were installed in the equipment cover, and light signals. Analytical capabilities were also evaluated. The equipment presented spurious peaks of Ti, Fe, Ni, and Zn, which is not ideal for some agronomical applications; this issue might be overcome in the future by means of additional primary filters. The total x‐ray spectrum counting rate is roughly one magnitude order lower than two other commercial XRF systems, but the signal‐to‐noise ratio is quite similar. The vacuum chamber under partial vacuum improves the Al, Si, P and S signals from 1.5 to 2.2. The limits of detection (LOD, mg kg−1) for P (261), S (168), K (68), and Ca (50) macronutrients and Mn (14), Fe (15), Cu (9), and Zn (8) micronutrients are close to the ones reported in the literature. The limits of detection for P, S, K, and Ca are suitable for plant analysis.

Some developmemt and improvement of ED XRF tecniques in Mongolia

The Nuclear Research Center, National University of Mongolia, Ulaanbaatar has got three ED XRF systems with isotope sources (Fe-55, Cd-109, Am-241, Co-57) from 1976, secondary target from 1981 and total reflection X-ray techniques from 1993. This facility is used for training, research and analytical services.

Analysis of multi-layer thin-film materials using benchtop XRD and XRF systems

Analysis of multi-layer thin-film materials using benchtop XRD and XRF systems

Portable ED-XRF as a tool for optimizing sampling strategy: The case study of a Hellenistic amphora assemblage from Paphos (Cyprus)

Provenance studies of archaeological ceramics based on their elemental composition illuminate the production and distribution of pottery vessels and, in the case of transport containers, of the commodities that they contained. A basic assumption is that the elemental composition of ceramics from a specific workshop or production area can be distinguished from other production groups, mainly because of the use of geochemically different clays, either singly or in combination. In some cases, however, the compositional differences between production groups are quite small. Thus, laboratory methods with high performance, in terms of precision and accuracy, such as neutron activation analysis (NAA) or wavelength dispersive X-ray fluorescence (WDXRF), are often preferred for analyzing archaeological ceramics, especially for effective comparison with reference groups and published data from other studies. Handheld portable energy dispersive XRF systems (pXRF), although increasingly used during recent years, offer lesser analytical performance, which may obscure compositional differences and currently do not offer the same potential for comparison to known reference groups. However, due to their potential for fast and non-invasive measurements, considerably larger numbers of samples can be analysed by pXRF, offering an array of advantages. We argue that pXRF offers the opportunity for an initial analytical survey of a large ceramic assemblage as the basis for efficient sample selection for laboratory analysis, covering a large number of samples and avoiding for the generation of redundant measurements. We present the application of such a stepped analytical approach to a well-studied assemblage of amphorae of the Hellenistic period at Nea Paphos, Cyprus. The analysis of 287 amphora fragments by pXRF, the grouping of that data to select samples for further analysis of 97 individuals by NAA, and the comparison of the grouping of data from both chemical techniques is presented. This leads not only to archaeological insights on the production and circulation of amphorae, but tests an innovative methodology that offers the chance to maximize and extend the application of geochemical techniques of high accuracy and precision on an assemblage-wide scale.

Comparison of the performance of two handheld XRF instruments in the study of Roman tesserae from Cástulo (Linares, Spain)

Cultural Heritage objects are frequently unavailable for transportation to laboratory facilities due to their size, location or local Cultural Heritage preservation regulations. The development of handheld XRF (hXRF) systems has, therefore, proven to be essential in the study of unmovable objects. In this study, two handheld XRF instruments—Bruker™ Tracer III SD® and Olympus™ Innov-X Delta Premium—were compared and evaluated using tesserae from the Mosaico de los Amores (Linares, Spain). Given their portability, the user-friendly nature of their operating systems and their overall performance, both hXRF instruments are highly recommended for in situ campaigns in Cultural Heritage studies. However, the detection limits calculated for each element point towards a better detection of low-Z elements when using the two-beam mode of the Olympus™ Innov-X Delta Premium hXRF. This study underlines the importance of systems that allow the analysis of the same point with analytical conditions optimized for different chemical elements.

Development of X-ray fluorescence methods by use of a Mo X-ray tube and their application in the case of biological samples

In the present work two different experimental arrangements, aiming in the X-ray fluorescence analysis of solid and liquid biological samples respectively, were developed and studied both theoretically and experimentally in combination with a Mo anode X-ray tube: The secondary target XRF (STXRF) and the Total Reflection XRF set-up (TXRF). The secondary target XRF irradiation chamber was designed and constructed in our laboratory. Careful choice of the materials combined with the tight geometry used, minimize the presence of interference peaks in the spectrum and offer high intensity of the exciting beam at the sample position. Optimum performance was ensured by means of an extended theoretical and experimental study of various parameters affecting the analytical capabilities of secondary target XRF systems, such as: The choice of secondary target material and the operational conditions of the X-ray tube. The secondary target XRF set-up was applied in the determination of the concentrations of trace elements in a pool blood serum sample. A simple preparation technique, like the freeze-drying process was employed, resulting in detection limits of 15 ng/ml for most metal trace elements and for a 6000 sec measuring time. The accuracy of the whole experimental procedure, examined by internal standardization and by analyzing the reference standard material A-13, was found to be about 4% over the whole atomic number range. For the determination of the mass absorption coefficients, necessary in the quantification step, a modified version of the emission transmission method was employed. Total Reflection X-Ray Fluorescence (TXRF) is a well-established method, mainly applied in the analysis of liquid samples, offering very low detection limits in most of the cases. Direct application of the TXRF method is not so efficient in blood serum analysis, since the high content of the organic matrix increases significantly the background due to Compton scattering. Chemical treatment of the blood serum samples and related preconcentration techniques have been suggested in literature, but they are time consuming and increase the possibility of adding contaminants in the sample. In this work, the applicability of direct TXRF analysis in blood serum samples was examined. The insertion of a Mo filter after the cut-off reflector has been found to improve significantly the peak to background ratio, especially for the elements of interest such as Cu, Zn, Se and Br. The influence of self-absorption phenomena in the quantification procedure was also investigated with respect to the internal standard used and the sample mass analyzed. Precision and accuracy in the analysis was found to be about 4% over the whole atomic number range. Detection limits were in the order of 25ng/ml for most metal trace elements and a measuring time of 3600 sec.

Portable X-ray fluorescence (PXRF) spectrometry of earth materials: considerations for forensic analysis

Abstract Miniaturization of components and other advances in technology have resulted in significantly increased availability of portable X-ray fluorescence spectroscopy (PXRF) units, leading to a boom in their use in a variety of fields. An unfortunate corollary, however, is that there has also been a boom in the publication of data of doubtful quality, based on misunderstandings of PXRF and the underlying physics of X-ray fluorescence. Many manufacturers sell the units as point-and-shoot black boxes, capable of generating usable data under a range of conditions but, in reality, all of the assumptions and limitations inherent in laboratory-based XRF systems still apply or are even amplified in portable units. This paper highlights some of the areas of highest concern to alert readers and practitioners alike, and provides examples of some issues that may arise during analysis.

Quality Assessment Statistic Evaluation of X-Ray Fluorescence via NIST and IAEA Standard Reference Materials

The aim of this study is a quality assessment of X-ray fluorescence laboratory located at the University of Khartoum. The X-ray fluorescence spectrometer system consists, a set of three 109Cd sources of an initial nominal activity of 10 μCi, and Si(Li) detector Energy Dispersive XRF(EDXRF) systems. It is important to carry out this work because it has an effective contribution for a wide range of research and services. The assessment was carried out by measuring 8 NIST-2709a (soil) and 13 IAEA-155 (milk powder) standard reference material samples for repeatability examinations to test the measurement precision. The total combined standards uncertainty values for XRF lab were estimated by an error from repeatability measurements adding 2.6% for error propagation related to the method. For accuracy assessment, three standard statistic approaches were applied, i.e. the Bias %, zeta-score, and En-number. The bias of all elements for both standard materials was found to be within a deviation range from −28% to 7.8%. The results of all elements for both the zeta-score test and En-number have satisfactory results except Th (Thorium) and Zr (Zirconium) which consider as questionable results for NIST SRM 2709a and unsatisfactory results for En-number.

사다리꼴 필터를 이용한 효율적인 중첩펄스 처리 알고리즘 구현

X-선과, γ-선을 이용한 형광분석장치는 현재 널리 쓰이는 물질의 고유특성을 분석하는 장치이다. 하지만 여러 가지 원인으로 인해 장치사용 시 측정 신호에서 중첩 현상이 발생한다. 검출 신호의 높이는 측정 물질의 특성을 반영하며 측정 물질을 정확히 분석하기 위해서는 중첩된 신호를 제거하거나 복원을 해야 한다. 현재 trapezoidal 필터는 형광분석장치에 널리 사용되고 있으며 중첩펄스 검출에서도 좋은 결과를 보이고 있다. 본 논문에서는 측정 신호의 사다리꼴 변형에 기반 한 중첩펄스 처리방법을 제안한다. 제안방법은 사다리꼴 필터를 이용한 최대값 검출 알고리즘에 두 개의 카운터와 몇 개의 레지스터만을 추가하여 추가적인 중첩펄스 처리 알고리즘을 구현하기 때문에 기존 방법에 비해 하드웨어 복잡도가 훨씬 적으면서도 정확히 중첩펄스를 처리 할 수 있다.

XRF시스템용 효율적인 Trapezoidal 필터 및 최대값 검출 회로 설계

XRF 시스템에서 디지털 방식으로 펄스를 합성하는 기술은 현재 다양하게 발전 되면서 기존의 아날로그 방식을 대신하고 있다. XRF 시스템에서는 펄스의 높이를 분석하기 위해 주로 trapezoidal 필터를 사용한다. 본 논문에서는 trapezoidal 필터의 하드웨어 구현을 위한 효율적인 구조를 제안한다. 또한 측정 오차가 기존 알고리즘에 의한 오차의 절반으로 감소되면서 효율적인 하드웨어 구현이 가능한 최대값 검출 알고리즘을 제안한다. 제안한 알고리즘은 하드웨어 언어인 Verilog HDL로 설계하고 FPGA로 구현하였으며 테스트보드를 제작하여 성능을 검증하였다.

X‐Ray fluorescence as an assay tool for musculoskeletal nutrition animal research

XRF techniques are well established for the measurement of the presence of lead and heavy metals in osseous tissue. The advent of compact pyroelectric crystal x‐ray generators and silicon drift detectors presents a new opportunity for nutrition research that studies muscular, vascular and epithelial tissue. We compare the measurable ratios of Fe/K, Fe/Ca, and Fe/Cl in different bovine muscle tissues to establish a baseline feasibility study in preparation for in‐vivo measurements. The low power and portability characteristics of new technology XRF systems make it possible to examine epithelial tissue characteristics of animals in‐vivo. Limited initial calculations and models with backscattered x‐rays utilizing non‐imaging optics indicate promise. Non‐imaging optics are used to increase the effective collecting area of the spectral detection system in the backscatter configuration. We propose the concept that strategically selected ion ratios in muscle and vascular tissues can aid in quantifying “nutritional health” in laboratory animals. We acknowledge institutional support.

An interlaboratory comparison of bone lead measurements via K-shell X-ray fluorescence spectrometry: validation against inductively coupled plasma mass spectrometry

(109)Cd-based K-shell X-ray fluorescence spectrometry (hereafter, for brevity, XRF) is used, often in epidemiological studies, to perform non-invasive, in vivo measurements of lead in bone. We conducted the first interlaboratory study of XRF via the circulation of nine goat tibiæ in which the mean lead value ranged from 4.0 µg g(-1) to 55.3 µg g(-1) bone mineral. The test tibiæ were subsequently analyzed via nitric acid digestion followed by lead determination by inductively coupled plasma mass spectrometry (ICP-MS) - along with certified reference materials for bone lead - thus providing measurement traceability to SI units. Analysis of dried bone for lead via nitric acid digestion and ICP-MS yields mass fraction data in units of µg g(-1) dry weight. The mean bone lead value based on ICP-MS analysis ranged from 1.8 µg g(-1) to 35.8 µg g(-1) dry weight. For comparison purposes, XRF-measured Pb values (µg g(-1) bone mineral) were converted into the ICP-MS-measured units (µg g(-1)dry weight bone) by multiplying the former by the average ash fraction from the nine tibiæ. Eight of the XRF systems did not yield a significant bias for any of the nine tibiæ; one system was biased for one of the tibiæ; two systems were biased for two tibiæ; one system was biased for four tibiæ; two systems (813-1 and 804-2) were biased for five tibiæ and one system (801-1) was biased for six of the nine tibiæ. Average bias for the systems (under those particular operating conditions) that were biased for the majority of samples ranged from -2.6 µg g(-1) (-15.7%) to 5.1 µg g(-1) (30.7%) dry weight bone. All participants now have the ICP-MS data, allowing any corrective actions deemed necessary to be implemented. The ICP-MS data, however, indicated that the lead mass fraction varied considerably with the sampling location within the tibiæ, to the extent of exceeding XRF variability for the higher lead values. Material heterogeneity is an unavoidable reality of measuring lead in bone.

The use of a European coinage alloy to compare the detection limits of mobile XRF systems. A feasibility study

AbstractThe investigation of archaeological and historical materials makes use of techniques that, though borrowed from other fields of research and industrial production, frequently have to be ‘re‐invented’ because of peculiar characteristics of the analysed objects. Artistic relevance, limited movability, compositional and structural heterogeneity radically change the experimental approach and often require ad hoc designed equipment. These considerations also apply to x‐ray fluorescence, especially regarding mobile systems. The extensive development and use of mobile spectrometers has produced an extremely diversified context and created the need for common criteria to evaluate their performances as well as the advisability of a survey on the existing equipment.This paper shows the feasibility of such an idea through a demonstrative survey that was carried out among users of different mobile x‐ray fluorescence spectrometry (XRF) systems in the areas of Rome, Italy and Valencia, Spain. The experimental protocol was based on measuring spectrometer detection limits with the single standard method. The standard was the 50 eurocent coin, whose alloy is made of 89% Cu, 5% Al, 5% Zn, 1% Sn; the large spread of the European currency guarantees maximum availability. The experimental data show that the use of different x‐ray tubes and detectors results in detection limits that may differ from each other by a factor of 6 for Zn and almost 100 for Sn; despite the large number of variables that in principle affect the performance, it was observed that the high voltage of the x‐ray tube is the most important parameter. Copyright © 2007 John Wiley & Sons, Ltd.

Analysis of Fuels, Lubricants, and Greases Using X-ray Fluorescence Spectrometry

Abstract X-ray spectrometry (XRF) is a versatile instrumental method for elemental analysis in a wide variety of materials. The performance of three different XRF systems will be compared: a high power wavelength dispersive x-ray spectrometer (WDXRF), a low-power WDXRF, and a bench-top energy dispersive instrument (EDXRF). The data obtained show quite clearly the large difference in sensitivities between instruments. This translates into varying lower limits of detection (LLD) or quantification and sample throughput. For quantitative analysis well above the LLD, the accuracy of the results obtained on the different instruments is similar, or — for practical purposes of quality control in many applications — the differences in accuracy between the different instruments can be considered insignificant. Most of the applications and methods developed by a variety of laboratories and regulatory organizations are applicable to specimens of a specified nature and matrix. Some of the more versatile procedures include a method to account for differences in matrix between standard reference materials and unknowns. One of the effects that is usually neglected in this case is the wedge effect, which is caused by the fact that the volume that is excited by the beam and the volume from which characteristic radiation can be observed are not the same and vary (for a given spectrometer system) depending upon the density and the quantity of the sample. This effect will be illustrated and discussed.

Focus on Analytical Equipment

Focus on Analytical Equipment

A new Monte Carlo program for computing low-energy gamma- and x-ray propagation in an axially-symmetric XRF system

Annular XRF systems, using backscattering geometry, have advantages of convenience of use, but it is difficult to predict their sensitivity to concentrations of heavy metals at different depths, or the contribution of scattered radiation to the background. A Monte Carlo program has therefore been developed to carry out calculation of this type. Several variance-reduction techniques are included. Preliminary results for the detection of platinum are given.

Source-to-sample distance independent efficiency technique for XRF analysis

A technique to make the detection efficiency in XRF systems less dependent on source-to-sample distance is presented. It is shown that this dependence can be made more constant within a large range of distances if a properly calculated annular mask is used. Experimental results (for Ca, Ti, V and Zr), in good agreement with the calculated ones, are presented and show that constant efficiency values within ±5% can be obtained when the sample distance varies from 3 to 12 mm. However, peak absolute efficiencies are then reduced by a factor of about five.

Applications of XRF, NAA and low-kV radiographic techniques in the study of body composition and diseased tissue

Members of this group have responded to a number of challenging health issues by attempting to devise sensitive XRF, NAA and low-kV radiographic measurement systems foboth in vivo and in vitro applications. These studies are generally either of toxicological importance, examine potential for diagnosing the presence of disease, or offer effective means for monitoring potentially harmful side-effects of therapy. Particular examples include the in vivo XRF investigation of human skeletal uptake of Pb in working and living environments, in vivo XRF monitoring of elevated levels of Fe in skin (indicating the presence of an undesirable side-effect of the treatment of thalassaemia), in vivo NAA monitoring of elevated levels of Al in bone (indicating an undesirable side-effect of the treatment of chronic renal failure) and in vitro characterization, by means of low-kV imaging, of a range of calcification parameters in healthy and diseased breast tissue. The latter investigation has been conducted in association with an in vitro NAA study of concentrations of trace elements in the same types of tissue. Figures of merit for the various measurement systems have been obtained in terms of minimum detectable levels and concentrations (MDL's and MDC's) and where applicable, image related parameters.