Total Reflection X-ray Fluorescence Spectrometry Research Articles

Evaluation of LEC and VGF-InAs substrates through surface defect characterization and epitaxy growth

Undoped InAs (100) substrate wafers prepared by liquid encapsulated Czochralski (LEC) and vertical temperature gradient freezing (VGF) methods have been studied and compared in their epi-ready state. The substrate surface defects have been analyzed by surface scanner KLA candela, Energy Dispersive X-Ray Spectroscopy (EDAX), Total-reflection X-ray fluorescence spectroscopy (TXRF), with an aim to find the contrast between LEC-InAs and VGF-InAs substrates. It is found that the VGF wafers have lower surface point defects and good stoichiometry compared with the LEC-wafer. VGF-InAs is more favorable to LEC-InAs for oxide thermal desorption and midwavelength infrared（MWIR）epitaxial layer growth with low defect density.

Ultratrace determination of metal ions using graphene oxide/carbon nanotubes loaded cellulose membranes and total-reflection X-ray fluorescence spectrometry: A green chemistry approach

In this paper, the determination of ultratrace heavy metal ions was developed by combining a preconcentration method using graphene oxide/carbon nanotubes membranes (GO/CNTs) and total-reflection X-ray fluorescence spectrometry (TXRF). Due to the excellent adsorptive properties of the GO, the foregoing membranes are suitable for effective simultaneous sorption of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) from aqueous solutions. In this method, the aqueous solution is passed through the GO/CNTs membrane. The analytes are eluted from the GO and afterward transferred onto a siliconized quartz reflector for further TXRF analysis using W and Mo target X-ray tubes. The maximum recoveries for all the elements were obtained at pH 5; thus it was chosen for all further experiments. The face centered central composite design was performed to study the influence of the flow-rate and volume of the solution on the recovery of the determined metal ions. Recovery values higher than 96% for all studied metals allow performing efficient preconcentration with an enrichment factor of 133, achieving the limits of detection (LODs) in the range of 0.08–0.21 ng mL−1 for W target X-ray tube with a measurement time of 2000 s, and much lower LODs for Mo target X-ray tube: 0.001–0.002 ng mL−1 with the exception for Cd (0.11 ng mL−1) with a very short measurement time of 600 s. Certified reference materials of spring water and seawater were examined to verify the reliability of the method. The evaluated procedure does not require toxic reagents or organic solvents, thus minimizes the portion of the sample for TXRF measurement, and stands in good accordance with green analytical chemistry basic principles.

Highly selective and sensitive determination of mercury ions by total-reflection X-ray fluorescence spectrometry

A fast and low-cost method for the highly selective determination of ultra-trace Hg(ii) ions at ppt level using total-reflection X-ray fluorescence spectrometry.

Methodology development and optimization for direct quantification of total selenium concentration in mine water by total-reflection X-ray fluorescence spectrometry

Methodology for direct quantification of total selenium (Se) concentration in mine water by total-reflection X-ray fluorescence (TXRF) spectrometry was developed and optimized. Inductively coupled plasma – mass spectrometry (ICP-MS), as a recognized standard test method, was used as a benchmark for results verification. Preliminary measurements with aqueous multi-element standard solutions showed that Se concentration can be accurately determined down to 10 ng/g by using a single-drop of solution (10 μL) and a measurement time of 600 s. Quantification of lower Se concentration below 10 ng/g was subsequently optimized, also with aqueous multi-element standard solutions. Improvement in detection limit was accomplished by increasing amount of sample deposition as well as increasing measurement time. TXRF analysis of SRM1640a, Trace Elements in Natural Water, was also performed for accuracy check. The developed methodology was applied to analyze five raw mine water samples (MW-1, MW-2, MW-3, MW-4 and MW-5) collected from anonymous mine site locations. TXRF analysis was performed on the as-received samples directly without filtration, dilution and digestion. Samples were prepared as single-drop specimens and analyzed using a measurement time of 600 s. Se and fifteen other elements were detected in varying degree in the as-received samples. Se concentrations quantified by TXRF were 256.5 ± 22.5, 88.4 ± 1.4 and 61.3 ± 2.8 ng/g for mine water samples MW-1, MW-2 and MW-3, respectively, compared to 255.3 ± 5.6, 87.3 ± 2.6 and 59.7 ± 3.5 ng/g by ICP-MS. No clear Se-Kα peak above background was observed for samples MW-4 and MW-5. Increasing amount of sample deposition by preparing triple-drop specimens and using a longer measurement time of 1800 s, allowed a Se-Kα peak to emerge above the background for MW-4, but not MW-5. Se concentration in MW-4 quantified by TXRF was 4.9 ± 0.5 ng/g, compared to 6.7 ± 0.7 ng/g by ICP-MS, which represents an agreement within three standard deviation values between the two techniques. For sample MW-5, even after using triple-drop specimens and increasing the measurement time to 1800 s, Se concentration could not be determined because a Se-Kα peak was not detected by TXRF, compared to the Se concentration of 0.83 ± 0.1 ng/g obtained by ICP-MS. Overall, our analysis results showed that the TXRF technique can be used for direct analysis of total Se concentration in raw mine water samples down to ng/g range, providing high-quality, accurate and repeatable analysis comparable to ICP-MS while requiring much simpler sample preparation.

Total Reflection X-Ray Fluorescence Spectroscopy (TXRF) Method Validation: Determination of Heavy Metals in Dietary Supplements

Dietary supplements may contain heavy metals with the property of bioaccumulation in humans. The aim of this research was to validate and apply two analytical methods to determine Pb, As, Cr, and Hg in dietary supplements by Total Reflection X-ray Fluorescence Spectroscopy (TXRF). Methods validation was conducted through a multivariate analysis using a central composite design (CCD) and a desirability function. Critical values for each study variable were established. The TXRF_DS_1 method was proposed for Pb, As, and Cr determinations, while the TXRF_DS_2 was established for Hg analysis. The digestion method with an acid mixture (HNO3 + HCl + H2O2) was used to break down the organic material of dietary supplements. A solution of 10 μg L−1 Ga was used as an internal standard. Excellent analytical performance was obtained as LODs of 0.59, 0.41, 0.57, and 0.75 μg L−1 and LOQs of 1.95, 1.35, 1.90, and 2.50 μgL −1 for Pb, As, Cr, and Hg, respectively. Calibration curves showed a good linearity for all elements (R2>0.999). Excellent accuracy and precision in measurements (% RSD) was achieved. The real and spiked samples analysis demonstrated the applicability of the TXRF technique (percentage recovery 91–108%). Besides, two samples were analyzed in a comparison study between the TXRF_DS_1 method and the ICP-OES method. The results obtained showed good agreement between both techniques. The TXRF technique allows the analysis of toxic heavy metals in dietary supplements, which are marketed in a wide variety of presentations.

Characterization of archaeological ceramics from eastern Siberia by total-reflection X-ray fluorescence spectrometry and principal component analysis

The study of the composition of archaeological ceramics provides information used to assess possible transportation routes and cultural connections between ancient people living in different regions. Total-reflection X-ray fluorescence (TXRF) was applied for the analysis of ceramics as a promising method due to the rapidity, cost-efficiency, and capability to analyze a very small amount of a sample (<20 mg), which is important for the preservation of archaeological material. Two techniques of sample preparation for the TXRF analysis of ceramics have been considered. The analysis of suspensions was applied to obtain information on the bulk composition of ceramics. Acid leaching was used for the elemental analysis of the clay component of the ceramics, with the separation of non-soluble mineral phase. The proposed TXRF techniques have been successfully validated by the analysis of reference material and comparison with independent analytical methods. Reproducibility (interlaboratory precision) was evaluated for the proposed TXRF leaching method involving two different laboratories. The application of grazing incidence X-ray fluorescence (GI-XRF) showed homogeneous distribution of elements in the specimen and correspondence of the measurements to the conditions of total external reflection. TXRF method was applied to collect the first data on the composition of archaeological samples of ceramics from Popovsky Lug, eastern Siberia (Russia). The obtained data on the elemental composition were used to classify the samples by statistical methods of analysis, including the method of principal components and factor analysis. Three different compositional groups of ceramic have been separated and accepted as corresponding to archaeological interpretation.

Combining Ion Chromatography and Total Reflection X-ray Fluorescence for Detection of Major, Minor and Trace Elements in Quartz-Hosted Fluid Inclusions

The crush-leach technique is a frequently used method to determine the bulk composition of fluid inclusions trapped in a range of geological samples. We present a modified crush-leach technique combining ion chromatography (IC) and total reflection X-ray fluorescence spectroscopy (TXRF) which allows to determine a range of major, minor and trace elements out of one leachate. To date, trace element detection by means of TXRF is barely used in geosciences, although it combines the advantages of low to very low detection limits (µg/L to ng/L range), small sample amount needed (µL-range) and a fast and inexpensive analytical procedure. Previously described problems of adsorption of polyvalent cations at sample surfaces have been overcome by using acidified water as a leachate. Instead, it has been demonstrated that, for example, the syringe filter type used for IC measurements influences contamination and/or adsorption for a number of elements. The proposed method combination was evaluated for accuracy, reproducibility and system blanks and subsequently applied to quartz samples from hydrothermal vein deposits of the Schwarzwald ore district, SW Germany.

Surface analysis of lanthanum strontium cobalt oxides under cathodic polarization at high temperature through operando total-reflection X-ray absorption and X-ray fluorescence spectroscopy

The surface chemistry of perovskite-type lanthanum transition metal oxides is an important parameter in high-temperature electrochemical devices such as solid oxide fuel cells (SOFCs). Strontium segregation on the surface of lanthanum strontium cobalt oxides (LSC) may lead to poor oxygen reduction kinetics. However, previous studies have not sufficiently addressed the oxide surface chemistry, including the oxidation change of LSC under cathodic polarization. In this study, operando total-reflection X-ray fluorescence absorption and X-ray fluorescence spectroscopy were performed to investigate cathodic polarization at high temperature (773 K) and at 1 atm pressure. Dense thin-film electrodes of La0.6Sr0.4CoO3 (LSC113) on Zr0.92Y0.08O1.96 electrolytes with a gadolinium-doped ceria interlayer were examined as model SOFC cathodes. This may be the first time that predominant surface reduction of cobalt is directly observed by using LSC113 under cathodic polarization. This phenomenon is related to strontium enrichment on the LSC surface. (La0.5Sr0.5)2CoO4 decoration on LSC113 enhanced the oxygen reduction kinetics compared with that of bare LSC113. This is due to the suppression of cobalt surface reduction and Sr enrichment in the LSC113 phase.

Improvement of Sensitivity in Total Reflection X-ray Fluorescence Spectrometry by Machine Learning

Improvement of Sensitivity in Total Reflection X-ray Fluorescence Spectrometry by Machine Learning

Total Reflection X-ray Fluorescence spectrometry determination of titanium dioxide released from UV-protective textiles during wash

The aim of this study is to determine the release of TiO2 from six sport garments into the wash water after 1, 2 and 10 washes. For such, Total Reflection X-ray Fluorescence (TXRF) spectrometry was employed for the study of the wash water and Scanning Electron Microscopy - Energy Dispersive Spectrometry (SEM-EDS) was used for the analysis of the textiles. Results showed that the six sport garments released between 0.106 mg/L and 0.352 mg/L after the first two washes and between 0.028 mg/L and 0.337 mg/L of Ti after ten washes. The values found for the Ti amount released in wash water, and consequently into the environment, is much less than other common sources. These results showed the potential of TXRF spectrometry in quantifying Ti in wash water, which is a hard task even for well-established methods. SEM images show that all six samples were weft knitted fabrics, with yarns of approximately 250 μm of width and fibers’ width between 9 and 13 μm.

Evaluation of energy dispersive X-ray fluorescence and total reflection X-ray fluorescence spectrometry for vegetal mass-limited sample analysis: Application to soybean root and shoots

Proper supply of nutrients to plants is mandatory for adequate crop production. Many strategies, such as soil fertilization, nutrient foliar spraying, and seed treatment have been proposed to this goal. Currently, plenty of studies in plant nutrition afford only a low mass of sample for analyses, which is not sufficient for most spectroscopic techniques, including conventional energy dispersive X-ray fluorescence spectrometry (EDXRF). In this context, we developed a new EDXRF method for the determination of nutrients in mass-limited soybean plant tissues.Soybean seeds were treated with different types of Zn suppliers (ZnSO4 and ZnO nanoparticle sources), sowed, and soybean roots and shoots were sampled two weeks after germination. For EDXRF analysis, 20 mg of samples were suspended in 1 mL of deionized water, and 20 μL of the suspension were dried on a 6 μm polypropylene film in an X-ray cup. External calibration using a set of synthetic aqueous cellulose multielemental standards suspended in 1% Triton X-100 proved to be a good strategy for quantification purposes. The trueness of the proposed method was verified analyzing several plant tissue certified reference materials. Additionally, soybean samples were also analyzed by using a validated total reflection X-ray fluorescence (TXRF) method, and good agreement was found between both analytical approaches.To sum up, the proposed EDXRF thin film method is straightforward and reliable for mass limited vegetal sample multielemental analysis and, additionally, follows the green analytical chemistry postulates.

Determination of the Elemental Composition of Dietary Supplements by Total Reflection X-Ray Fluorescence Spectrometry

Techniques for the determination of the elemental composition of dietary supplements (Multifort®, Komplivit®) are presented. It is proposed to use a state-of-the-art analytical method, total reflection X-ray fluorescence spectrometry. The differences in the sample preparation of encapsulated and not encapsulated dietary supplements are described. The effect of encapsulation on the results of the analysis is revealed. The results of qualitative and quantitative analysis are compared with the values certified by the manufacturing company.

Gd(DOTA)-grafted submicronic polysaccharide-based particles functionalized with fucoidan as potential MR contrast agent able to target human activated platelets

Early detection of thrombotic events remains a big medical challenge. Dextran-based submicronic particles bearing Gd(DOTA) groups and functionalized with fucoidan have been produced via a simple and green water-in-oil emulsification/co-crosslinking process. Their capacity to bind to human activated platelets was evidenced in vitro as well as their cytocompatibility with human endothelial cells. The presence of Gd(DOTA) moieties was confirmed by elemental analysis and total reflection X-ray fluorescence (TRXF) spectrometry. Detailed characterization of particles was performed in terms of size distribution, morphology, and relaxation rates. In particular, longitudinal and transversal proton relaxivities were respectively 1.7 and 5.0 times higher than those of DOTAREM. This study highlights their potential as an MRI diagnostic platform for atherothrombosis.

Transfer of metals in the liquids of electronic cigarettes

Objectives: E-cigarettes are electronic devices containing a liquid that usually consists of a mixture of glycerol, propylene glycol and nicotine, with or without flavorings, in various concentrations. A vapor or aerosol is produced, and inhaled from the user, when this liquid is heated by a heating coil. This work examines the impact of three parameters (e-liquid composition, nicotine content and air flow) on the transfer of metals' from the heating coils to the e-liquids.Materials and methods: A distillation unit was used, where 20ml of an e-liquid were boiled with two commercial heating elements. Four e-liquids: 100% Propylene Glycol, 100% Glycerol, 50/50% Propylene Glycol/Glycerol, 33.3/33.3/33.3% Propylene Glycol/Glycerol/Water, three nicotine contents: 0, 0.4 and 0.8% per volume and three air flows: 0, 0.5 and 1.0 L/min, were used. The liquids were analyzed by Total Reflection X-Ray Fluorescence spectrometry to determine the final content of metals.Results and discussion: Five metals, Fe, Ni, Cu, Zn, and Pb, were found to be transferred from the heating coils to the e-liquids. The transfer of those metals increases with air flow and nicotine concentration, while e-liquid composition also has a significant impact. Glycerol enhances the transfer of metals compared to propylene glycol and their mixtures. The boiling temperature of the e-liquids increases significantly the transfer of metals in the e-liquids.Conclusions: There is a transfer of metals from the heating coils to the e-liquids. This transfer depends on the e-liquid composition and on the boiling temperature.

Total-reflection X-ray fluorescence spectrometry as a tool for the direct elemental analysis of ores: Application to iron, manganese, ferromanganese, nickel-copper sulfide ores and ferromanganese nodules

This paper presents a simple and fast method for the determination of major and minor elements in iron, manganese, ferromanganese, nickel‑copper sulfide ores and oceanic ferromanganese nodules by total-reflection X-ray fluorescence spectrometry (TXRF). The preparation of suspension from 5 mL of 1% Triton solution and 20 mg of fine powder with a median particle size of less than 10 μm was used as a sample preparation strategy for direct TXRF analysis. Quantification of elements was performed by the internal standard method. Critical sample mass when the sample could be considered ‘thin’ was calculated for various matrices using Ga as an internal standard. The influence of sampling, particle size, and the internal standard distribution on the reproducibility of the analysis was evaluated. For ore powders with low wettability, preliminarily drying the powder mixed with Ga solution is recommended to increase the uniformity of the distribution of the internal standard. Accuracy was evaluated for S, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, and Pb in ores and nodules and for V, Co, Ni, Sr, Y and As in nodules. TXRF provides fast determination of some major and minor elements in ores and nodules; however, the determination of low levels of elements in the ore matrix can only be considered semi-quantitative.

Total reflection X-ray fluorescence spectrometry for trace determination of iron and some additional elements in biological samples

Trace elements are essential for life and their concentration in cells and tissues must be tightly maintained and controlled to avoid pathological conditions. Established methods to measure the concentration of trace elements in biological matrices often provide only single element information, are time-consuming, and require special sample preparation. Therefore, the development of straightforward and rapid analytical methods for enhanced, multi-trace element determination in biological samples is an important and raising field of trace element analysis. Herein, we report on the development and validation of a reliable method based on total reflection X-ray fluorescence (TXRF) analysis to precisely quantify iron and other trace metals in a variety of biological samples, such as the liver, parenchymal and non-parenchymal liver cells, and bone marrow–derived macrophages. We show that TXRF allows fast and simple one-point calibration by addition of an internal standard and has the potential of multi-element analysis in minute sample amounts. The method was validated for iron by recovery experiments in homogenates in a wide concentration range from 1 to 1600 μg/L applying well-established graphite furnace atomic absorption spectrometry (GFAAS) as a reference method. The recovery rate of 99.93 ± 0.14% reveals the absence of systematic errors. Furthermore, the standard reference material “bovine liver” (SRM 1577c, NIST) was investigated in order to validate the method for further biometals. Quantitative recoveries (92–106%) of copper, iron, zinc, and manganese prove the suitability of the developed method. The limits of detection for the minute sample amounts are in the low picogram range.Graphical abstract

Hollow fiber liquid phase microextraction combined with total reflection X-ray fluorescence spectrometry for the determination of trace level inorganic arsenic species in waters

In the present study, we investigated the possibilities and drawbacks of hollow fiber liquid phase microextraction (HF-LPME) combined with total reflection X-ray fluorescence (TXRF) spectrometry for the determination of low amounts of inorganic arsenic (As) species in water samples. The obtained results showed that a three-phase HF-LPME system was more suitable to be used in combination with TXRF than the two phase configuration, since lower detection limit and better precision for As determination can be attained. Relevant experimental parameters affecting As extraction (i.e. types of extractant, organic solvent, agitation speed, pH and extraction time) and TXRF analysis (deposition volume and drying mode) were systematically evaluated. It was found that As(III) was more efficiently extracted at pH 13, whereas, optimum pH for As(V) extraction was at pH 8.5. Limits of detection (LOD) achieved using the best analytical conditions meet the requirements of current legislation and allow the determination of inorganic As(V) and As(III) in water. The proposed method was also applied to different spiked environmental water samples for the preconcentration and subsequent determination of trace inorganic As species.

Monitoring dissolved active trace elements in biogas plants using total reflection X‐ray fluorescence spectrometry

Generally, full‐scale biogas plants require trace elements supplementation to sustain a stable process. The aim was to apply total reflection X‐ray fluorescence (TXRF) to monitor the dissolved, active elements, for the first time, at μg/L levels in biogas plants. The digester liquid is comparable to sludge with high solids content and high salt concentrations. The ions are usually measured in the dried fermenter slurry after acid digestion in its inactive bound form, although microorganisms can take up only dissolved ions as active agent. In this study, a procedure was developed to monitor dissolved ions in such environmental processes to prevent an overdose or underdose. The analytical figures of merit considered were the lowest possible limit of detection, the recovery of spiked ions and linearity. Samples were spiked with nickel, selenium and tungsten in the range of 10–200 μg/L. Highest recovery rates of &gt;93% for concentrations of 10 to &lt;100 μg/L were obtained after the samples were centrifugated twice, followed by application of microwave‐assisted acid digestion. The calculated lowest limit of detection was 2–4 μg/L. The developed method was first tested in laboratory‐scale biogas digesters with wheat straw as substrate. Successful application of TXRF was also achieved in a full‐scale biogas plant to estimate the dynamics of “active” trace element ions in the range of 2–1,000 μg/L for several months. Therefore, cost‐effective biogas plant management is possible through the application of TXRF spectrometry to monitor trace elements.

Development and validation of a method for multielement analysis of apatite by total-reflection X-ray fluorescence spectrometry

Apatite group of minerals incorporates a large range of trace metals such as Sr, Y, U, Th, as well as the rare earth elements, that allows obtaining useful information on their genesis and could be used in several applications in geology and geochemistry. In this study, a new method for the multielement analysis of apatite using total-reflection X-ray fluorescence spectrometry (TXRF) was developed. The acid digestion procedure was chosen as an optimal sample preparation with the capability to analyze a low sample amount (~5–10 mg). The validation of the method passed through the combination of procedures: analysis of Durango and Otter Lake well-known apatite samples; using inductively coupled plasma mass spectrometry and wavelength-dispersive X-ray fluorescence spectrometry as reference analytical methods; assessment of the measurement uncertainty. The proposed TXRF method is advantageous in being fast, cheap and simple for the multielement analysis of apatite with high accuracy.

Quantification of recycled rubber content of end-of-life tyres in asphalt bitumen by total-reflection X-ray fluorescence spectrometry

This article presents a new methodology developed to quantify the amount of crumb rubber used in asphalt bitumen by Total-reflection X-Ray Fluorescence (TXRF) spectrometry. For the evaluation of the crumb rubber content in rubberized binders, the samples were completely digested by microwave-assisted acid digestion in a mixture of HNO3:HF acids. TXRF spectrometry has proven to be a powerful analytical technique capable to detect up to 12 elements in these matrixes with detection limits of only a few ppb's (μg/L). From those elements, Zn was elected as indicator of recycled crumb rubber and used for its quantitative correlation. The results obtained show that the proposed methodology is capable of quantifying the content of recycled crumb rubber in asphalt bitumen in a robust, accurate and reproducible way.