Total Reflection X-ray Fluorescence Analysis Research Articles

Dual energy-band excitation from a low power Rh anode X-ray tube for the simultaneous determination of low Z and high Z elements (Na-U) using total-reflection X-ray fluorescence analysis (TXRF).

This article presents results from an experimental setup for a dual energy-band vacuum spectrometer for total-reflection X-ray fluorescence analysis allowing simultaneous efficient excitation of low, medium, and high Z elements. The spectrometer is equipped with an air-cooled 35 W low power Rh X-ray tube and a 17 mm2 silicon drift detector with a thin 8 µm beryllium window. A Pd/B4C multilayer monochromator is used at the same time as a Bragg reflector for Rh-Kα radiation and as a high-energy cut-off reflector above 5 keV, where the characteristic Rh-L radiation is totally reflected and present in the spectrum of the exciting radiation. This leaves one broad low energy band below 5 keV and one high energy band around the energy of Rh-Kα. As Rh-L radiation would be absorbed on its path through air, a new beam entrance system was designed in order to guide the Rh-L photons into the vacuum chamber for efficient excitation of low Z elements. With this setup, elements down to sodium (Z = 11, E = 1.04 keV) could be detected. First results are presented, and spectra obtained in air as well as in vacuum are compared and discussed. Detection limits in the range of 1000 µg/kg for Na and around 140 µg/kg for Mg were achieved using the NIST SRM 1640 (trace elements in water).

Mercury determination at trace levels using membrane preconcentration and benchtop total reflection X-ray fluorescence analysis

At present, there is a considerable interest in Hg monitoring in water samples due to its widespread occurrence and the high toxicity of most of its compounds. Hg determination in water samples by means of total reflection X-ray fluorescence spectrometry (TXRF) entails some difficulties due to the high vapour pressure and low boiling point of this element that produce evaporation and loss of Hg from the surface of the reflector during the drying process, commonly employed in sample preparation in TXRF analysis.In a former work we demonstrated the usefulness of PVC-based membranes functionalized with dithizone for Hg preconcentration. Limits of detection as low as 0.8 μg·L−1 Hg were obtained using a 1 kW TXRF system. The main goal of the present research was to improve the extraction system and to apply it in combination with low power TXRF instrumentation (50 W). In this sense, some extraction parameters as well as measurement conditions such as the volume of membrane deposited on the quartz reflector, the agitation speed during extraction, the aqueous sample volume and the measurement time were carefully evaluated to obtain the maximum sensitivity for Hg determination. Using the best analytical conditions, a limit of detection for Hg of 0.3 μg·L−1 was obtained which is adequate according to the limits of current legislation on the quality of water for human consumption. Additionally, a morphological study of the preconcentrated sample on the quartz reflector was performed by optical microscopy and information regarding Hg distribution along the membrane was obtained by μ-XRF analysis. It was found that Hg is not homogenously accumulated on the membrane and thus, the size of the membrane on the reflector is a critical parameter that has to be controlled to ensure the complete exposure of the loaded membrane to the X-ray beam. This fact is of special relevance when using this preconcentration approach in combination with micro-TXRF. Finally, to further prove applicability of the TXRF method for real water sample analysis, different types of spiked water samples were analysed.

Determination of uranium in immersion liquid of demolition waste using total reflection X-ray fluorescence analysis

In this study, we proposed a novel methodology based on total reflection X-ray fluorescence (TXRF) analysis for rapid evaluation of uranium radioactivity concentration in water samples, which will be found in the decommissioning field of Fukushima Daiichi Nuclear Power Plant containing various impurities. Sample solutions were prepared by mixing a multi-element standard solution containing uranium and thorium with an immersion liquid of the demolition debris in order to examine the effect of components of the demolition debris. An indium standard solution was added to the samples as an internal standard. Since the Rb Kα peak overlapped with the U Lα and Th Lα peaks, Gaussian fitting was performed to determine the net intensity of the U Lα peak. Moreover, due to the largely different contents of uranium and rubidium, reducing the number of fitting parameter made the Gaussian fitting easier. To determine the widths of the peaks, long-time TXRF measurement of the standard solutions for each element was performed. In the Gaussian fitting, only the peak intensities were considered as fitting parameters because the peak widths and peak energies could be fixed. The relative intensity of the U Lα peak was calculated as the net intensity of the U Lα peak normalized by that of the In Kα peak. The relative intensity was directly proportional to the uranium concentration. The estimated minimum detection limit of uranium with a measurement time of 15 min was significantly lower than the effluent standard value for uranium concentration in drainage water as defined by the Japanese Water Pollution Prevention Law, 20 mBq/cm3. All in all, we believe that this method will be useful in determining the uranium concentration in drainage water in the decommissioning field of Fukushima Daiichi Nuclear Power Plant.

Simultaneous determination of silver and gold nanoparticles by cloud point extraction and total reflection X-ray fluorescence analysis

While the nanoscale dimensions give metallic nanoparticles unique physical and chemical properties, their potential release in the environment and subsequent effects on ecosystem health are becoming an increasing concern. In the present contribution, for the first time, a novel and simple analytical approach has been developed for the simultaneous quantification of silver and gold nanoparticles (AgNPs, AuNPs) in aqueous samples. The method combines a sample preparation and enrichment step based on cloud point extraction (CPE) with total reflection X-ray fluorescence spectrometry (TXRF) detection. Experimental conditions enabling the simultaneous extraction and detection of AgNPs and AuNPs were studied in detail. Under the best analytical conditions, limits of detection for AgNPs and AuNPs were 0.3 and 0.2 μg L−1, respectively. Due to the lack of suitable certified references materials, accuracy of the CPE-TXRF method was tested by analysing several types of spiked water samples, including mineral, tap, river and sea water. Percentage recoveries achieved for the analysis of spiked samples were in all cases in the range of 82–100% for both types of studied NPs, suggesting that the existence of natural colloids, ionic Ag+ and Au3+ species, and other components in environmental waters have little influence on the quantitative determination of AgNPs and AuNPs. The only exception was the recovery obtained in the analysis of the spiked sea water sample that was around 40–50%. However, for salty aqueous samples, the developed analytical approach might still be feasible if the standard addition method is used for calibration purposes. In an attempt to provide additional information on AgNPs and AuNPs behaviour in the environment, the CPE-TXRF method was also applied to study the influence of organic matter content in waters as well as the influence of soil matrix on AgNPs and AuNPs stability.

Characterization of As-polluted soils by laboratory X-ray-based techniques coupled with sequential extractions and electron microscopy: the case of Crocette gold mine in the Monte Rosa mining district (Italy).

Arsenic concentration and distribution were studied by combining laboratory X-ray-based techniques (wavelength dispersive X-ray fluorescence (WDXRF), micro X-ray fluorescence (μXRF), and X-ray powder diffraction (XRPD)), field emission scanning electron microscopy equipped with microanalysis (FE-SEM-EDX), and sequential extraction procedure (SEP) coupled to total reflection X-ray fluorescence (TXRF) analysis. This approach was applied to three contaminated soils and one mine tailing collected near the gold extraction plant at the Crocette gold mine (Macugnaga, VB) in the Monte Rosa mining district (Piedmont, Italy). Arsenic (As) concentration, measured with WDXRF, ranged from 145 to 40,200mg/kg. XRPD analysis evidenced the presence of jarosite and the absence of any As-bearing mineral, suggesting a high weathering grade and strong oxidative conditions. However, small domains of Fe arsenate were identified by combining μXRF with FE-SEM-EDX. SEP results revealed that As was mainly associated to amorphous Fe oxides/hydroxides or hydroxysulfates (50-80%) and the combination of XRPD and FE-SEM-EDX suggested that this phase could be attributed to schwertmannite. On the basis of the reported results, As is scarcely mobile, even if a consistent As fraction (1-3g As/kg of soil) is still potentially mobilizable. In general, the proposed combination of laboratory X-ray techniques could be successfully employed to unravel environmental issues related to metal(loid) pollution in soil and sediments.

Investigations on the binding of ethylmercury from thiomersal to proteins in influenza vaccines

This study investigates the binding of ethylmercury (EtHg+) released from the preservative thiomersal by hydrolysis to proteins in influenza vaccines via ultrafiltration and subsequent total reflection x-ray fluorescence (TXRF) analysis as well as size exclusion chromatography (SEC) hyphenated to inductively coupled plasma-mass spectrometry (ICP-MS).Binding of EtHg+ to the protein fraction was shown by means of ultrafiltration and TXRF in a qualitative matter. SEC/ICP-MS was applied to gain more information about the molecular weight of the bound protein and quantitative information. First experiments showed the necessity of a rinsing step during elution with a thiol-containing compound to prevent unspecific binding or mercury species to the chromatographic system. Adduct formation of EtHg+ and a high-molecular compound could be observed for different concentrations of EtHg+ applied. The mercury-containing fraction was larger than 133 kDa, indicating binding to hemagglutinin, which is the active ingredient in influenza vaccines. The applied SEC/ICP-MS method allowed for external calibration with EtHg+ and a binding of 141 μg L−1 Hg was shown for a vaccine solution that was incubated with EtHg+ (25 mg L−1 Hg).

Detection Limits of a TXRF Analysis System in Double Reflection Mode

Total reflection X-ray fluorescence (TXRF) analysis system is described with regard to develop a new prototype in double reflection mode. We discuss the basic principles of the technique to design and set-up a new TXRF module, coupled to an old X-ray generator. Different geometries are analyzed and the system is calibrated with standard solutions of several elements and the detection limits are established in the range of 4 x 10-11 to 13 x 10-11 g. Finally, a certified standard sample is measured and the results are compared for all studied geometries. This research is focused on the analysis of micro traces, in scientific and technological applications.

Evaluation of a sample preparation procedure for total-reflection X-ray fluorescence analysis of directly collected airborne particulate matter samples

This paper investigates in detail a sample preparation procedure for the total-reflection X-ray fluorescence (TXRF) analysis of airborne particles using a three-stage Dekati™ PM10 cascade impactor. The impactor was modified in such a way, that 30 mm diameter quartz reflectors suitable for TXRF spectrometers can be inserted as collection plates below the impactor's nozzle arrays with cut-off diameters of 10, 2.5 and 1 μm. Smaller particles are collected in a backup filter, which can be analyzed using classical energy-dispersive XRF. As an internal standard 5 ng Y were pipetted centrally onto each reflector after collection. The reflector surface has to be coated in order to reduce particle bounce-off. Two surface coatings, silicone oil and petroleum jelly (“Vaseline”), were compared in this study. Before TXRF analysis this coating layer was removed by low-temperature oxygen plasma ashing. A new approach was introduced, which involves masking of the quartz reflectors in order to remove the outer ring of the spot pattern, which consists of two concentric circles, and to produce a sample, which lies entirely inside the detectable area. Results of this approach were compared to those obtained from unmasked samples and discussed in detail. Angle scans show residue-like behavior of the samples in each stage. Samples were taken on the roof of the Atominstitut building in January 2017 on 10 days during working hours.

Analysis of coke beverages by total-reflection X-ray fluorescence

The influence of the organic content, sample preparation process and the morphology of the depositions of two types of Coke beverage, traditional and light Coke, have been investigated by mean of Total-reflection X-ray Fluorescence (TXRF) spectrometry. Strong distortions of the nominal concentration values, up to 128% for P, have been detected in the analysis of traditional Coke by different preparation methods. These differences have been correlated with the edge X-ray energies of the elements analyzed being more pronounced for the lighter elements. The influence of the organic content (mainly sugar) was evaluated comparing traditional and light Coke analytical TXRF results. Three sample preparation methods have been evaluated as follows: direct TXRF analysis of the sample only adding internal standard, TXRF analysis after open vessel acid digestion and TXRF analysis after high pressure and temperature microwave-assisted acid digestion. Strong correlations were detected between quantitative results, methods of preparation and energies of the X-ray absorption edges of quantified elements. In this way, a decay behavior for the concentration differences between preparation methods and the energies of the X-ray absorption edges of each element were observed. The observed behaviors were modeled with exponential decay functions obtaining R2 correlation coefficients from 0.989 to 0.992. The strong absorption effect observed, and even possible matrix effect, can be explained by the inherent high organic content of the evaluated samples and also by the morphology and average thickness of the TXRF depositions observed. As main conclusion of this work, the analysis of light elements in samples with high organic content by TXRF, i.e. medical, biological, food or any other organic matrixes should be taken carefully. In any case, the direct analysis is not recommended and a previous microwave-assisted acid digestion, or similar, is mandatory, for the correct elemental quantification by TXRF.

Development and characterization of sub-monolayer coatings as novel calibration samples for X-ray spectroscopy

With the advent of both modern X-ray fluorescence (XRF) methods and improved analytical reliability requirements the demand for suitable reference samples has increased. Especially in nanotechnology with the very low areal mass depositions, quantification becomes considerably more difficult. However, the availability of suited reference samples is drastically lower than the demand. Physical vapor deposition techniques have been enhanced significantly in the last decade driven by the need for extremely precise film parameters in multilayer production. We have applied those techniques for the development of layer-like reference samples with mass depositions in the ng-range and well below for Ca, Cu, Pb, Mo, Pd, Pb, La, Fe and Ni. Numerous other elements would also be possible. Several types of reference samples were fabricated: multi-elemental layer and extremely low (sub-monolayer) samples for various applications in XRF and total-reflection XRF analysis. Those samples were characterized and compared at three different synchrotron radiation beamlines at the BESSY II electron storage ring employing the reference-free XRF approach based on physically calibrated instrumentation. In addition, the homogeneity of the multi-elemental coatings was checked at the P04 beamline at DESY. The measurements demonstrate the high precision achieved in the manufacturing process as well as the versatility of application fields for the presented reference samples.

Green synthesis of copper oxide nanoparticles impregnated on activated carbon using Moringa oleifera leaves extract for the removal of nitrates from water

AbstractThe present work aims at impregnating copper oxide nanoparticles (Cu NPs) on activated carbon by means of green synthesis with Moringa oleifera leaf extract to develop a material to remove contaminants from water. The produced materials were characterized by means of their textural (specific surface area), morphological (Transmission Electron Microscopy), and structural (X‐ray Diffraction) properties. Particles size was estimated by Scherrer equation and the elemental copper concentrations were estimated by Total Reflection X‐ray Fluorescence (TXRF). Adsorption experiments, as well as pH, kinetics, and adsorption isotherms studies were carried out with the intent of evaluating the efficiency of nitrate (NO3‐) removal from water. The impregnation efficiency of Cu NPs on activated carbon after the adsorption process was measured by means of TXRF analyses. Characterization results confirmed the formation, impregnation, and stability of copper oxide nanoparticles supported on activated carbon, whose crystallite average size ranged between 6 and 61 nm. The proposed method for the nanoparticles synthesis and impregnation were demonstrated to be simple and eco‐friendly. Impregnated carbons presented significant nitrate removal (about 60 %) thus indicating their potential application in water treatment.

A first evaluation of the analytical capabilities of the new X-ray fluorescence facility at International Atomic Energy Agency-Elettra Sincrotrone Trieste for multipurpose total reflection X-ray fluorescence analysis

The aim of the work is to present a systematic evaluation of the analytical capabilities of the new X-ray fluorescence facility jointly operated between the International Atomic Energy Agency and the Elettra Sincrotrone Trieste for multipurpose total reflection X-ray fluorescence analysis.The analytical performance of the XRF beamline end-station (IAEAXspe) was systematically evaluated under TXRF excitation geometry by analyzing different types of aqueous (lake, waste and fresh water) and solid (soil, vegetal, biological) certified reference materials using an excitation energy of 13.0keV (for the purpose of multielemental analysis). The results obtained for both types of samples in terms of limits of detection and accuracy were also compared with those obtained using laboratory X-ray tube based TXRF systems with different features (including Mo and W X-ray tube systems). Taking advantage of the possibility to work under high vacuum, the IAEAXspe set-up instrumental sensitivity was also determined using an excitation energy of 6.2keV to explore the possibilities for light elements determination.A clear improvement of the element detection limits is achieved when comparing this facility to conventional X-ray tube based TXRF systems highlighting the benefits of using the monoenergetic synchrotron exciting radiation and the ultra-high vacuum chamber in comparison with conventional laboratory systems.The results of the present work are discussed in view of further exploitation of the facility for different environmental and biological related applications.

Sample preparation for total reflection X-ray fluorescence analysis using resist pattern technique

A circular resist pattern layer with a diameter of 9mm was prepared on a glass substrate (26mm×76mm; 1.5mm thick) for total reflection X-ray fluorescence (TXRF) analysis. The parallel cross pattern was designed with a wall thickness of 10μm, an interval of 20μm, and a height of 1.4 or 0.8μm. This additional resist layer did not significantly increase background intensity on the XRF peaks in TXRF spectra. Dotted residue was obtained from a standard solution (10μL) containing Ti, Cr, Ni, Pb, and Ga, each at a final concentration of 10ppm, on a normal glass substrate with a silicone coating layer. The height of the residue was more than 100μm, where self-absorption in the large residue affected TXRF quantification (intensity relative standard deviation (RSD): 12–20%). In contrast, from a droplet composed of a small volume of solution dropped and cast on the resist pattern structure, the obtained residue was not completely film but a film-like residue with a thickness less than 1μm, where self-absorption was not a serious problem. In the end, this sample preparation was demonstrated to improve TXRF quantification (intensity RSD: 2–4%).

Comprehensive approach to the validation of the standard method for total reflection X-ray fluorescence analysis of water

In this work, we present the validation of the chemical method for total reflection X-ray fluorescence (TXRF) analysis of water, proposed as a standard to the International Standard Organization. The complete experimental procedure to define the linear calibration range, elements sensitivities, limits of detection and quantification, precision and accuracy is presented for a commercial TXRF spectrometer equipped with Mo X-ray tube. Least squares linear regression, including all statistical tests is performed separately for each element of interest to extract sensitivities. Relative sensitivities with respect to Ga, as internal standard, are calculated. Accuracy and precision of the quantification procedure using Ga as internal standard is evaluated with reference water samples. A detailed discussion on the calibration procedure and the limitation of the use of this method for quantitative analysis of water is presented.

Total reflection X-ray fluorescence as a convenient tool for determination of trace elements in microscale gasoline and diesel

Quantitative determination of trace elements like S, Fe, Cu, Mn and Pb in gasoline and S in diesel is of great importance due to the growing concerns over air pollution, human health and engine failure caused by utilization of gasoline and diesel with these harmful elements. A method of total reflection X-ray fluorescence (TXRF) was developed to measure these harmful trace elements in gasoline and diesel. A variety of factors to affect measurement results, including TXRF parameters, microwave-assisted digestion conditions and internal standard element and its addition, were examined to optimize these experimental procedures. The hydrophobic treatment of the surface of quartz reflectors to support the analyte with neutral silicone solutions could prepare thin films of gasoline and diesel digestion solutions for subsequent TXRF analysis. The proposed method shows good potential and reliability to determine the content of harmful trace elements in gasoline and diesel with high sensitivity and accuracy without drawing different standard calibration curves, and can be easily employed to screen gasoline and diesel in routine quality control and assurance.

Total Reflection X-Ray Fluorescence Determination of Rare Earth Elements in Mineral Water Using a Combined Preconcentration Technique

ABSTRACTA combined approach for the simultaneous determination of lanthanum, cerium, praseodymium, neodymium, and samarium in mineral water in the range from · 10−2 to 101 µg/L by total reflection X-ray fluorescence analysis is reported. The combined technique of preconcentration of the rare earth elements ions includes the codeposition of their hydroxides on a collector and dispersive liquid–liquid microextraction by chloroform to form complexes with 1-(2-pyridylazo)-2-naphthol. The results for the determination of lanthanum and light lanthanides in natural water samples with the combined approach are in good agreement with measurements obtained by inductively coupled plasma–mass spectrometry.

Synthesis of Titanium Dioxide Nanoparticles Using Echinacea purpurea Herba.

Nowadays green synthesis of metal nanoparticles is a developing area of research. In this study, titanium dioxide nanoparticles were biosynthesized using an aqueous solution of Echinacea purpurea herba extract as a bioreductant. This is novel and interesting method for synthesis of TiO2 nanoparticles. The prepared titanium dioxide nanoparticles were characterized using ultraviolet-visible spectroscopy (UV-VIS), transmission electron microscopy (SEM), total reflection X-Ray fluorescence analysis (TXRF) and Fourier-transform infrared spectroscopy (FTIR). The size of TiO2 nanoparticles was found to be in the range of 120 nm. Moreover, the alkaline reaction of the solution (pH = 8) resulted in the increase in absorbance (280 nm), which facilitates the growth of the number of TiO2 nanoparticles in the studied solution. Also, synthesis of TiO2 nanoparticles using green resources like Echinacea purpurea herba is a better alternative to chemical synthesis, since this green synthesis is pollutant-free and eco-friendly.

Trace Elemental Determination Using a Portable Total Reflection X-Ray Fluorescence Spectrometer with a Collodion Film Sample Holder.

Using a portable total-reflection X-ray fluorescence (TXRF) spectrometer with a collodion film sample holder, a spectrum of an analyte containing 50 ng of aluminum was measured. The Al Kα line (1.49 keV) that partially overlaps with the Si Kα line (1.74 keV) from a quartz glass substrate usually used as a sample holder for TXRF analysis, was clearly detected when using the collodion film sample holder. To investigate the quantitative performance of the portable spectrometer with a collodion film sample holder, the concentrations of Cr, Mn, and Fe in a certified reference material of river water (JSAC 0302-3b), whose certified values are 10.0, 5.1, and 59.6 μg/L, respectively, were determined by the internal-standard method. We showed that approximate concentrations of these elements were determined.

Elemental analysis of tree leaves by total reflection X-ray fluorescence: New approaches for air quality monitoring

This work shows that total reflection X-ray fluorescence (TXRF) is a fast, easy and successful tool to determine the presence of potentially toxic elements in atmospheric aerosols precipitations on tree leaves. Leaves are collected in eleven parks of different geographical areas of the Brescia city, Northern Italy, for environmental monitoring purposes. Two sample preparation procedures are considered: microwave acid digestion and the novel SMART STORE method for direct analysis. The latter consists in sandwiching a portion of the leaf between two organic foils, metals free, to save it from contamination and material loss. Mass composition of macro, micro and trace elements is calculated for digested samples, while relative elemental amount are obtained from direct analysis. Washed and unwashed leaves have a different composition in terms of trace elements. Differentiation occurs according to Fe, Pb and Cu contributions, considered as most representative of air depositions, and probably related to anthropogenic sources. Direct analysis is more representative of the composition of air precipitations. Advantages and drawbacks of the presented methods of sample preparation and TXRF analysis are discussed. Results demonstrate that TXRF allows to perform accurate and precise quantitative analysis of digested samples. In addition, direct analysis of leaves may be used as a fast and simple method for screening in the nanograms range.

Reduction of Spectral Interference between X-ray Peaks Originating from an X-ray Tube and X-ray Fluorescence Peaks in Total Reflection X-ray Fluorescence Analysis

Reduction of Spectral Interference between X-ray Peaks Originating from an X-ray Tube and X-ray Fluorescence Peaks in Total Reflection X-ray Fluorescence Analysis