Total Reflection X-ray Fluorescence Research Articles

Towards a calibration of laboratory setups for grazing incidence and total-reflection X-ray fluorescence analysis

Grazing-Incidence X-ray fluorescence (GIXRF) analysis, which is closely related to total-reflection XRF, is a very powerful technique for the in-depth analysis of many types of technologically relevant samples, e.g. nanoparticle depositions, shallow dopant profiles, thin layered samples or even well-ordered nanostructures. However, the GIXRF based determination of the depth-dependent information about the sample is usually based on a modeling of the experimental data. This requires profound knowledge of the geometrical parameters of the setup employed, especially the incident beam profile as well as the detector aperture parameters. Together they determine the incident angle dependent so-called effective solid angle of detection which must be known in order to model any experimental data set. In this work, we demonstrate how these instrumental parameters, which are typically not known with sufficient accuracy, can be determined using dedicated experiments with a well-known calibration sample. In addition, this paves the way for a full calibration of the setup, as also information about other parameters, e.g. the incident photon flux is gained. Here, we are using a commercially available instrument for this demonstration but the principle can also be applied for other GIXRF setups.

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.

Features of sample preparation techniques in the total-reflection X-ray fluorescence analysis of tea leaves

Tea is a popular drink around the world and contains essential minerals and trace elements for human health. In this study, the analytical capabilities of the total-reflection X-ray fluorescence method (TXRF) were considered for the analysis of tea. Different sample preparation techniques, e.g. suspension, open vessel acid digestion, and microwave acid digestion were examined. The influence of particle size was investigated in the analysis of the suspension of tea samples. Mass-absorption coefficients for the tea matrix and the critical surface density of the specimen were calculated. The data obtained explain the presence of absorption effects in the determination of P, S, Cl, and K in suspensions. The digestion procedure is chosen as an optimal sample preparation technique for the TXRF analysis of tea. Nineteen real tea samples were analyzed using TXRF. The advantages of TXRF have been presented through the comparison of results with the wavelength-dispersive X-ray fluorescence spectrometry method.

X-ray Fluorescence Techniques in Determining the Habitat Preferences of Species-Ulva pilifera (Ulvales, Chlorophyta) from Montenegro Case Study.

The paper presents four new sites where bright green Ulva thalli were found inhabiting freshwater (a river, a ditch, the Milet Canal) and marine (on the rocky shore of the Adriatic Sea) habitats in Montenegro. The aims of this study were to determine, for the first time, whether specimens of Ulva pilifera collected in Montenegro are phylogenetically and morphologically the same species as the one occurring in Europe. Using total reflection X-ray fluorescence (TXRF) and wavelength dispersive X-ray fluorescence (WDXRF) techniques it assessed the elemental composition of their thalli and its influence to colonise new habitats. Elements: Al, As, Ba, Br, Ca, Cl, Cr, Cu, Fe, Hf, I, K, Mg, Mn, Na, Ni, P, Pb, Rb, S, Si, Sr, Ti, V, and Zn were determined. The highest elemental concentrations were found for Ca = 16.3% (using WDXRF) and for Sr = 292 ppm (using TXRF) in the Ulva thalli. Ulva pilifera analysed from Montenegro, based on classical morphological methods and molecular techniques, are closely related to the same species from inland and coastal waters throughout Europe. The analysis of trace elements showed that the metal content in Ulva thalli is correlated with the trace elements in water and sediments. Ulva pilifera fits numerous features that make it one of the bioindicators of marine pollution, thanks to its worldwide distribution and capacity to accumulate trace elements.

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.

Lead Pb exposure assessment in dried blood spots using Total Reflection X-Ray Fluorescence TXRF

Whole blood remains the most used biomarker for lead (Pb) biomonitoring, however, blood sampling has several limitations, including its invasive nature. Dried Blood Spots (DBS) have been applied as an alternative to traditional methods for decades, but there are gaps that have prevented them to be adopted in biomonitoring programs, such as their small sample volume. There are microanalytical techniques that require a low volume (<10 µL) to perform the analysis, such as Total Reflection X-Ray Fluorescence (TXRF), however, this approach has not been evaluated yet. This study aimed to validate and apply a method to assess Pb exposure using DBS samples and TXRF. First, we developed a method testing different parameters including digestion and extraction procedures, and the use of different internal standards. Next, we validated our method evaluating several validation parameters, and we compared our results with standardized guidelines. Finally, we applied our method with samples from two cohorts. The limits of detection and quantification of the method were 0.28 and 0.69 µg/dL, respectively. The overall precision and accuracy of the method were 14.88 % (9.92-19.14 %) and 111.14 % (97.03-129.70 %), respectively. The Bland-Altman plot indicated a good agreement between ICP-MS and TXRF, with a mean of differences of -0.02 µg/dL. These results demonstrate that TXRF is a good alternative to traditional methods for the analysis of Pb in DBS samples and it alleviates challenges such as the low volume of sample, analytical interferences, and sample throughput.

A road map to assess critical materials content in boron industrial wastes using sustainable micro-X-ray fluorescence and total reflection X-ray fluorescence instrumentation.

Turkey is the leading country in the world in terms of boron production and sale. Increasing boron production goes along with an increasing generation of boron wastes. The pollution of the soil and the air around the waste piles, as well as the occupation of several square kilometers of ground, are major environmental problems. It is, therefore, very important to make use of the wastes to both protect the environment and create revenue. This work presenteda road map for fast screening of boron waste for critical elements followed by determination of the elements using small footprint low power instrumentation. The sample preparation was kept to a minimum. A procedure that allowed an assessment of critical materials in industrial production waste with minimal consumption of hazardous acids, energy, and time was presented. The samples were first screened for valuable and hazardous elements by micro-X-ray fluorescence (XRF). Samples with considerable contents of Cs, Rb, and Aswere then prepared as slurries for the total reflection XRF (TXRF) measurement. To evaluate the TXRF procedure, a standard reference material was analyzed. As a result, Rb and Cs in concentrations up to 420 ± 70 and 1500 ± 200 mg/kg were detected in some of the waste forms. The time savings were in order of a factor of 3 when comparing the prescreening combined micro-XRF and TXRF approach to an all TXRFanalysis approach.

Intravenously administered d-mannitol-coated maghemite nanoparticles cause elemental anomalies in selected rat organs.

In this study novel d-mannitol coated maghemite nanoparticles (MIONPs) are presented in terms of their influence on elemental homeostasis of living organisms and for this purpose highly sensitive total reflection X-ray fluorescence was used. Because of the biological indifference of d-mannitol and presumed lower toxicity of maghemite, compared to the most commonly used magnetite in nanomedicine, such nanoparticles seem to be promising candidates for biomedical applications. The examined dose of MIONPs was comparable with one of the lowest doses used in medical diagnostics. However, it should be emphasized that the amount of iron injected in this form is still significant compared to its total content in organs, especially in kidneys or the heart, and may easily disrupt their elemental homeostasis. The aim of the present study was to evaluate the elemental changes occurring in selected rat organs after injecting a low dose of MIONPs. The results were compared with those obtained for previously examined PEG-coated nanoparticles with magnetite cores. In the light of our findings the elemental changes observed after exposure to MIONPs were less extensive than those following PEG-coated magnetite nanoparticle administration.

INVESTIGATION AND OPTIMIZATION OF COMPLEXATION OF MANGANESE (II) IONS WITH DIHY-DROQUERCETIN IN AQUEOUS SOLUTIONS

The purpose of this work was to study and optimize the complexation reaction of Mn2+ ions with flavonoid dihydroquercetin (DHQ) in aqueous solutions. It was found that the interaction of DHQ (0.015–0.030 M) with manganese (II) salts at molar ratios of DHQ : Mn2+ from 1 : 1 to 1 : 3 at pH 6.9–7.9 leads to the formation of a complex compound (CC) with a stoichiometric ratio of metal : flavonoid ligand (Met : L) 1 : 1. The conditions for the complexation of Mn2+ ions with dihydroquercetin at laboratory conditions optimized for the yield of the product, are proposed. The maximum yield of the complex (95%) was achieved at the interaction of DHQ with Mn(CH3COO)2∙4H2O under conditions: pH 7.7, 70 °C, the reaction time was 15 min, the molar ratio of the initial reagents DHQ: Mn2+ was 1 : 1.5, the initial concentrations were 0.020 M DHQ and 0.030 M Mn2+. The most probable composition of the complex with the determination of the amount of bound water [MnL(OH)(H2O)2] and the structure of the complex were established using the data of thermogravimetry (TG), differential scanning calorimetry (DSC), elemental analysis and X-ray fluorescence analysis (XRF), confirmed by the data of total reflection X-ray fluorescence analysis (TXRF), and EPR spectroscopy data.

Bent crystal Laue analyser combined with total reflection fluorescence X-ray absorption fine structure (BCLA + TRF-XAFS) and its application to surface studies.

A bent crystal Laue analyser (BCLA) is an X-ray energy analyser used for fluorescence X-ray absorption fine-structure (XAFS) spectroscopy to separate the fluorescence X-ray emission line of a target atom from the elastic scattering X-rays and other fluorescence emission lines. Here, the feasibility of the BCLA for total reflection fluorescence XAFS (TRF-XAFS), which has a long X-ray footprint on the substrate surface owing to grazing incidence, was tested. The focal line of the BCLA was adjusted on the X-ray footprint and the XAFS signal for one monolayer of Pt deposited on a 60 nm Au film with high sensitivity was obtained. Although range-extended XAFS was expected by the rejection of Au fluorescence arising from the Au substrate, a small glitch was found in the Au L3 edge because of the sudden change of the complex refraction index of the Au substrate at the Au edge. This abnormal spectrum feature can be removed by reflectivity correction using Au foil absorption data. BCLA combined with TRF-XAFS spectroscopy (BCLA + TRF-XAFS) is a new technique for the in situ surface analysis of highly dispersed systems even in the presence of a liquid overlayer.

Suspension assisted analysis of sulfur in petroleum coke by total-reflection X-ray fluorescence

The influence of the particle size distribution of a petroleum coke sample compared to its sulfur content was investigated. For this matrix, an optimization procedure of the Suspension Assisted Analysis (SAA) by Total-reflection X-Ray Fluorescence (TXRF) quantitative method was developed. SAA-TXRF sulfur recoveries were evaluated for three particle size distributions of the same coke sample. The sulfur recovery increased when the particle size distribution was smaller. The observed behaviour was correlated and validated with CHNS elemental analysis and microwave-assisted digestion TXRF measurements. The results indicate that the sulfur signal is strongly influenced by the particle size distribution and the deposition morphology of the petroleum coke material. This effect could be explained by the presence of a strong absorption effect for the sulfur signal in combination with the distortion of the X-ray Standing Waves (XSW) field observed between the analyte, S, and the elements Ti and Co, which were used as an internal standard. The variation in sulfur observed was up to 45.5% lower than the higher recovery obtained by CHNS. This investigation suggests that for an adequate application of the SAA-TXRF method in petroleum coke or similar matrices, careful optimization of the final particle dispersion of the ground coke is crucial and necessary. In this case, the use of a high- power ultrasound probe was the key.

Relationship of levels of trace elements in saliva and dental caries in preschool children using total reflection X-ray fluorescence technique (TXRF)⋆

BackgroundConsidering that studies on the relationship between dental caries and trace elements present contradictory and inconclusive results, the purpose of this study was to determine the levels of salivary trace elements in saliva samples of preschool children and investigate their relationship with dental caries. MethodsIn total, 120 samples of unstimulated saliva were collected from children aged 36–72 months, of both sexes, who participate in the preventative educational program in oral health at the State University of Londrina, Brazil. The children were divided into two groups, caries (n = 60) and non-caries (n = 60). Levels of Al, Cu, Fe, Mn, and Zn were analyzed by total reflection X-ray fluorescence (TXRF). Descriptive statistics, the Student’s t-test, Mann-Whitney U test, and Pearson’s Chi-squared test were performed (P < 0.05). ResultsThe concentrations of Mn and Fe were significantly higher in the caries group (Mn =0.015 mg/L [0.007−0.020]; Fe =0.080 mg/L [0.031−0.239] than the non-caries group (Mn =0.010 mg/L [0.001 – 0.017]; Fe =0.044 mg/L [0.023 – 0.107]). ConclusionThe results suggest a relationship between trace elements and dental caries, indicating possible involvement of these elements in the metabolism of microorganisms involved in the carious process. In addition, the use of TXRF presented satisfactory results, with a simple and fast methodology for the detection of the studied elements.

Influence of Conventional or Invisalign Orthodontic Treatment on Mineral and Trace Element Salivary Levels: Longitudinal Study with Total Reflection X-ray Fluorescence.

This work aimed to evaluate the salivary concentration of chemical elements in patients undergoing orthodontic treatment with fixed orthodontic appliances and removable aligners. Twelve Angle Class I and II orthodontic patients undergoing treatment with conventional fixed appliances and 15 patients treated with removable aligners provided unstimulated whole saliva samples before treatment (pre) and after 3 months of treatment (post). The concentration and secretion rate of chemical elements in saliva were determined by total reflection X-ray fluorescence. Differences from pre to post and between groups were determined with the paired T test or Wilcoxon test, and two-way ANOVA, considering P < 0.05. The concentrations of S, Cl, and K decreased, while Zn increased significantly (P < 0.05) between pre and post treatment with the fixed appliance treatment. The salivary secretion rate of S was decreased from pre to post in the fixed appliance group. No differences in the concentration and secretion rate of chemical elements were detected from pre to post in the Invisalign group. Fe secretion rate presented an interaction between time and treatment, with lower secretion at post (P = 0.02) in the Invisalign group. Increased Br secretion rate and decreased Rb, Fe, P, and K in Invisalign patients suggested a better salivary electrolyte profile regarding periodontal bone remodeling. No significant alterations in ions associated with metal corrosion and inflammatory reactions were detected in orthodontic patients under dental plaque control.

Total reflection X-ray fluorescence analysis of uranium in the presence of competing elements☆

The analysis of uranium in environmental samples, quantified using total reflection X-ray fluorescence (TXRF) analysis, would be adversely affected by the presence of rubidium and strontium in larger amounts than uranium as coexisting elements. This is because the U Lα line at 13.61 keV is close to the Rb Kα line at 13.40 keV and the Sr Kα line at 14.17 keV. Using the U Lβ1 line (instead of the U Lα line), which does not overlap with the peaks of coexisting elements, we will be able to avoid these adverse effects. Since there is no TXRF device that can perform a quantitative analysis of uranium by using the U Lβ1 line, the following modifications were made to the existing device with the intention of rapid on-site analysis. The X-ray tube of the new device has a silver anode instead of a tungsten anode, and the sensitive area of the detector was expanded. In addition, the mechanism for adjusting the position of the sample stage was changed from manual to computerized control. These changes made it possible to screen uranium in environmental samples rapidly on site without chemical separation.

Application of TXRF in monitoring trace metals in particulate matter and cloud water

Abstract. Trace metals in ambient particulate matter and cloud are considered key elements of atmospheric processes as they affect air quality, environmental ecosystems, and cloud formation. However, they are often available at trace concentrations in these media such that their analysis requires high-precision and sensitive techniques. In this study, different analytical methods were applied to quantify trace metals in particulate matter (PM) samples collected on quartz and polycarbonate filters as well as cloud water, using the Total reflection X-Ray Fluorescence (TXRF) technique. These methods considered the measurement of filter samples directly without and with chemical pretreatment. Direct measurements involved the analysis of PM samples collected on polycarbonate filters and cloud water samples after they are brought onto TXRF carrier substrates. The chemical treatment method involved the assessment of different acid digestion procedures on PM sampled on quartz filters. The solutions applied were reverse aqua regia, nitric acid, and a combination of nitric acid and hydrogen peroxide. The effect of cold-plasma treatment of samples on polycarbonate filters before TXRF measurements was also investigated. Digestion with the reverse aqua regia solution provided lower blanks and higher recovery in comparison to other tested procedures. The detection limits of the elements ranged from 0.3 to 44 ng cm−2. Ca, K, Zn, and Fe showed the highest detection limits of 44, 35, 6, and 1 ng cm−2, while As and Se had the lowest of 0.3 and 0.8 ng cm−2, respectively. The method showed higher recovery for most trace metals when applied to commercially available reference materials and field samples. TXRF measurements showed good agreement with results obtained from ion chromatography measurements for elements such as Ca and K. Cold-plasma treatment did not significantly lead to an increase in the detected concentration, and the results were element specific. Baking of the quartz filters prior to sampling showed a reduction of more than 20 % of the filter blanks for elements such as V, Sr, Mn, Zn, and Sb. The methods were applied successfully on ambient particulate matter and cloud water samples collected from the Atlas Mohammed V station in Morocco and the Cape Verde Atmospheric Observatory. The obtained concentrations were within the range reported using different techniques from similar remote and background regions elsewhere, especially for elements of anthropogenic origins such as V, Pb, and Zn with concentrations of up to 10, 19, and 28 ng m−3, respectively. Enrichment factor analysis indicated that crustal matter dominated the abundance of most of the elements, while anthropogenic activities also contributed to the abundance of elements such as Sb, Se, and Pb. The results confirm that TXRF is a useful complementary sensitive technique for trace metal analysis of particulate matter in the microgram range as well as in cloud water droplets.

Feasibility study of elemental analysis of large population of formalin fixed paraffin embedded tissue samples – preliminary results

The goal of this study was to check the repeatability of changes of elemental composition of tissues introduced by formalin fixation followed by paraffin embedding (FFPE) – standard processing protocol used in histopathology. To achieve that goal two series of ten samples of quasi-homogeneous swine liver samples – lyophilised and FFPE processed – were compared in terms of statistical dispersion of their elemental concentrations. Total Reflection X-Ray Fluorescence (TXRF) was used for quantification of K, Ca, Mn, Fe, Cu, Zn, Se Br, Rb and Sr in samples after their acid digestion. It has been shown that relative standard deviation introduced by the statistical dispersion of the FFPE processing typically does not exceed 30% which may open up the possibility of analysis of large population of archival tissues.

Development of a Portable XRF Spectrometer and Its Application

We have developed 2 kinds of portable XRF spectrometers for on-site analysis. The first is equipped with a monochromator, making it possible to sensitively analyze under a low background. This equipment is used widely in the archaeology field and an industrial field. Recently, we also developed equipment that improved the analysis sensitivity of the light element.Another equipment is a portable total reflection X-ray fluorescence (TXRF) spectrometer. We developed this equipment using polychromatic X-rays from an X-ray source of single-digit Watt. It has an analysis sensitivity of pg order. This equipment is used in the environment field, biological samples and in the analysis of uranium from nuclear power plants. This report, introduces an outline and application examples about 2 kinds of portable XRF spectrometers.

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

Direct non-destructive total reflection X-ray fluorescence elemental determinations in zirconium alloy samples.

The development of a direct non-destructive synchrotron-radiation-based total reflection X-ray fluorescence (TXRF) analytical methodology for elemental determinations in zirconium alloy samples is reported for the first time. Discs, of diameter 30 mm and about 1.6 mm thickness, of the zirconium alloys Zr-2.5%Nb and Zircalloy-4 were cut from plates of these alloys and mirror polished. These specimens were presented for TXRF measurements directly after polishing and cleaning. The TXRF measurements were made at the XRF beamline at Elettra synchrotron light source, Trieste, Italy, at two different excitation energies, 1.9 keV and 14 keV, for the determinations of low- and high-Z elements, respectively. The developed analytical methodology involves two complementary quantification schemes, i.e. using either the fundamental parameter method or relative sensitivity based method, allowing quantification of fifteen minor and trace elements with respect to Zr with very good precision and accuracy. In order to countercheck the TXRF analytical results, some samples were analyzed using the DC arc carrier distillation atomic emission spectrometry technique also, which shows an excellent agreement with the results of the TXRF-based methodology developed in this work. The present work resulted in a non-destructive TXRF elemental characterization methodology of metal and alloy samples avoiding the cumbersome dissolution and matrix separation which arenormally required in other techniques and traditional methods of TXRF determination. In addition, the production of analytical waste could also be avoided to a large extent. Although the work was carried out for specific applications in the nuclear industry, it is equally suitable for other such samples in different industrial applications.

Multivariate probing of antitumor metal-based complexes damage on living cells through Raman imaging.

Intracellular modifications caused by two metal-based antitumor compounds were assessed by confocal Raman imaging assisted by multivariate curve resolution method, a very powerful deconvolution tool that can be used to extract the characteristic spectral profile of the individual or "purest" components from an image dataset. The use of this Raman methodology has the advantage of being non-invasive and totally label-free. Four main different intracellular processes were observed under the Raman imaging and multivariate approach combination, and even, significant differences could be identified between the treatments with both metallodrugs. Leakage of the nucleus and nucleolus content into the cytoplasm, along with releasing of cytochrome c were observed for the treatment with the Cu-based complex. At the same time, changes of hydrogen-bonding network were also evidenced, indicating an apoptotic cellular death process, consistent with complementary Total Reflection X-Ray fluorescence (TXRF) and fluorescence experiments attesting mitochondria and DNA as main targets after uptake of the complex by cells. For treatment with the Zn-based complex, changes associated with cytochrome c were not detected, neither a rapid leakage of nucleus content upon 24 h treatment. The hydrogen-bonding network also followed a quite different pattern, suggesting that with this metallodrug, the cellular death follows a different mechanism.