Total Reflection X-ray Spectrometry Research Articles

Elemental analysis of valuable byproducts by TXRF spectrometry: coal fly ash and activated carbon

In order to ensure that byproducts are environmentally friendly and fit for purpose, their chemical composition must be determined, with special attention to elements at trace level. The large variability in the type of matrices demands a versatile analytical technique, compatible with sample preparation methods allowing both fast composition screenings and accurate quantitative analysis.In this work, byproducts derived from carbon-rich matrices, including coal fly ash and activated carbon from coconut and almond shells, were investigated by means of total reflection x-ray spectrometry and different sample preparations. Suspension, acid digestion, solid-liquid extraction and ashing were performed and assessed as to their complexity and detection capabilities, ranging from 0.01 mg/kg to 16 mg/kg, depending on the element and sample preparation. The internal standard quantification with gallium, aided by a variation of the standard additions method to take into account its possible presence in the samples, allowed to determine elements of environmental and technological interest, including K, Ca, Ti, V, Mn, Cr, Ni, Cu, Zn, Ga, As, Sr, Pb. Assets, limits and possible developments are presented and discussed.

Metals quantification in e-cigarettes liquids by Total Reflection X-ray Spectrometry

Electronic cigarettes (e-cig) have gained popularity around the world and its health risks demands more research. This study aims at characterizing e-cig liquids (e-liquids) and its constituents by Total Reflection X-ray Spectrometry (TXRF). The internal standard method was the quantification procedure employed. The spectrometer's performance was evaluated with one certified reference material and spiked samples. It was possible to quantify K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, and Pb in the e-liquids. Concentrations above the limit for potable water were found in 10 out of 38 samples. Principal component analysis was useful for identifying toxic samples. TXRF is a promising technique for e-liquids evaluation due to its simplicity and performance.

Simple method for Cr(VI) determination by liquid-liquid microextraction combined with total reflection X-ray fluorescence spectrometry: Application to water samples and industrial extracts

In the present contribution, a simple and inexpensive method for the determination of hexavalent chromium in aqueous solutions was developed. The analytical methodology consists of the combined use of a low cost Cr(VI) isolation procedure followed by the analysis using total reflection X-ray spectrometry (TXRF). The liquid-liquid microextraction procedure (LLME) used is based on the formation of an ion-pair between the cationic part of the surfactant cetyltrimethylammonium bromide (CTAB) and the corresponding anionic Cr(VI) species, which is extracted in few microliters of chloroform. TXRF analysis can be performed directly by deposition of 15 μL of the preconcentrated sample on a sample carrier, without any additional sample treatment.Experimental parameters affecting Cr(VI) extraction and TXRF analysis were studied in detail. Under optimum conditions, a good linearity was obtained in the range of 5–5000 μg/L with a limit of detection for hexavalent chromium of 0.9 μg/L. This fact opens the possibility of Cr determination in aqueous samples characterized by different concentration levels. The methodology was successfully applied for the determination of Cr(VI) species in different type of water matrices (tap, well, river and sea water) as well as industrial aqueous samples including in industrial waste water from a galvanic industry and aqueous clinker extracts. For comparison purposes, the determination of Cr(VI) in industrial samples was also carried out by using the colorimetric method EPA Method 7196.

Total reflection X-ray spectroscopy based detection of uranium and thorium in phosphogypsum simulated by Monte Carlo method

Detection of trace amounts of uranium and thorium in phosphogypsum using total reflection X-ray fluorescence (TXRF) was addressed by Monte Carlo method (MCNP code, version 6.2). The simulated samples contained average concentrations of 238U (120 Bq/kg) and 232Th (40 Bq/kg), as well as 7 major components in oxide forms and other 11 heavy metals in trace amounts, commonly found in PG. It was found that, for a molybdenum target X-ray tube operating under total reflection condition and equipped with an SDD detector, the detection limit for uranium and thorium in the simulated multi-elemental sample are (1.42±0.04)ng and (1.03±0.02)ng, respectively. Based on parameters of certified solutions for uranium and thorium, and adding gallium as an internal standard element, calibration plots provided mass recovery from the multi-component sample with relative errors of 4.56% for uranium and 2.74% for thorium. Our results show that TXRF technique can accurately detect and quantify trace amounts of uranium and thorium in the presence of matrix effects without any pre-treatment of PG samples.

A surface sensitive hard X-ray spectroscopic method applied to observe the surface layer reduction reaction of Co oxide to Co metal.

A simple and easy surface sensitive spectroscopic method using hard X-rays has been developed and applied to observe the surface oxide reduction reaction. The method named TREXS, Total REflection X-ray Spectroscopy, records the total reflection of incident X-rays at sample surfaces. The surface reduction reaction of Co oxide (Co3O4) to Co metal was successfully observed by in situ TREXS measurements with a surface sensitivity of ∼2 nm. The in situ TREXS measurements were performed under H2 flow of N2 balanced atmospheric pressure with increasing temperature. This method, in situ TREXS, will be a suitable and powerful tool to observe a variety of surface chemical reactions and consequently to understand catalytic processes under realistic operating conditions.

In situ TREXS Observation of Surface Reduction Reaction of NiO Film with ∼2 nm Surface Sensitivity.

X-ray absorption fine structure (XAFS) spectroscopy is one of the most widely used methods at synchrotron radiation facilities. XAFS gives us information on chemical states and local structures. Fundamentally, XAFS is bulk sensitive, not surface sensitive. If a surface sensitive XAFS method was available, surface chemical reactions can be observed under realistic conditions. Here, we report the development and present status of a type of surface sensitive x-ray spectroscopy, which is named total reflection x-ray spectroscopy, TREXS.

Total reflection X-ray spectroscopy as a rapid analytical method for uranium determination in drainage water

ABSTRACTUranium concentrations in drainage water are typically determined by α-spectrometry. However, due to the low specific radioactivity of uranium, the evaporation of large volumes of drainage water, followed by several hours of measurements, is required. Thus, the development of a rapid and simple detection method for uranium in drainage water would enhance the operation efficiency of radiation control workers. We herein propose a novel methodology based on total reflection X-ray fluorescence (TXRF) for the measurement of uranium in contaminated water. TXRF is a particularly desirable method for the rapid and simple evaluation of uranium in contaminated water, as chemical pretreatment of the sample solution is not necessary, measurement times are typically several seconds, and the required sample volume is low. We herein employed sample solutions containing several different concentrations of uranyl acetate with yttrium as an internal standard. The solutions were placed onto sample holders, and were dried prior to TXRF measurements. The relative intensity, otherwise defined as the net intensity ratio of the Lα peak of uranium to the Kα peak of yttrium, was directly proportional to the uranium concentration. Using this method, a TXRF detection limit for uranium in contaminated water of 0.30 µg/g was achieved.

Observation of surface reduction of NiO to Ni by surface-sensitive total reflection X-ray spectroscopy using Kramers–Kronig relations

We have developed a promising surface-sensitive X-ray absorption fine structure (XAFS) measurement method. This method is based on total reflection detection and Kramers–Kronig relations, and has been named the KK-XAFS method. Total reflection spectra are transformed via Kramers–Kronig relations to obtain XAFS spectra. KK-XAFS experiments give us surface-sensitive structural parameters, while usual EXAFS analyses yield bulk structural parameters. The total reflection spectra themselves are useful for observing and discussing time evolutions of chemical reactions at surfaces by quick scanning measurements. Chemical species are analyzed to estimate their fractions during reactions. The whole method would be named total reflection X-ray spectroscopy (TREXS). A reduction of the NiO layer at the surface of Ni (30 nm)/Si was observed in a laboratory-built TREXS in situ cell. The method would be applicable to observe chemical reactions starting at surfaces and to study their kinetics and mechanisms.

Iron overload of human colon adenocarcinoma cells studied by synchrotron-based X-ray techniques.

Fast- and slow-proliferating human adenocarcinoma colorectal cells, HT-29 and HCA-7, respectively, overloaded with transferrin (Tf), Fe(III) citrate, Fe(III) chloride and Fe(II) sulfate were studied by synchrotron radiation total-reflection X-ray spectrometry (TXRF), TXRF-X-ray absorption near edge structure (TXRF-XANES), and micro-X-ray fluorescence imaging to obtain information on the intracellular storage of overloaded iron (Fe). The determined TfR1 mRNA expression for the investigated cells correlated with their proliferation rate. In all cases, the Fe XANES of cells overloaded with inorganic Fe was found to be similar to that of deliquescent Fe(III) sulfate characterized by a distorted octahedral geometry. A fitting model using a linear combination of the XANES of Tf and deliquescent Fe(III) sulfate allowed to explain the near edge structure recorded for HT-29 cells indicating that cellular overload with inorganic Fe results in a non-ferritin-like fast Fe storage. Hierarchical cluster analysis of XANES spectra recorded for Fe overloaded HT-29 and HCA-7 cells was able to distinguish between Fe treatments performed with different Fe species with a 95% hit rate, indicating clear differences in the Fe storage system. Micro-X-ray fluorescence imaging of Fe overloaded HT-29 cells revealed that Fe is primarily located in the cytosol of the cells. By characterizing the cellular Fe uptake, Fe/S content ratios were calculated based on the X-ray fluorescence signals of the analytes. These Fe/S ratios were dramatically lower for HCA-7 treated with organic Fe(III) treatments suggesting dissimilarities from the Tf-like Fe uptake.

Analytical capabilities of two-phase hollow-fiber liquid phase microextraction for trace multielement determination in aqueous samples by means of portable total reflection X-ray instrumentation

Liquid phase microextraction (LPME) procedures have been widely used in combination with atomic and emission spectroscopic techniques for the isolation and preconcentration of trace elements. However, its application in combination with total reflection X-ray spectrometry (TXRF) is still scarce. In this paper, we evaluate the possibilities and drawbacks of a two-phase hollow fiber LPME procedure in combination with TXRF for the simultaneous determination of trace amounts of Cr, Ni, Cu, Zn, Pb, and Cd in aqueous samples. After extraction of the analytes by using the optimum conditions (sample volume: 25 mL, complexing agent: APDC, organic solvent: hexylbenzene, extraction time: 2 h, extraction speed: 660 rpm), 10 $\mu $L of the preconcentrated sample was deposited on a preheated quartz reflector, dried on a hot plate at 80 $^{\circ}$C, and analyzed by TXRF. Using such conditions, limits of detection lower than 3 $\mu $g L$^{-1}$ were obtained for all metals. In spite of LODs improvement in comparison with the direct analysis of the aqueous samples (up to a factor of 100), precision of the results was not optimal (RSD$\sim $20%). This fact may be related to the use of a low volatility solvent as extractant phase that hampers the later TXRF analysis.

Analysis of Trace Elements in Groundwater Using ICP-OES and TXRF Techniques and Its Compliance with Brazilian Protection Standards

In this work, an assessment of groundwater quality and its compliance with Brazilian environmental protection standards was carried out. Ground waters from the Serra Geral aquifer are currently used for human consumption at the western region of the Brazilian state of Parana. Ground water samples from 10 wells covering the entire Toledo municipality rural region were collected and analysed by two highly accurate and sensitive spectrometric techniques: inductively coupled plasma–optical emission spectrometry (ICP-OES) and total reflection X-ray spectrometry (TXRF). Among all detected elements, 18 elements (As, Ba, Br, Ca, Pb, Cl, Co, Cu, Cr, Fe, P, S, Mn, Ni, K, Ti, V and Zn) were measured by the TXRF technique while three elements (B, Mg and Na) were measured by ICP-OES. Trace element concentration levels were then compared with Brazilian environmental legislation (BEL). From the results obtained, concentrations of chromium, iron, arsenic, selenium, manganese and barium were detectable in some wells at slightly above the maximum limits allowed by the BEL.

Total reflection X-ray spectrometry (TXRF) for trace elements assessment in edible clams.

The present contribution presents a preliminary investigation of the chemical composition with respect to major, minor, trace, and ultratrace elements in several clam species that are frequently used for human consumption in Portuguese markets and worldwide. In order to use a simple and rapid analytical methodology for clam analysis, energy dispersive X-ray fluorescence (EDXRF) spectrometry and total reflection X-ray fluorescence (TXRF) spectrometry were selected as analytical techniques. The analytical capabilities of TXRF spectrometry were evaluated for the determination of minor and trace elements in commercial edible clams. We compared the direct analysis of powdered suspensions (using different sample amounts and dispersant agents) with the analysis of the digested samples for trace element determination. Inductively coupled plasma mass spectrometry analysis of clam digests was also performed to evaluate the analytical possibilities of TXRF spectrometry for trace and ultratrace analysis.

Feasibility study of total reflection X-ray fluorescence analysis using a liquid metal jet X-ray tube

Total reflection X-ray spectroscopy (TXRF) is a powerful analytical technique for qualitative and quantitative analysis of trace and ultratrace elements in a sample with lower limits of detection (LLDs) of pg/g to ng/g in concentration and absolute high fg levels are attainable. Several X-ray sources, from low power (few W), 18kW rotating anodes to synchrotron radiation, are in use for the excitation and lead accordingly to their photon flux delivered on the sample the detection limits specified. Not only the power, but also the brilliance and focal shape are of importance for TXRF. A microfocus of 50–100μm spot size or the line focus of diffraction tubes is best suited. Excillum developed a new approach in the design of a source: the liquid metal jet anode. In this paper the results achieved with this source are described. A versatile TXRF spectrometer with vacuum chamber designed at Atominstitut was used for the experiments. A multilayer monochromator selecting the intensive Ga-Kα radiation was taken and the beam was collimated by 50μm slits. Excellent results regarding geometric beam stability, high fluorescence intensities and low background were achieved leading to detection limits in the high fg range for Ni. A 100mm2 silicon drift detector (SDD) collimated to 80mm2 was used to collect the fluorescence radiation. The results from measurements on single element samples are presented.

Ultrasonic slurry sampling combined with total reflection X-ray spectrometry for multi-elemental analysis of coastal sediments in a ria system

An increased concern on environmental issues has arisen in recent decades. Human activities have a great impact on the environment, efficient methodologies being needed for quick assessment of possible contamination sources and their effects. This paper describes a fast method for analysis of sediments by Total Reflection X-ray Fluorescence (TXRF) using a simple and rapid sample preparation approach, i.e., Ultrasonic Probe Slurry Sampling (UPSS), as an alternative to digestion. UPSS involves minimal consumption of sample and reagents within the range of microanalysis. A case study focused on a coastal area (Ria of Arousa, NW Spain) is presented. The simultaneous determination of 10 elements (Ti, V, Mn, Fe, Cu, Zn, As, Rb, Sr and Pb) was accomplished by UPSS-TXRF. Method validation was performed by means of several certified reference materials. Distribution patterns, natural background levels and enrichment factors that are indicative of contamination were obtained. Application of principal component analysis (PCA) allowed assessing the origin of trace metals in sediments of the Ria of Arousa.

Determination of platinum group metal catalyst residues in active pharmaceutical ingredients by means of total reflection X-ray spectrometry

The control of metal catalyst residues (i.e., platinum group metals (PGMs)) in different stages of the manufacturing processes of the active pharmaceutical ingredients (APIs) and, especially, in the final product is crucial. For API specimens, there are strict guidelines to limit the levels of metal residues based on their individual levels of safety concern. For PGMs the concentration limit has been established at 10mg/kg in the API.Therefore great effort is currently being devoted to the development of new and simple procedures to control metals in pharmaceuticals.In the present work, an analytical methodology based on benchtop total reflection X-ray fluorescence spectrometry (TXRF) has been developed for the rapid and simple determination of some PGM catalyst impurities (Rh, Pd, Ir and Pt) in different types of API samples. An evaluation of different sample treatments (dissolution and digestion of the solid pharmaceutical samples) has been carried out and the developed methodologies have been validated according to the analytical parameters to be considered and acceptance criteria for PGM determination according to the United States Pharmacopeia (USP). Limits of quantification obtained for PGM metals were in the range of 2–4mg/kg which are satisfactory according to current legislation. From the obtained results it is shown that the developed TXRF method can be implemented in the pharmaceutical industries to increase productivity of the laboratory; offering an interesting and complementary analytical tool to other atomic spectroscopic methods.

Liquid phase microextraction strategies combined with total reflection X-ray spectrometry for the determination of low amounts of inorganic antimony species in waters

In the present study, and taking into account the microanalytical capability of total reflection X-ray spectrometry (TXRF), we explored the possibilities of hollow fibre liquid-phase microextraction (HF-LPME) and dispersive liquid–liquid microextraction (DLLME) combined with TXRF for the determination of low amounts of inorganic Sb species in waters.For each of the LPME configurations aforementioned, experimental parameters affecting Sb extraction but specially the proper sample preparation process (deposition volume on the reflective carrier and drying mode) and measurement conditions for subsequent TXRF analysis have been carefully evaluated.The best analytical strategy for the determination of Sb(III) and Sb(V) in the low μgL−1 range was found to be the application of the DLLME mode before TXRF analysis. The developed methodology was successfully applied to the determination of inorganic Sb speciation in different types of spiked water samples.

TRA-1-60+, SSEA-4+, POU5F1+, SOX2+, NANOG+ Clones of Pluripotent Stem Cells in the Embryonal Carcinomas of the Testes

Cancer of the testes is currently the most frequent neoplasm and a leading cause of morbidity in men 15-35 years of age. Its incidence is increasing. Embryonal carcinoma is its most malignant form, which either may be resistant or may develop resistance to therapies, which results in relapses. Cancer stem cells are hypothesized to be drivers of these phenomena. The specific aim of this work was identification and isolation of spectra of single, living cancer stem cells, which were acquired directly from the patients' biopsies, followed by testing of their pluripotency. Biopsies were obtained from the patients with the clinical and histological diagnoses of the primary, pure embryonal carcinomas of the testes. The magnetic and fluorescent antibodies were genetically engineered. The SSEA-4 and TRA-1-60 cell surface display was analyzed by multiphoton fluorescence spectroscopy (MPFS), flow cytometry (FCM), immunoblotting (IB), nuclear magnetic resonance spectroscopy (NMRS), energy dispersive x-ray spectroscopy (EDXS), and total reflection x-ray spectroscopy (TRXFS). The single, living cells were isolated by magnetic or fluorescent sorting followed by their clonal expansion. The OCT4A, SOX2, and NANOG genes' transcripts were analyzed by qRTPCR and the products by IB and MPFS. The clones of cells, with the strong surface display of TRA-1-60 and SSEA-4, were identified and isolated directly from the biopsies acquired from the patients diagnosed with the pure embryonal carcinomas of the testes. These cells demonstrated high levels of transcription and translation of the pluripotency genes: OCT4A, SOX2, and NANOG. They formed embryoid bodies, which differentiated into ectoderm, mesoderm, and endoderm. In the pure embryonal carcinomas of the testes, acquired directly from the patients, we identified, isolated with high viability and selectivity, and profiled the clones of the pluripotent stem cells. These results may help in explaining therapy-resistance and relapses of these neoplasms, as well as, in designing targeted, personalized therapy.

Determination of cadmium at ultratrace levels in environmental water samples by means of total reflection X-ray spectrometry after dispersive liquid–liquid microextraction

Until now, the determination of Cd at trace levels in aqueous samples by TXRF has been restricted. When Mo-target X-ray tubes are used, low sensitivity and interferences with Cd L-lines used for quantification prevent trace analysis. Alternatively, when W-target X-ray tubes are used Cd excitation is limited. For this reason, a sample pretreatment is usually necessary to extract, isolate and concentrate Cd prior to TXRF analysis. In the present contribution, the feasibility of a dispersive liquid-liquid microextraction approach (DLLME) combined with TXRF for ultratrace Cd determination in different types of environmental waters is shown. Parameters affecting the extraction procedure and TXRF measurement conditions have been carefully evaluated to ensure the highest sensitivity for Cd determination. Using the best analytical conditions, it was found that the minimum cadmium content that could be detected in an aqueous solution was 0.04 μg L−1. This value is more than two orders of magnitude lower compared with the direct TXRF analysis of Cd in aqueous samples. The precision of the methodology was evaluated in terms of relative standard deviation (RSD) of six replicate analyses of a standard solution containing 3 μg L−1. The precision of the method was determined to be approximately 5% RSD. In order to test the suitability of the method when dealing with complex matrices as well as the influence of interfering ions, the determination of Cd in spiked water samples (sea water, estuarine water and river water) at the levels of 1 μg L−1 and 5 μg L−1 was undertaken and Cd added to the samples was quantitatively determined. Our results give insight into the possibilities of the combination of DLLME and TXRF for ultratrace Cd determination in different types of environmental waters.

Total reflection X-ray fluorescence spectrometry as a tool for the quantification of gold and platinum metallodrugs: Determination of recovery rates and precision in the ppb concentration range

Total reflection X-ray spectrometry is an instrumental technique based on X-ray fluorescence, which offers detection limits low enough to quantify trace element concentrations with negligible interference from matrix components. The technique is well established in material sciences and now reaches out to extended applications in life sciences and pharmaceutical quality control. In our study we focused on possible applications for the quantification of gold and platinum containing active ingredients in trace concentrations (ppb range) in a matrix of biological origin (cell suspensions). General aspects of sample preparation as well as selected important method performance parameters (precision, recovery rates) were investigated. Overall, TXRF represents an useful option to quantify metals in ppb concentrations with acceptable precision and recovery.

TRA-1-60+, SSEA-4+, Oct4A+, Nanog+ Clones of Pluripotent Stem Cells in the Embryonal Carcinomas of the Ovaries

Embryonal carcinoma of the ovary (ECO), pure or admixed to other tumors, is the deadly gynecological cancer. The specific aim of this work was identification, isolation, clonal expansion, and molecular profiling of the pluripotent cells in the embryonal carcinomas of the ovaries. The samples were acquired from the patients, who were clinically and histopathologically diagnosed with the advanced, pure embryonal carcinomas of the ovaries. The cell surface display of the TRA-1-60 and SSEA-4 was analyzed by flow cytometry (FCM), immunoblotting (IB), multiphoton fluorescence spectroscopy (MPFS), nuclear magnetic resonance spectroscopy (NMRS), and total reflection x-ray spectroscopy (TRXFS). The transcripts of the Oct4A and Nanog were analyzed by qRTPCR and MPFS and the products by MPFS. The human pluripotent, embryonic stem cells (ESC), human pluripotent, embryonal carcinoma of the testes (ECT), healthy tissues of the ovary (HTO), healthy tissue of testes (HTT), peripheral blood mononuclear cells (PBMC), and bone marrow mononuclear cells (BMMC) served as the controls. The studied embryonal carcinomas of the ovaries (ECOs) contained the cells with the strong surface display of the TRA-1-60 and SSEA-4, which was similar to the pluripotent ESC and ECT. Their morphology was consistent with the histopathological diagnosis. Moreover, these cells showed strong expression of the Oct4A and Nanog, which was similar to the pluripotent ESC and ECT. The ECO cells formed embryoid bodies, which differentiated into ectoderm, mesoderm, and endoderm. These cells were induced to differentiate into muscles, epithelia, and neurons. Herein, we revealed presence and identified molecular profiles of the clones of the pluripotent stem cells in the embryonal carcinomas of the ovaries. These results should help us with refining molecular diagnoses of these deadly neoplasms and design biomarker-targeted, patient-centered, personalized therapy.