Total Reflection X-ray Fluorescence Spectrometry Research Articles

Evaluation of distribution and bioavailability of Cr, Mn, Fe, Cu, Zn and Pb in the waters of the upper course of the Lerma River

AbstractDistribution and bioavailability of Cr, Mn, Fe, Cu, Zn, and Pb in the waters of the upper course of the Lerma River (UCLR), Mexico, were evaluated by means total reflection x‐ray fluorescence spectrometry. The surface water samples were collected from eight sites distributed along the flow direction of the river. Four sampling campaigns were carried out in each site during a one‐year period. The water samples were analyzed in triplicate, using a TXRF Spectrometer ‘TX‐2000 Ital Structures’ with a Si(Li) detector and a resolution of 140 eV (FWHM) at Mn Kα. A Mo tube (40 kV, 30 mA) with 17.4 KeV excitation energy was used for a counting time of 500 s. Results show that the concentration ranges of heavy metals in the water are the following: Cr, from < 5 to 56 µg/l; Mn, from 9 to 788 µg/l; Fe, from 98 to 8474 µg/l; Cu, from 10 to 225 µg/l; Zn, from 23 to 189 µg/l and Pb, from < 3 to 30 µg/l. There are significant statistical differences in the concentration of heavy metals between the different sampling sites and between the different sampling campaigns. The Pearson correlation results indicate a strong correlation between some heavy metals in the water, this significant correlation (p < 0.05) indicating a natural or/and a shared contamination source for these metals. Metal concentration in the water mostly did not exceed the guide values given by Mexican regulation for agricultural use. Only Cu, Mn and Fe in total water phase exceeded the maximum permissible limits for irrigation proposes at some sites. Copyright © 2007 John Wiley & Sons, Ltd.

Study of archaeological ceramics by total-reflection X-ray fluorescence spectrometry: Semi-quantitative approach

Total-reflection X-ray fluorescence spectrometry has been compared with Instrumental Neutron Activation Analysis in order to test its potential application to the study of archaeological ceramics in the archaeometric field. Two direct solid non-chemical sample preparation procedures have been checked: solid sedimentation and solid chemical homogenization. For sedimentation procedure, total-reflection X-ray fluorescence allows the analysis of the elemental composition with respect to the size fraction but not the average evaluation of the composition. For solid chemical homogenization procedure, total-reflection X-ray fluorescence provides precise (from 0.8% to 27% of coefficient of variation) and accurate results (from 91% to 110% of recovery) for 15 elements (Cr, Hf, Ni, Rb, Al, Ba, Ca, K, Mn, Ti, V, Cu, Ga, Y and Fe) with an easy sample preparation process of the solid clay and without previous chemical treatment. The influence of the particle sizes has been checked by total-reflection X-ray fluorescence sample angle scans and anomalous behaviors have been found for three additional detected elements: As, Sr and Zn, which can be attributed to interference effects of the mineral grain sizes of their associated chemical phases in the total-reflection X-ray fluorescence interference region. The solid chemical homogenization procedure produces data useful for archaeological interpretation, which is briefly illustrated by a case-study. Finally, the decantation procedure data can be also useful for size chemical speciation and, consequently, for alternative environmental total-reflection X-ray fluorescence applications.

Analytical performance of different X-ray spectroscopic techniques for the environmental monitoring of the recultivated uranium mine site

One uranium deposit exists in Hungary, with continuous radiological monitoring of the site. Nuclear spectroscopical methods are well established in order to study the problem concerning radionuclides. However, very limited information is available on the distribution and chemical form of uranium in the tailings sludge. In order to solve this complex analytical problem, a combination of different analytical methods is necessary. One of the most applied methods for studying the major elemental composition of particulate samples is electron probe microanalysis (EPMA). However, uranium and its daughter elements are often present only at trace amounts in the particles, below detection limit of EPMA. For most actinides that are long-lived radionuclides, microbeam X-ray fluorescence (μ-XRF) has superior sensitivity to determine elements in microparticles. Detection limits and applicability of EPMA and laboratory μ-XRF are discussed for localization of uranium-rich particles in the inhomogeneous tailings material. Laboratory μ-XRF provided an efficient way to identify these particles that can be easily relocated for further non-destructive microchemical investigations. Finally, for water analysis a simple and reliable method for U analysis is presented using total reflection X-ray fluorescence spectrometry (TXRF) that can be applied for on-site analysis in situations of accidental uranium contamination.

Characterization of the impurity profile at the SiO 2/Si interface using a combination of total reflection X-ray fluorescence spectrometry and successive etching of silicon

During the fabrication process of integrated circuits, dopant atoms segregate to energetically favorable sites at the interface between silicon and silicon dioxide. Because of the continuously shrinking device dimensions, this effect becomes even more significant. To describe it quantitatively within the framework of Technology Computer-Aided Design, the concentration profile at and near the SiO 2/Si interface has to be characterized accurately. Total Reflection X-ray Fluorescence Spectrometry (TXRF) with successive etching was used to determine the impurity profile at the SiO 2/Si interface with a resolution on the order of a nanometer.

Structural Organization of Essential Iron-Sulfur Clusters in the Evolutionarily Highly Conserved ATP-binding Cassette Protein ABCE1

The ABC protein ABCE1, formerly named RNase L inhibitor RLI1, is one of the most conserved proteins in evolution and is expressed in all organisms except eubacteria. Because of its fundamental role in translation initiation and/or ribosome biosynthesis, ABCE1 is essential for life. Its molecular mechanism has, however, not been elucidated. In addition to two ABC ATPase domains, ABCE1 contains a unique N-terminal region with eight conserved cysteines, predicted to coordinate iron-sulfur clusters. Here we present detailed information on the type and on the structural organization of the Fe-S clusters in ABCE1. Based on biophysical, biochemical, and yeast genetic analyses, ABCE1 harbors two essential diamagnetic [4Fe-4S](2+) clusters with different electronic environments, one ferredoxin-like (CPX(n)CX(2)CX(2)C; Cys at positions 4-7) and one unique ABCE1-type cluster (CXPX(2)CX(3)CX(n)CP; Cys at positions 1, 2, 3, and 8). Strikingly, only seven of the eight conserved cysteines coordinating the Fe-S clusters are essential for cell viability. Mutagenesis of the cysteine at position 6 yielded a functional ABCE1 with the ferredoxin-like Fe-S cluster in a paramagnetic [3Fe-4S](+) state. Notably, a lethal mutation of the cysteine at position 4 can be rescued by ligand swapping with an adjacent, extra cysteine conserved among all eukaryotes.

Determination of Water-soluble Atmospheric Aerosols Using Ion Chromatography

A field study was established to investigate the chemical composition of atmospheric aerosols in Chicago, IL. One goal of this study was to determine the influence of precursor trace gases and local meteorology on concentrations of secondary aerosol ionic species. This paper describes the method details, shows the method is analytically valid, and reports overall as well as some specific results found during the field study. Two particulate air samples were collected per day onto quartz fiber filters at the Loyola University Chicago Air Station during the summer months in 2002-2004. In parallel, mixing ratios of ozone and nitrogen oxides were monitored and weather parameters were recorded. Particulates were extracted from the filter substrates and the subsequent solutions were analyzed by ion chromatography for anions, including low molecular weight organic acids, and cations. A washing procedure was implemented to reduce the high background values of the quartz fiber filters. Method validation showed that the collection method was efficient for all ions with exception of nitrate, whose efficiency of 70% indicated losses caused by volatilization. The extraction method also proved efficient for both field and laboratory samples, and the repeatability of the method was high with relative standard deviations less than 10% for all ions. Reproducibility of the results was determined by comparison of sulfate to sulfur analyzed by total reflection X-ray fluorescence spectrometry and proved to be high as well. Concentrations differed significantly between the three summer studies due to varying levels of precursor species as a consequence of distinct temperatures and wind direction profiles.

Bulk determination of uranium and thorium in presence of each other by Total Reflection X-ray Fluorescence spectrometry

A study to assess the applicability of Total Reflection X-ray Fluorescence (TXRF) spectrometry as a microanalytical technique for the determination of uranium and thorium as major elements in presence of each other has been made. Effect of dilution of the sample on the analytical results has been investigated. It has been found that dilution of the sample does not affect the analytical results significantly. Also the analytical results of uranium and thorium are similar with different internal standards e.g. cobalt, gallium and yttrium. With a sample size of 10 μL and the concentrations of the analytes in the range of 1–50 μg/mL and total matrix concentration less than 200 μg/mL, the precision and accuracy of the method were found to be better than 3% (1 s) and 4%, respectively. For higher concentration ranges of the analyte (up to about 700 μg/mL), the precision and accuracy values were better than 6% (1 s) and 5%, respectively. The TXRF method has an advantage of using small sample volume of about 10 μL, produces very small radioactive waste and is nondestructive but requires dissolution of the sample.

Mechanism of Ni Removal from Si Materials Using Hydrogen Cyanide Aqueous Solutions

The mechanism of Ni removal from -covered Si specimens by HCN aqueous solutions has been investigated by means of total reflection X-ray fluorescence spectroscopy and X-ray photoelectron spectroscopy measurements. Ni contaminants on the surface are present in the form of SiO-NiOH. The removal mechanism consists of two steps, i.e., an initial fast process followed by a slow process. The rate-determining steps of both the processes are of the first order with respect to the concentration of cyanide ions . The fast and slow processes are tentatively attributed to the removal of SiO-NiOH on terraces and in sub-nanometer pores, respectively. The cleaning ability of the HCN aqueous solutions is much better than ammonia aqueous solutions, because of high reactivity to form nickel-cyanide complex ions and avoidance of readsorption of complex ions in the solutions.

Determination of heavy metals in macrozoobenthos from the rivers Tisza and Szamos by total reflection X-ray fluorescence spectrometry

In 2000, accidents in the Romanian mining industry in key catchment areas led to heavy metal contamination of the Hungarian rivers Tisza and Szamos resulting in substantial heavy metal loads in several sediments of the upper river basins. This enhanced metal content might have been bioaccumulated in benthic organisms during the following years. Therefore, the aim of this study was to test, whether the zoobenthic fauna showed an enhanced metal content 3 years after the industrial accident. Macrozoobenthic insect larvae (chironomids) were sampled 100 m below and above the confluent site of the rivers Tisza and Szamos during summer 2003 and for comparison purpose also in the river Maros, a tributary of the Tisza river, during 2005. In order to determine their heavy metal content, single specimens were prepared and analysed by Total Reflection X-ray Fluorescence Spectrometry (TRXF) according to the modified dry method. Fe was much lower and Mn and Zn much higher concentrated in benthos from the more contaminated Szamos river compared to the Tisza and Maros rivers. In this sense, the benthic organisms reflected very well the enhanced metal concentrations in the contaminated rivers being suitable as bioindicators of metal contamination. However, the sediment bioaccumulation factor was low at all sampling sites indicating a low bioavailability of trace metals for benthic organisms.

Characterization of pigments and colors used in ancient Egyptian boat models

The analyses of pigments originating from well dated ancient boat models found in Egyptian graves were used for characterization and for dating tasks of unknown objects. A nearly destruction free sampling technique using cotton buds was applied for sampling these valuable artifacts for a subsequent Total Reflection X-Ray Fluorescence Spectrometry (TXRF) analysis. Two relevant collections of Egyptian object of art were at our disposal, one of the Ägyptisches Museum Berlin and the second of the British Museum London. Three groups of colors were studied, they originate from white, red and blue/green paints, respectively. The results of the analyses performed on micro-amounts of paints (< 1 μg) show that some artifacts were misclassified and belong to other epochs. Some others were retouched with modern colors. In general, it can be stated that results obtained by Total Reflection X-Ray Fluorescence Spectrometry may dissipate some uncertainties when applying classical archaeological dating methods.

A new technique for the deposition of standard solutions in total reflection X-ray fluorescence spectrometry (TXRF) using pico-droplets generated by inkjet printers and its applicability for aerosol analysis with SR-TXRF

A new technique for the deposition of standard solutions on particulate aerosol samples using pico-droplets for elemental determinations with total reflection X-ray fluorescence spectrometry (TXRF) is described. It enables short analysis times without influencing the sample structure and avoids time consuming scanning of the sample with the exciting beam in SR-TXRF analysis. Droplets of picoliter volume (∼ 5–130 pL) were generated with commercially available and slightly modified inkjet printers operated with popular image processing software. The size of the dried droplets on surfaces of different polarity namely silicone coated and untreated quartz reflectors, was determined for five different printer types and ten different cartridge types. The results show that droplets generated by inkjet printers are between 50 and 200 μm in diameter (corresponding to volumes of 5 to 130 pL) depending on the cartridge type, which is smaller than the width of the synchrotron beam used in the experiments (< 1 mm at an energy of 17 keV at the beamline L at HASYLAB, Hamburg). The precision of the printing of a certain amount of a single element standard solution was found to be comparable to aliquoting with micropipettes in TXRF, where for 2.5 ng of cobalt relative standard deviations of 12% are found. However, it could be shown that the printing of simple patterns is possible, which is important when structured samples have to be analysed.

Assessment of the contamination problems resulting from the use of stainless steel needles in liver biopsies by total reflection X-ray fluorescence and inductively coupled plasma mass spectrometry

Percutaneous human liver biopsies taken from living patients could not be repeated; therefore considerable contamination was indirectly disproved. In the present study, the possible contamination of biopsy samples during sample collection was determined using a porcine liver model. Portions of porcine liver were cut by a quartz blade and treated the same as the steel needle biopsy samples. Concentrations determined in samples taken by a quartz device represented the non-contaminated values and were used to determine reproducibility of measurement and intra-individual variations. Additionally, multiple samples taken from a human liver of a patient suffering steatosis during autopsy were used to determine intra-individual variation of element concentrations. Concentration data of non-contaminated samples were compared to data of steel needle biopsy samples. To investigate the possible release of elements from the steel needles the samples were allowed to contact with the needle for different time in a refrigerator at 4 °C. Total reflection X-ray fluorescence spectrometry (TXRF) and inductively coupled plasma-mass spectrometry (ICP-MS) were applied for simultaneous determination of Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Mo and Pb because of the very low sample demand of the two selected techniques. Although the steel needles in the present study could not be substituted by polypropylene or Teflon utensils, it was demonstrated that the application of needle biopsy sampling in the reported analysis does not involve measurable contamination if contact time is kept to several minutes as usual in the clinical practice.

Recent and future developments in low power total reflection X-ray fluorescence spectroscopy

Today, energy-dispersive X-ray fluorescence (EDXRF) spectroscopy with low power X-ray tubes and thermoelectrically cooled detectors provide analytical performance which in the past was restricted to systems with kW power X-ray tubes and liquid nitrogen cooled Si(Li) detectors. Especially for low power TXRF spectrometers, the sensitivity could be improved by an order of one magnitude in the last 5 years. This progress was mainly based on improvements in quantum efficiency of all components and less on high power excitation sources. Recent developments caused further improvements in the analytical sensitivity as well as in the analytical performance. The introduction of a micro-focus X-ray tube increased the excitation power by a factor of 1.3. An additional improvement could be achieved by optimizing the detector window design. By optimizing the detector entrance geometry, the solid detection angle of a silicon drift detector (SDD) was increased by a factor of 1.8. In addition, the recent development of a new generation of silicon drift detectors increased the active detector area by a factor of three enhancing the peak to background ratio by a factor of two. Furthermore, the high-energy efficiency of this new detector type was significantly improved. As a result of all these improvements the detection limit for nickel could be decreased to a value of 1 pg.

Development of off-line layer chromatographic and total reflection X-ray fluorescence spectrometric methods for arsenic speciation

Rapid and low cost off-line thin layer chromatography–total reflection X-ray fluorescence spectrometry and overpressured thin layer chromatography–total reflection X-ray fluorescence spectrometry methods have been developed for separation of 25 ng of each As(III), As(V), monomethyl arsonic acid and dimethylarsinic acid applying a PEI cellulose stationary phase on plastic sheets and a mixture of acetone/acetic acid/water = 2:1:1 (v/v/v) as eluent system. The type of eluent systems, the amounts (25–1000 ng) of As species applied to PEI cellulose plates, injection volume, development distance, and flow rate (in case of overpressured thin layer chromatography) were taken into consideration for the development of the chromatographic separation. Moreover, a microdigestion method employing nitric acid for the As spots containing PEI cellulose scratched from the developed plates divided into segments was developed for the subsequent total reflection X-ray fluorescence spectrometry analysis. The method was applied for analysis of root extracts of cucumber plants grown in As(III) containing modified Hoagland nutrient solution. Both As(III) and As(V) were detected by applying the proposed thin layer chromatography/overpressured thin layer chromatography–total reflection X-ray fluorescence spectrometry methods.

How Trace Analytical Techniques Contribute to the Research and Development of Ge and III/V Semiconductor Devices

Ge and III/V semiconductor substrates are recently being investigated as a candidate material for the replacement of Si substrates in advanced micro-electronic devices. The reintroduction of this material requires engineering of the standard IC processing steps. In this paper, we present how the trace analytical techniques of total reflection X-ray fluorescence spectrometry (TXRF) and atomic absorption spectrometry (AAS) contribute to the realization of suitable processes to realize a high quality gate stack on Ge and GaAs substrates. A conventional application for these techniques lays in contamination control on incoming wafers. Besides this, we demonstrate some more advanced applications such as the determination of dopant concentrations (As in Ge), the study of passivation processes (S on Ge) and the characterization of nanometer thin layers (Si on Ge, HfO2 on Si).

Analysis of some chosen elements of cerebrospinal fluid and serum in amyotrophic lateral sclerosis patients by total reflection X-ray fluorescence

Trace elements play an important role in the human central nervous system. Significant variations of the concentration of trace elements in body fluids may occur in neurodegenerative diseases. In the present work an investigation of the elemental composition of the serum, and the cerebrospinal fluid in amyotrophic lateral sclerosis patients and a control group was performed. For the analysis of the body fluids Total reflection X-ray Fluorescence (TXRF) spectrometry was used. The samples were taken during routine diagnostic procedures. Na, Mg, Cl, K, Ca, Cu, Zn, and Br were determined in both fluids. In order to validate the results of analysis a serum standard reference material was measured. A t-test was applied to check if the mean concentrations of the elements are different for ALS and the control group. For the serum samples higher values for Br were found in the ALS group, for the cerebrospinal fluid lower values of Na, Mg and Zn as well as higher Ca values were found in the ALS group compared to the control group.

Cognitive impairment related changes in the elemental concentration in the brain of old rat

In order to evaluate the elemental concentration as a function of learning and memory deficiency, six different structures of the brain were analyzed by total reflection X-ray fluorescence spectrometry with synchrotron radiation (SR-TXRF). To evaluate the cognitive processes, the animals were tested in an adaptation of the Morris water maze. After the test, the animals were divided into two groups: cognitively healthy (control group) and cognitively impaired. The measurements were carried out at XRF beam line at Light Synchrotron Brazilian laboratory, Campinas, Brazil. The following elements were identified: Al, P, S, Cl, K, Ca, Ti, Cr, Fe, Cu, Zn, Br and Rb. K concentration was higher in all regions of the brain studied for control group than the cognitively impaired group. Moreover, the control group presented higher levels for P and Fe in the entorhinal cortex, in the temporal cortex (only P), in the hypothalamus and in the thalamus, than the cognitively impaired group. Br concentration in the animals which presented cognitive impairment was three times larger in the hypothalamus and thalamus, twice larger in temporal cortex and higher in visual cortex than the cognitively healthy group. Cu was more remarkable in the hippocampus and hypothalamus from the animals with cognitive impairment than the control group. We observed that the cognitively impaired group presented highest concentrations of Br and Cu in certain areas than the control group, on the other hand, this group presented highest levels of K for all brain areas studied.

Iodine determination in dietary supplement products by TXRF and ICP-AES spectrometry

About two-thirds of the Hungarian population is living in areas where drinking water contains less than 0.025 mg/L I 2. Iodine is an essential element required for the synthesis of thyroid hormones. The recommended daily allowance (RDA) is 0.150 mg for adults (WHO [17]). In the case of iodine deficiency mineral water containing iodine and seaweed products could serve as the natural source of this element. In the present study, the capability and limitations of total reflection X-ray fluorescence (TXRF) and inductively coupled plasma atomic emission (ICP-AES) spectrometry for the determination of iodine are discussed, in the case of commercially available dietary supplements and differently processed seaweed (kelp) products. Multi-mineral tablets and kelp samples were digested using concentrated nitric acid before analysis. Extraction using a 25% ammonia solution was proved to be effective as an alternative sample preparation procedure for seaweed and dietary supplement tablets containing iodine. Precipitation of silver iodide, as a sample preparation step of mineral water, was applied to prevent loss of volatile iodine during solvent evaporation. ICP-AES measurement was found to be seriously affected by spectral line coincidence between the prominent line of iodine and the adjacent phosphorus line. TXRF was proved to be line coincidence free and suitable for iodine analysis. TXRF determination of iodine in mineral water, in seaweed samples and in dietary supplement tablets has not been reported yet.

Application of Total Reflection X-ray Fluorescence Spectrometry to Small Glass Fragments

Total reflection X-ray fluorescence spectrometry (TXRF) has been applied for trace elemental analysis of small glass fragments. A small glass sample (a fragment with weight less than 0.5 mg) was decomposed by 100 microg of HF/HNO3 acid; the material was condensed to 10 microl and was dried on a Si wafer. Since the size of the dried residue on the Si wafer was less than 1 cm in diameter, an incident X-ray beam with about 1 cm in width could effectively excite elemental components in such a small glass fragment. The precision of the present technique was checked by analyzing the glass fragments (<0.5 mg) from NIST SRM612; the relative standard deviations (RSD) of less than 8.1% were achieved for elemental ratios that were normalized by Sr. Fragments (<0.5 mg) obtained from 23 figured sheet glasses were used as samples for estimating the utility of this technique to forensic discrimination. Comparison of five elemental ratios of Ti/Sr, Mn/Sr, Zn/Sr, Rb/Sr, and Pb/Sr calculated from X-ray fluorescence spectra was effective in distinguishing glass fragments that could not be differentiated by their refractive indexes (RI).

Analysis of low Z elements in various environmental samples with total reflection X-ray fluorescence (TXRF) spectrometry

Recently there is a growing interest in low Z elements such as carbon, oxygen up to sulphur and phosphorus in biological specimen. Total reflection X-ray fluorescence (TXRF) spectrometry is a suitable technique demanding only very small amounts of sample. On the other side, the detection of low Z elements is a critical point of this analytical technique. Besides other effects, self absorption may occur in the samples, because of the low energy of the fluorescence radiation. The calibration curves might be not linear any longer. To investigate this issue water samples and samples from human cerebrospinal fluid were used to examine absorption effects. The linearity of calibration curves in dependence of sample mass was investigated to verify the validity of the thin film approximation. The special requirements to the experimental setup for low Z energy dispersive fluorescence analysis were met by using the Atominstitute's TXRF vacuum chamber. This spectrometer is equipped with a Cr-anode X-ray tube, a multilayer monochromator and a SiLi detector with 30 mm 2 active area and with an ultrathin entrance window. Other object on this study are biofilms, living on all subaqueous surfaces, consisting of bacteria, algae and fungi embedded in their extracellular polymeric substances (EPS). Many trace elements from the water are bound in the biofilm. Thus, the biofilm is a useful indicator for polluting elements. For biomonitoring purposes not only the polluting elements but also the formation and growth rate of the biofilm are important. Biofilms were directly grown on TXRF reflectors. Their major elements and C-masses correlated to the cultivation time were investigated. These measured masses were related to the area seen by the detector, which was experimentally determined. Homogeneity of the biofilms was checked by measuring various sample positions on the reflectors.