Total Reflection X-ray Fluorescence Spectrometry Research Articles

Fast method for multielemental analysis of plants and discrimination according to the anatomical part by total reflection X-ray fluorescence spectrometry

Fast and reliable analytical methodologies are required for quality control of plants in order to assure human health. Ultrasound-assisted extraction in combination with total reflection X-ray fluorescence is proposed as a fast and simple method for multielemental analysis of plants on a routine basis. For this purpose, five certified reference materials have been analysed for the determination of P, K, Ca, Cr, Mn, Fe, Ni, Cu, Zn and Pb. Different extractant media (acids and oxidants) were tried. A mixture of diluted HNO3+HCl+HF, was selected as the best option for the achievement of complete extractions. Accurate and precise results can be reached in most cases along with a high sample throughput. Different plants (i.e., herbs, spices and medicinal plants) were analysed. Linear discriminant analysis together with the elemental concentrations allowed the differentiation of commercial preparations corresponding to flower, fruit and leaf.

Status of trace and toxic elements pollution in creek ecosystem using TXRF method

The economic development worldwide has brought in its wake many changes in the environment. Marine ecosystem which forms a part of this environment has been subjected to impact of industrialisation and urbanization. The study has been carried out in the creek ecosystem of Mumbai receiving the effluents from industrial and urban settlements. The trace elements such as P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb, As, Rb and Sr were analysed in the creek water collected from the side receiving industrial effluent and discharges from the urban settlements using total reflection X-ray fluorescence spectrometry. On comparing the concentration of the trace element from the mid stream water of the creek with the water samples collected from the industrial and city effluent receiving side, it was found that the concentration of P, Ca, Mn, Fe, Co, Cu, Zn, Pb and As were found higher in the industrial side of the creek whereas V, Cr and Ni concentration were found higher in the samples collected from the side receiving city effluent.

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.

Chemical interactions in the layered system BC x N y /Ni(Cu)/Si, produced by CVD at high temperature

Layered samples Si(100)/C/Ni/BC(x)N(y) and Si(100)/C/Cu/BC(x)N(y) were produced by physical vapor deposition of a metal (Ni, Cu, resp.) and low-pressure chemical vapor deposition of the boron carbonitride on a Si(100) substrate. Between the Si and the Ni (Cu) and on the surface of the Ni (Cu) layer, thin carbon layers were deposited, as a diffusion barrier or as a protection against oxidation, respectively. Afterwards, the surface carbon layer was removed. As precursor, trimethylamine borane and, as an auxiliary gas, H(2) and NH(3) were used, respectively. The chemical compositions of the layers and of the interfaces in between were characterized by total-reflection X-ray fluorescence spectrometry combined with near-edge X-ray absorption fine-structure spectroscopy, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry. The application of H(2) yielded the BC(x)N(y) compound whereas the use of NH(3) led to a mixture of h-BN and graphitic carbon. At the BC(x)N(y)/metal interface, metal borides could be identified. At the relatively high synthesis temperature of 700 °C, broad regions of Cu or Ni and Si were observed between the metal layer and the substrate Si.

Steps toward accurate large-area analyses of Genesis solar wind samples: evaluation of surface cleaning methods using total reflection X-ray fluorescence spectrometry

Total reflection X-ray fluorescence spectrometry (TXRF) was used to analyze residual surface contamination on Genesis solar wind samples and to evaluate different cleaning methods. To gauge the suitability of a cleaning method, two samples were analyzed following cleaning by lab-based TXRF. The analysis comprised an overview and a crude manual mapping of the samples by orienting them with respect to the incident X-ray beam in such a way that different regions were covered. The results show that cleaning with concentrated hydrochloric acid and a combination of hydrochloric acid and hydrofluoric acid decreased persistent inorganic contaminants substantially on one sample. The application of CO2 snow for surface cleaning tested on the other sample appears to be effective in removing one persistent Genesis contaminant, namely germanium. Unfortunately, the TXRF analysis results of the second sample were impacted by relatively high background contamination. This was mostly due to the relatively small sample size and that the solar wind collector was already mounted with silver glue for resonance ion mass spectrometry (RIMS) on an aluminium stub. Further studies are planned to eliminate this problem. In an effort to identify the location of very persistent contaminants, selected samples were also subjected to environmental scanning electron microscopy. The results showed excellent agreement with TXRF analysis.

Dispersive liquid–liquid microextraction using diethyldithiocarbamate as a chelating agent and the dried-spot technique for the determination of Fe, Co, Ni, Cu, Zn, Se and Pb by energy-dispersive X-ray fluorescence spectrometry

Dispersive liquid–liquid microextraction (DLLME) using sodium diethyldithiocarbamate (DDTC) as a chelating agent was investigated for the simultaneous determination of iron, cobalt, nickel, copper, zinc, selenium and lead ions in water samples. The procedure was performed using 5mL of the sample, 100μL of a 0.5% solution of DDTC, 30μL of carbon tetrachloride (extraction phase) and 500μL of methanol (disperser solvent). The experiments showed that Fe, Co, Ni, Cu, Zn and Pb can be simultaneously extracted at a pH of 5 and that Se can be extracted at a pH of 2–3. The results were compared with those obtained using ammonium pyrrolidine dithiocarbamate as a chelating agent. For all analytes, a linear range was observed up to 0.4μgmL−1. If Fe and Zn are present in concentrations 10 times higher than those of the other analytes, then the linearity is observed up to 0.2μgmL−1. In the present study, the organic phase that contained preconcentrated elements was deposited onto a Millipore filter and measured using energy-dispersive X-ray fluorescence spectrometry. The obtained detection limits were 2.9, 1.5, 2.0, 2.3, 2.5, 2.0 and 3.9ngmL−1 for Fe, Co, Ni, Cu, Zn, Se and Pb, respectively. This combination of DLLME and the dried-spot technique is promising for multielement analyses using other spectroscopy techniques, such as laser ablation‐inductively coupled plasma‐mass spectrometry, laser-induced breakdown spectroscopy or total-reflection X-ray fluorescence spectrometry.

A total reflection X‐ray fluorescence method for the determination of chlorine at trace levels in nuclear materials without sample dissolution

A total reflection X‐ray fluorescence (TXRF) method for the determination of chlorine at trace levels in nuclear fuel samples is described. Chlorine present in trace concentrations in nuclear fuel materials such as U3O8, (U,Pu)C, PuO2 and Pu‐alloys was first separated from the solid matrix by pyrohydrolysis as HCl and was collected in 5 mM NaOH solution. This solution was analyzed for chlorine by TXRF spectrometry using Cl Kα analytical line excited by W Lα. Cobalt was used as internal standard. The precision for such chlorine determination was found to be within 27% (n = 4) when the analysis was carried out in air atmosphere. This could be improved to 8% by making TXRF measurement in flowing helium atmosphere. The results obtained from TXRF determinations were also compared with those obtained from ion chromatography (IC) and were in good agreement. The collection of distillate during pyrohydrolysis in NaOH helped in counterchecking loss of chlorine during TXRF sample preparation. The average deviation of TXRF‐determined values in helium‐purged TXRF measurements with IC determined values (as chloride) was 15% at a chlorine concentration level in the range of 1–70 µg/mL. Copyright © 2012 John Wiley & Sons, Ltd.

Microanalytical investigation of nematodes

The chemical characterization of individual free-living nematodes is a challenge due to their small size and correspondingly, their low dry mass (1–3μg). The concentrations of minor (S, P, Ca, K) and trace elements (Fe, Zn, Cu, Ni, and Mn) of individual specimens (Xiphinema Vuittenezi) were determined by total reflection X-ray fluorescence (TXRF) spectrometry following a two step sample preparation procedure. The mean concentrations of minor and trace elements changed in the range of 1–4 and 0.01–0.4ng/μg, respectively. The relative standard deviation varied between 9.4 and 25.3% which was influenced not only by the analytical procedure but also by the biological deviations among the eleven investigated specimens. The stress effect caused by CuSO4 treatment resulted in significant change in the nematodes only in their Zn content. In the lack of certified reference material, the TXRF method was checked by inductively coupled plasma mass spectrometry (ICP-MS) analyzing solutions of 100 digested nematodes. The carbon and nitrogen content of nematodes was also measured by total C/N analyzer and their ratio amounted to 4.78±0.31 which is lower than the values published for the bacterial or fungal feeding ones. The way of copper uptake was investigated by scanning electron microscopy (SEM). Nematode treated with copper-nitrate was pecked out at the mid-body using focused ion beam (FIB) technique. In order to preserve the cross-section to be investigated, platinum coating was applied prior to the FIB operation. Energy dispersive X-ray analysis was performed along the cross-section measuring the distribution of platinum, sulfur and copper. It has been found that the sulfur and copper distributions were fairly similar following the copper treatment, and these elements had the highest concentration in the cuticle.

Methodology for Measuring Trace Metal Surface Contamination on Pv Silicon Substrates

The production of high efficiency PV cells requires a strict control on metal contamination levels. Metals like Cu and Fe are well known to cause lifetime degradation in silicon. Analytical methodologies for determination of surface metal contamination have been well established for mirror polished, also referred to as chemical mechanical polished (CMP) silicon substrates [1]. It will be explained why these methods cannot be merely applied to photovoltaic (PV) wafers because of the large roughness and specific topography of the surface. Here we extend and adapt these analytical methodologies for surface metal contamination analysis on PV substrates also referred to as PV wafers. We demonstrate how vapour phase decomposition droplet collection (VPD-DC) in combination with total reflection X-ray fluorescence spectroscopy (TXRF) or inductively coupled plasma mass spectrometry (ICP-MS) has been modified to accommodate analysis on a non-polished PV silicon wafer surface. In addition we demonstrate how metal contamination on as-cut PV wafers has been determined by liquid surface etching (LSE), i.e. an oxidizing and slow etching solution used to dissolve metal contaminants, followed by TXRF analysis. Measurements of as-cut wafers shows the presence of Fe, Cu and Zn in very high concentrations (up to more than 1x1013at/cm2), residuals of the brass-coated steel wires used during wire sawing [10].

Use of high-intensity sonication for pre-treatment of biological tissues prior to multielemental analysis by total reflection X-ray fluorescence spectrometry

In this work, two ultrasound-based procedures are developed for sample preparation prior to determination of P, K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, As, Se and Sr in biological tissues by total reflection X-ray fluorescence spectrometry. Ultrasound-assisted extraction by means of a cup-horn sonoreactor and ultrasonic-probe slurry sampling were compared with a well-established procedure such as magnetic agitation slurry sampling. For that purpose, seven certified reference materials and different real samples of animal tissue were used. Similar accuracy and precision is obtained with the three sample preparation approaches tried. Limits of detection were dependent on both the sample matrix and the sample pre-treatment used, best values being achieved with ultrasound-assisted extraction. Advantages of ultrasound-assisted extraction include reduced sample handling, decreased contamination risks (neither addition of surfactants nor use of foreign objects inside the extraction vial), simpler background (no solid particles onto the sample carrier) and improved recovery for some elements such as P. A mixture of 10% v/v HNO3+20–40% v/v HCl was suitable for extraction from biological tissues.

Solid Phase Extraction of Ultra Trace Copper Using Octadecyl Silica Bonded Phase Membrane Disks Modified by a New Symmetric Schiff Base Ionophore Prior to FAAS Determination

A very selective, reliable and precise method for rapid separation of the trace amounts of copper in aqueous samples using octadecyl silica bonded phase membrane disks modified by N,N-ethylene-bis-(3-formyl-5-methyl salicyl aldymine) combined with flame atomic absorption spectrometric determination has been established. All the affecting experimental variables such as pH, amount of modifier, eluent type, sample and eluent flow-rate, foreign ions and disk capacity were also investigated. The target analyte (trace copper) was quantitatively retained at pH=4, and eluted with 8 mL of HCl (1M) and HNO3 0.5 M each containing 2.0% (v/v) methanol applying flow rates of 50 mL min-1 and 15 mL min-1 for sample introduction and elution steps, respectively. The proposed method exhibits a wide linear dynamic range over 5- 150 ng mL-1 and reproducibility at the most 3%. It also permits an enrichment factor of about 400 or higher and a detection limit of 0.005 ng mL-1. The method has been successfully applied for isolation and determination of copper in different aqueous, real samples, peppers and standard alloys. Keywords: Copper(II), Flame atomic absorption spectrometry, Modifier, N,N'-ethylene bis-(3-formyl-5-methyl salicyl aldymine) (EFMA), Solid phase extraction, Schiff Base Ionophore, Total reflection X-ray fluorescence (TXRF) spectrometry, Inductively coupled plasma optical emission spectrometry (ICP-OES), Atomic fluorescence spectrometry (AFS), Environmental samples

Impacts of bitumen deposit on surface waters

Purpose – This paper aims to examine the quality of the surface waters of the bitumen deposit area of Nigeria and also to establish the relationship between the deposit and the waters. Design/methodology/approach – Physico-chemical parameters were measured using standard analytical procedures, while the elemental contents were determined using total reflection X-ray fluorescence spectroscopy. Data acquired were interpreted using statistical techniques – charts, t-test, pollution index (PI) and cross-plot analysis. Findings – A river located close to the bitumen well contained the highest concentrations of metals that are known to be associated with hydrocarbon formation. Comparison of the levels of the analyzed parameters in the waters with their standard permissible limits showed that the levels of Cl−, SO42-, total alkalinity and Cr, Mn, Fe, Ni, Cu, Zn and Pb in the river very close to the capped bitumen well and big rivers were high and low in the small streams. This was corroborated by their pollution index values. Results of the cross-plot analysis of the waters-river close to bitumen well/bitumen (R2=0.5); small streams/bitumen (R2=0.8) and big rivers/bitumen (R2=0.2) showed moderate; strong and weak positive correlations respectively, suggesting moderate, strong and weak inter-element correlations respectively between the sets of waters and the Nigerian bitumen deposit, and also establishing relationships between the deposit and the surface waters. Originality/value – The paper provides insight into the potability of the waters; establishment of the inter-element relationship between the bitumen deposit and the waters. These results can serve as a fingerprint for bitumen exploration elsewhere and for similar mineral deposit settings.

Microanalytical method development for Fe, Cu and Zn determination in colorectal cancer cells

Microanalytical methods suitable for the determination of Fe, Cu in HT-29 (human colon adenocarcinoma) cells treated with different iron compounds (Fe(II) sulfate, Fe(III) chloride, Fe(III) citrate and Fe(III) transferrin) and cultured in medium supplemented or not with 10% (v/v) fetal calf serum (FCS) by total reflection X-ray fluorescence spectrometry (TXRF) and simultaneous graphite furnace atomic absorption spectrometry (GF-AAS) were developed. The developed TXRF method was also suitable for Zn determination in the samples. The main advantage of the proposed methods is the execution of all sample preparation steps following incubation and prior to the elemental analysis in the same Eppendorf tubes. Sample preparation was performed at microscale (115μL sample volume) with 65% nitric acid and 30% hydrogen peroxide. According to scanning electron microscopic measurements, the organic matrix of the cell samples could be eliminated to the extent that accurate results were obtained for Cu and Fe by analyzing the same samples by TXRF and GF-AAS. Concerning the iron uptake, HT-29 cells incubated in FCS-free medium contained Fe in cca. 5–50 times higher amounts compared to cells cultured in FCS supplemented medium. Pronounced differences in the iron uptake compared to the iron supply (inorganic vs. organic chelated as well as iron(II) vs. iron(III)) were observed in the case of cell lines incubated in FCS-free medium.

Possibilities and limitations of the total reflection X-ray fluorescence spectrometry for the determination of low Z elements in biological samples

The analytical capability of the laboratory scale vacuum total reflection X-ray fluorescence (TXRF) spectrometer (Wobistrax) was studied for the determination of the Z elements (Na, Mg, P, S, K and Ca) in different biological matrices represented by the following certified reference materials: MURST-ISS-A2 Antarctic krill, IAEA-331 spinach, NIST 1577a bovine liver, and SERONORM™ Trace Elements Serum Level 1.First, the stability of the response factors (relative sensitivity) against Ti internal standard was checked in the concentration range of 1 to 1000mg/L in a diluted nitric acid matrix. It has been found that the upper limit of the analytical concentration range for K and Ca can be as high as 1000mg/L; on the other hand, the remaining elements cannot be determined above a concentration of some tens mg/L.The established response factors were used for the elemental analysis of the four certified reference materials after normal-volume microwave assisted acid digestion. In the case of the serum sample, different preparation methods were compared as follow: direct analysis, microwave assisted acid digestion in normal-volume and micro-vessels, as well as the vapor-phase digestion directly on the TXRF carrier plates.On the basis of the results, the normal-volume digestion results in rather high dilution of the samples; thus, elements at low concentration could not be detected in some of the samples. On the other hand, this method offers the highest rate of both organic matrix decomposition and inorganic matrix dilution; thus, the background and the standard deviation of the results were the lowest. In general, this method was found to be useful for the analysis of samples with high dissolved (organic+inorganic) content if the analytes are present at a concentration considerable above the quantification limit.In the case of the microscale and the vapor-phase digestion, both the organic and inorganic matters remain at elevated concentration; thus, higher background and self-absorption of the fluorescent radiation occurred, deteriorating the analytical performance.

Accumulation and distribution of iron, cadmium, lead and nickel in cucumber plants grown in hydroponics containing two different chelated iron supplies

Cucumber plants grown in hydroponics containing 10 μM Cd(II), Ni(II) and Pb(II), and iron supplied as Fe(III) EDTA or Fe(III) citrate in identical concentrations, were investigated by total-reflection X-ray fluorescence spectrometry with special emphasis on the determination of iron accumulation and distribution within the different plant compartments (root, stem, cotyledon and leaves). The extent of Cd, Ni and Pb accumulation and distribution were also determined. Generally, iron and heavy-metal contaminant accumulation was higher when Fe(III) citrate was used. The accumulation of nickel and lead was higher by about 20% and 100%, respectively, if the iron supply was Fe(III) citrate. The accumulation of Cd was similar. In the case of Fe(III) citrate, the total amounts of Fe taken up were similar in the control and heavy-metal-treated plants (27–31 μmol/plant). Further, the amounts of iron transported from the root towards the shoot of the control, lead- and nickel-contaminated plants were independent of the iron(III) form. Although Fe mobility could be characterized as being low, its distribution within the shoot was not significantly affected by the heavy metals investigated.

Application of total reflection X-ray fluorescence spectrometry for trace elemental analysis of rainwater

Applicability of total reflection X-ray fluorescence (TXRF) spectrometry for trace elemental analysis of rainwater samples was studied. The study was used to develop these samples as rainwater standards by the National University of Singapore (NUS). Our laboratory was one of the participants to use TXRF for this study. The rainwater sample obtained from NUS was analysed by TXRF and the trace elements Mn, Fe, Ni, Cu, Zn, V and Pb were determined as required by the NUS. The average precision was found to be within 16% and the TXRF-determined elemental concentrations of these elements were below 20 μg/l. The average deviation of TXRF-determined values from the certified values were 20% (excluding the deviation for Fe and V which were comparatively high). Apart from the above elements, S, K, Ca, Rb, Sr, Ba and Br were also determined by TXRF and were found to be in the range of 0.2 to 191 μg/l. TXRF-determined values of our laboratory played an important role in the certification of concentration of seven elements in this rainwater sample which was later developed as a rainwater standard.

Method and mechanism of vapor phase treatment–total reflection X-ray fluorescence for trace element analysis on silicon wafer surface

Vapor phase treatment (VPT) is a pretreatment with hydrofluoric acid vapor to raise the sensitivity of total reflection X-ray fluorescence spectroscopy (TXRF) for trace metal analysis on silicon wafers. The International Organization for Standardization/Technical Committee 201/Working Group 2 (ISO/TC201/WG2) has been investigating the method to analyze 10 9 atoms/cm 2 level of metallic contamination on the silicon wafer surface. Though VPT can enhance the TXRF signal intensity from the metallic contamination, it has turned out that the magnitude of the enhancement varies with the type of methods and the process conditions. In this study, approaches to increase TXRF intensity by VPT are investigated using a fuming chamber in an automated VPD instrument. Higher signal intensity can be obtained when condensation is formed on the sample surface in a humidifying atmosphere and with a decreasing stage temperature. Surface observations with SEM and AFM show that particles with ~ 4 μm in diameter are formed and unexpectedly they are dented from the top surface level.

Picoliter solution deposition for total reflection X-ray fluorescence analysis of semiconductor samples

A deposition system capable of delivering picoliter quantities of solution in programmable arrays was investigated as a method for sample preparation for total reflection X-ray fluorescence (TXRF) spectroscopy. Arrays of trace metals in solution were deposited on Si wafers. The array deposits provide a capability of depositing closely spaced (100 μm or less), typically 5–20 μm diameter droplets in an area that can be matched to the analysis spot of the TXRF detector. The dried depositions were physically characterized and the effect of deposition type and matrix on the TXRF signal was investigated.

Analytical determination of selenium in medical samples, staple food and dietary supplements by means of total reflection X-ray fluorescence spectroscopy

Selenium is essential for many aspects of human health and, thus, the object of intensive medical research. This demands the use of analytical techniques capable of analysing selenium at low concentrations with high accuracy in widespread matrices and sometimes smallest sample amounts. In connection with the increasing importance of selenium, there is a need for rapid and simple on-site (or near-to-site) selenium analysis in food basics like wheat at processing and production sites, as well as for the analysis of this element in dietary supplements. Common analytical techniques like electrothermal atomic absorption spectroscopy (ETAAS) and inductively-coupled plasma mass spectrometry (ICP-MS) are capable of analysing selenium in medical samples with detection limits in the range from 0.02 to 0.7 μg/l. Since in many cases less complicated and expensive analytical techniques are required, TXRF has been tested regarding its suitability for selenium analysis in different medical, food basics and dietary supplement samples applying most simple sample preparation techniques. The reported results indicate that the accurate analysis of selenium in all sample types is possible. The detection limits of TXRF are in the range from 7 to 12 μg/l for medical samples and 0.1 to 0.2 mg/kg for food basics and dietary supplements. Although this sensitivity is low compared to established techniques, it is sufficient for the physiological concentrations of selenium in the investigated samples.

Inorganic pigment study of the San Pedro Gonzalez Telmo Sibyls using total reflection X-ray fluorescence

This article describes the study carried out on a series of oil paintings on canvas from the eighteenth century that were restored at Centro de Producción e Investigación en Restauración y Conservación Artística y Bibliográfica - Tarea (CEIRCAB-Tarea), Buenos Aires, Argentina: the San Pedro González Telmo Sibyls. Experimental study was undertaken to identify inorganic pigments and the technique used in their confection; and, in this way, try to add information about their local origin. Therefore special emphasis was put to infer technologies used in the manufacturing of these paintings. Elemental analysis was performed by total reflection X-ray fluorescence spectrometry (TXRF) and complemented by optical and polarized light microscopy. Microsampling was carefully done over areas of the paintings which were damaged and where a small additional loss will not be noticed. This investigation has shown that a variety of pigments were used, namely earth pigments (red and yellow ochres), white lead, vermilion, etc., and they were used either pure or in mixtures. This characterization helped conservators in their decisions regarding a better understanding of the deterioration processes. In addition, this research about the material composition allowed the art historians and restorers the possibility to obtain information about where, when or by whom The San Pedro González Telmo Sibyls may have been painted.