Applicability Of Total Reflection X-ray Fluorescence Research Articles

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.

Monitoring dissolved active trace elements in biogas plants using total reflection X‐ray fluorescence spectrometry

Generally, full‐scale biogas plants require trace elements supplementation to sustain a stable process. The aim was to apply total reflection X‐ray fluorescence (TXRF) to monitor the dissolved, active elements, for the first time, at μg/L levels in biogas plants. The digester liquid is comparable to sludge with high solids content and high salt concentrations. The ions are usually measured in the dried fermenter slurry after acid digestion in its inactive bound form, although microorganisms can take up only dissolved ions as active agent. In this study, a procedure was developed to monitor dissolved ions in such environmental processes to prevent an overdose or underdose. The analytical figures of merit considered were the lowest possible limit of detection, the recovery of spiked ions and linearity. Samples were spiked with nickel, selenium and tungsten in the range of 10–200 μg/L. Highest recovery rates of >93% for concentrations of 10 to <100 μg/L were obtained after the samples were centrifugated twice, followed by application of microwave‐assisted acid digestion. The calculated lowest limit of detection was 2–4 μg/L. The developed method was first tested in laboratory‐scale biogas digesters with wheat straw as substrate. Successful application of TXRF was also achieved in a full‐scale biogas plant to estimate the dynamics of “active” trace element ions in the range of 2–1,000 μg/L for several months. Therefore, cost‐effective biogas plant management is possible through the application of TXRF spectrometry to monitor trace elements.

Total Reflection X-Ray Fluorescence Spectroscopy

Total reflection X-ray fluorescence (TXRF) is widely used in trace elements, ultra-trace element, and multi-element analysis due to its low detection limit and low energy spectrum background count. This article studies the development and application of TXRF. The development of TXRF can be divided into three stages. The first stage: Total reflection was first presented in 1971 to the publication of the first monograph about TXRF in 1997, mainly the theoretical research of TXRF and the application in single element analysis; the second stage: 1998 to 2017, during this stage, TXRF has developed rapidly, from single element analysis to multi-element simultaneous analysis, mainly used in geology, environment, chemistry, medicine, etc. field; the third stage: based on the extensive application of TXRF, conduct in-depth research on its basic theory, further improve the performance of the instrument, and achieve more accurate analysis results.

Direct Determination of Oxidation States of Uranium in Mixed-Valent Uranium Oxides Using Total Reflection X-ray Fluorescence X-ray Absorption Near-Edge Spectroscopy.

Total reflection X-ray fluorescence (TXRF)-based X-ray absorption near-edge spectroscopy has been used to determine the oxidation state of uranium in mixed-valent U3O8 and U3O7 uranium oxides. The TXRF spectra of the compounds were measured using variable X-ray energies in the vicinity of the U L3 edge in the TXRF excitation mode at the microfocus beamline of the Indus-2 synchrotron facility. The TXRF-based X-ray absorption near-edge spectroscopy (TXRF-XANES) spectra were deduced from the emission spectra measured using the energies below and above the U L3 edge in the XANES region. The data processing using TXRF-XANES spectra of U(IV), U(V), and U(VI) standard compounds revealed that U present in U3O8 is a mixture of U(V) and U(VI), whereas U in U3O7 is mixture of U(IV) and U(VI). The results obtained in this study are similar to that reported in literature using the U M edge. The present study has demonstrated the possibility of application of TXRF for the oxidation state determination and elemental speciation of radioactive substances in a nondestructive manner with very small amount of sample requirement.

Determination of element levels in human serum: Total reflection X-ray fluorescence applications

Deficiency or excess of elements could disrupt proper functioning of the human body and could lead to several disorders. Determination of their concentrations in different biological human fluids and tissues should become a routine practice in medical treatment. Therefore the knowledge about appropriate element concentrations in human organism is required. The purpose of this study was to determine the concentration of several elements (P, S, Cl, K, Ca, Cr, Fe, Cu, Zn, Se, Br, Rb, Pb) in human serum and to define the reference values of element concentration. Samples of serum were obtained from 105 normal presumably healthy volunteers (66 women aged between 15 and 78years old; 39 men aged between 15 and 77years old). Analysis has been done for the whole studied population and for subgroups by sex and age. It is probably first so a wide study of elemental composition of serum performed in the case of Świętokrzyskie region. Total reflection X-ray fluorescence (TXRF) method was used to perform the elemental analysis. Spectrometer S2 Picofox (Bruker AXS Microanalysis GmbH) was used to identify and measure elemental composition of serum samples. Finally, 1st and 3rd quartiles were accepted as minimum and maximum values of concentration reference range.

Application of TXRF for burn leach test of TRISO coated UO2 particles

A Total Reflection X-Ray Fluorescence (TXRF) methodology, employing burn-leach test, was developed to assess the quality of SiC layer in tristructural isotropic (TRISO) coated UO2 particles prepared in BARC. The coated particles were heated at 1,123 K for about 96 h to constant weight. The calcined particles, thus obtained, were then heated in suprapure concentrated nitric acid. The supernatant was analysed for trace elements by TXRF. No uranium was detected in this supernatant solution. The study demonstrates the good quality of SiC layer and applicability of TXRF for burn leach test of TRISO coated UO2 particles prepared.

Evaluation of bioaccumulation kinetics of gold nanorods in vital mammalian organs by means of total reflection X-ray fluorescence spectrometry.

This work presents the first application of total-reflection X-ray fluorescence (TXRF) spectrometry, a new and powerful alternative analytical method, to evaluation of the bioaccumulation kinetics of gold nanorods (GNRs) in various tissues upon intravenous administration in mice. The analytical parameters for developed methodology by TXRF were evaluated by means of the parallel analysis of bovine liver certified reference material samples (BCR-185R) doped with 10 μg/g gold. The average values (n = 5) achieved for gold measurements in lyophilized tissue weight were as follows: recovery 99.7%, expanded uncertainty (k = 2) 7%, repeatability 1.7%, detection limit 112 ng/g, and quantification limit 370 ng/g. The GNR bioaccumulation kinetics was analyzed in several vital mammalian organs such as liver, spleen, brain, and lung at different times. Additionally, urine samples were analyzed to study the kinetics of elimination of the GNRs by this excretion route. The main achievement was clearly differentiating two kinds of behaviors. GNRs were quickly bioaccumulated by highly vascular filtration organs such as liver and spleen, while GNRs do not show a bioaccumulation rates in brain and lung for the period of time investigated. In parallel, urine also shows a lack of GNR accumulation. TXRF has proven to be a powerful, versatile, and precise analytical technique for the evaluation of GNRs content in biological systems and, in a more general way, for any kind of metallic nanoparticles.

Nanoliter deposition unit for pipetting droplets of small volumes for Total Reflection X-ray Fluorescence applications

A nanoliter droplet deposition unit was developed and characterized for application of sample preparation in TXRF. The droplets produced on quartz reflectors as well as on wafers show a good reproducibility, also the accuracy of the pipetted volume could be proved by a quantitative TXRF analysis using an external standard. The samples were found to be independent of rotation of the sample carrier. Angle scans showed droplet residue behavior, and the fluorescence signal is relatively invariant of the angle of incidence below the critical angle, which is useful for producing standards for external calibration for semiconductor surface contamination measurements by TXRF. Further it could be demonstrated that the nanoliter deposition unit is perfectly able to produce patterns of samples for applications like the quantification of aerosols collected by impactors.

Study on trace elements behaviour in cancerous and healthy tissues of colon, breast and stomach: Total reflection X-ray fluorescence applications

In this work Total-reflection X-ray fluorescence (TXRF) was used to analyse healthy and cancerous tissues of the same individual along several contiguous thin sections of each tissue. Thirty two samples (16 pairs) of breast tissue, 30 samples (15 pairs) of intestine tissue and 10 samples (5 pairs) of stomach tissue were analysed. The samples were obtained in Civil Hospitals of Germany (Dortmund) and Portugal (Lisbon). The elemental distribution of P, S, Cl, K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Se, Br, Rb, Sr and Pb in these samples was studied. Descriptive statistics based on bar graphics and hypotheses tests and also an automatic classification based on hierarchical grouping analysis was used for the several analysed tissues. It was shown that the behaviour of the elements is tissue dependent. Some elements, like P and K exhibit the same behaviour in all the analysed tissue types. They have increased concentrations in all cancerous tissues. Unlike, other elements like Br show completely different behaviour depending on the tissue: similar concentration in healthy and cancerous stomach, decreased levels in colon cancerous tissues and enhanced concentrations in breast was observed. Moreover cancer tissues present decreased Se concentrations on colon and increased on breast.

Application of total-reflection X-ray fluorescence for the determination of lead, calcium and zinc in size-fractionated marine aerosols

As has been demonstrated by several groups in the last years, aerosols can be sampled in size-segregated form with multistage cascade impactors and analyzed directly by total-reflection X-ray fluorescence (TXRF) for their trace element content. The advantage of this method is to simplify the analysis by omitting the digestion step. Furthermore, it allows short sampling times because of the high sensitivity of TXRF. We present data for three typical trace elements (Pb, Ca and Zn) having distinct size distribution properties. The overall precision of the method was derived from 22 parallel samplings with two impactors of the same type, carried out at three different sampling sites in the marine environment. The bias between parallel samples of the same impactor stage for particle sizes between 0.25 and 8 μm was found to be 43%, as a mean value for Pb, Ca and Zn. This estimate for the precision is the basis for interpreting differences in mean size distributions measured at different sites. Results for 144 impactor samples taken during field campaigns in the North Eastern Atlantic, the North Sea and the Baltic Sea are presented as mean normalized size distributions. The size distribution for Pb in the most remote location showed a significant reduction of mass in an intermediate size class. Ca size distributions showed slightly more scatter, which is attributed to the larger dynamics of the coarse particle fraction. Zn shows the highest variability. Even more Zn has been found in the coarse particle fraction (2–10 μm) under on-shore blowing wind conditions, which leads to the hypothesis of a marine source associated with sea spray production. © 1997 Elsevier Science B.V.

Elemental Analysis of Environmental Samples by Total Reflection XRay Fluorescence: a Review

A review of total reflection x-ray fluorescence (TXRF) as an effective excitation mode for energy-dispersive x-ray spectral analysis is presented. The instrumental conditions of excitation under grazing incidence (ψ<0.1°) are emphasized and the analytical features of powerful detection and simple and reliable quantification are characterized. The applicability of TXRF to environmental analyses is illustrated by some typical examples. The analysis of pure water samples leads to detection limits at the ppt (ng/l) level. A special matrix separation is only needed for river, sea and waste waters. The analysis of air dust is directly possible with a sampling volume of 1 m3 and a sampling time of 1 h. Organ tissue can be analysed down to the lower ppm range after freeze-cutting of μm thick sections. Plant material has to be pulverized and digested prior to analysis, e.g. with nitric acid. In combination with a chromatographic separation, speciation is made possible for small 0.5 ml fractions, e.g. for vegetable foodstuffs. For all these applications a multi-element determination can be carried out, for about 20–25 elements simultaneously. Simple and reliable quantification is effected by internal standardization. The reliability of the method has been proved by intercomparison tests. Second-generation instruments that are compact and user-friendly are now commercially available.

Elemental Analysis of Environmental Samples by Total Reflection X-Ray Fluorescence: a Review

A review of total reflection x-ray fluorescence (TXRF) as an effective excitation mode for energy-dispersive x-ray spectral analysis is presented. The instrumental conditions of excitation under grazing incidence (ψ < 0.1°) are emphasized and the analytical features of powerful detection and simple and reliable quantification are characterized. The applicability of TXRF to environmental analyses is illustrated by some typical examples. The analysis of pure water samples leads to detection limits at the ppt (ng/l) level. A special matrix separation is only needed for river, sea and waste waters. The analysis of air dust is directly possible with a sampling volume of 1 m 3 and a sampling time of 1 h. Organ tissue can be analysed down to the lower ppm range after freeze-cutting of μm thick sections. Plant material has to be pulverized and digested prior to analysis, e.g. with nitric acid In combination with a chromatographic separation, speciation is made possible for small 0.5 ml fractions, e.g. for vegetable foodstuffs. For all these applications a multi-element determination can be carried out, for about 20-25 elements simultaneously. Simple and reliable quantification is effected by internal standardization. The reliability of the method has been proved by intercomparison tests. Second-generation instruments that are compact and user-friendly are now commercially available.