Total Reflection X-ray Fluorescence Determination Research Articles

Total-reflection X-ray fluorescence determination of thorium and uranium in the presence of interfering elements in solid geological objects of natural and technogenic origin

The insufficient spectral resolution of the energy-dispersive total-reflection X-ray fluorescence (TXRF) complicates the U and Th Lα lines using for the quantitative determination of low concentrations of these elements in natural solid samples.

Simultaneous determination of Os, Ir, Pt and Au in sorbent phases by total reflection X-ray fluorescence

Simultaneous determination of trace and ultra-trace noble metal (NM) contents is a challenging analytical problem. Quantification of NMs in a solid sorbent phase by total reflection X-ray fluorescence (TXRF) was propounded to exclude the problematic stage of analytes desorption. In this study, line overlapping and spectra processing were discussed, theoretical upper limit of area-related mass of the sorbent on a reflector was evaluated, and different quantification procedures were compared. A procedure for the simultaneous determination of Os, Ir, Pt and Au in the solid sorbent phase was developed. This procedure includes sorption of NMs from a diluted solution of a digested sample, TXRF determination of analytes directly in the sorbent phase and data processing using empirical calibration or multivariate regression algorithms (principal component regression, projection on latent structures or partial least squares regression). The procedure allows determining Os, Ir, Pt, Au with a relative error of 15%. Calculated limits of quantification (LOQ) for rocks, considering our sample decomposition procedure, were equal to 0.43, 0.39, 0.43 and 0.31 μg g−1 for Os, Ir, Pt and Au, respectively. The procedure was verified using certificated reference materials and ICP-MS as a reference method.

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

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

Direct Multielemental Trace Determinations in Plutonium Samples by Total Reflection X-ray Fluorescence Spectrometry Using a Very Small Sample Amount.

A simple, safe, and sensitive method for direct multielemental trace determinations in plutonium samples using total reflection X-ray fluorescence (TXRF) spectrometry has been developed. A very small volume (2 μL) of the sample solutions was deposited on TXRF supports after separation of the plutonium matrix from these solutions. Since the amount of the plutonium deposited on the supports was in the ng level only fixed on the supports and the specimen spots were not disturbed during the sample preparation, the samples could be analyzed directly without putting the instrument in a glovebox. This approach avoided a cumbersome operation of the instrument in a glovebox, which is normally utilized for Pu-based samples using other techniques. Similarly, the requirement of small amounts of the samples minimized the radiation dose to the operator as well as a cumbersome problem of management of radioactive analytical waste of plutonium samples. The samples were analyzed using the TXRF spectra of the specimens, concentration of the internal standard Se or Ga and predetermined sensitivity values. The elemental detection limits for the elements K-Sr varied from 1.06 to 0.09 ng. The elements K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Ba, Tl, and Pb were analyzed at μg/mL level. The analytical results of TXRF determinations showed average relative standard deviation (RSD) value of 4.5% (1σ, n = 3) and the TXRF determined results deviated from the expected values by 5.9% on average for samples prepared by adding multielements in plutonium solutions. Two real plutonium samples were also analyzed in similar manner. For the real plutonium sample solution the average RSD values of TXRF determinations were 10.6% (1σ, n = 3) for the elemental concentrations in the range of 0.2 to 61 μg/mL. These values are comparable with conventional trace element analytical techniques with added advantages mentioned above.

Determination of Mercury(II) in Drinking Water by Total Reflection X-ray Fluorescence Spectrometry and Liquid–Liquid Microextraction

ABSTRACTThe total reflection X-ray fluorescence determination of mercury(II) in drinking water at concentrations of 7 × 10−2 to 3.0 µg/L is reported. The mercury(II) preconcentration protocol includes directly suspended droplet microextraction with benzene as a molecular iodine complex. The proposed approach is highly selective. The elements Cr, Mn, Fe, Co, Ni, Zn, and Pb at concentrations up to 0.1 g/L did not interfere with the extraction of trace mercury(II). The method is characterized by high sensitivity (limit of detection of 21 ng/L) and suitable reproducibility (relative standard deviation of 0.12 for 100 ng/L). The accuracy of the results was confirmed by recovery and the method of standard addition.

Total reflection X-ray Fluorescence determination of interfering elements rubidium and uranium by profile fitting

Systematic studies to assess the analytical parameters obtained in the total reflection X-ray fluorescence (TXRF) determinations of interfering elements Rb and U using profile fitting are reported in the present manuscript. The X-ray lines Rb Kα and U Lα having serious spectral interference (ΔE=218eV), have been used as analytical lines. The intensities of these X-ray lines have been assessed using profile fitting. In order to compare the analytical results of Rb determinations in presence of U, with and without U excitation, synchrotron radiation was tuned to energy just above and below the U Labs edge. This approach shall excite both Rb Kα and U Lα simultaneously and Rb Kα selectively. Finally, the samples were also analyzed with a laboratory based TXRF spectrometer. The analytical results obtained in all these conditions were comparable. The authenticity of the results was assessed by analyzing U with respect to Rb in Rb2U(SO4)3, a standard reference material for U. The average precision obtained for TXRF determinations was below 3% (RSD, n=3, 1σ) and the percent deviation of TXRF values from the expected values calculated on the basis of sample preparation was within 3%.

A comparative study on the total reflection X-ray fluorescence determination of lowZelements using X-ray tube and synchrotron radiation as excitation sources

Detailed total reflection X-ray fluorescence (TXRF) studies for the detection and quantification of low atomic number elements were carried out by using a laboratory dual source TXRF spectrometer equipped with a vacuum chamber and at the International Atomic Energy Agency multi-purpose end-station facility, operated at the XRF beamline of Elettra Sincrotrone Trieste, Italy. Multi-elemental standard aqueous solutions of low Z elements (F, Na, Al, S, K, Sc, and Ti) with different elemental concentrations of 2, 10, 20, and 30 µg/ml were prepared and measured in both setups. The measurements at the synchrotron setup were performed in a scanning mode across the sample residue and perpendicular to the incident beam in order to account properly for a possible non-uniform deposition of certain elements. The accuracy and the detection limits obtained from the TXRF measurements in both setups were determined and comparatively evaluated and assessed. Significant improvement in the TXRF detection limits at the synchrotron beamline end-station was obtained for the elements with Z ≤ 13 (Al). Copyright © 2017 John Wiley & Sons, Ltd.

Total reflection X-ray fluorescence determination of rare earth elements in mineral water

A method is proposed for determination of lanthanum, cerium, praseodymium, neodymium, and samarium in mineral water by means of total-reflection X-ray fluorescence analysis. In this work, the combined technique of preconcentration of rare earth ions is used. This technique consists of coprecipitation of metal hydroxides on the collector (iron (III) hydroxide) and dispersive liquid–liquid microextraction of their complexes with 1-(2-pyridylazo)-2-naphthol by chloroform in the presence of ethanol. The use of the developed hybrid approach allows simultaneous determination of the mentioned metals in mineral water in the range n(10–2–101) μg/L. The results of analysis of Arkhyz and Rychal-Su mineral waters by the proposed extraction–X-ray fluorescent method are confirmed by the literature data, obtained by inductively coupled plasma mass spectrometry.

TXRF intensity dependence on position of dried residue on sample carrier and TXRF determination of halogen in liquid samples

Total reflection X‐ray fluorescence (TXRF) spectroscopy is an effective technique for simultaneous multi‐elemental trace analysis of a small volume of a sample placed on a flat substrate. An internal standard method is usually applied for quantitative TXRF analysis of liquid samples such as drinking water and environmental samples. However, it was difficult to determine Cl and Br because they were lost as volatile hydrogen halide compounds by adding an acid internal standard solution. Thus, we attempted to apply the traditional calibration curve method for the determination of halogens without internal standard. If internal standard method is not applied, the TXRF intensity drastically changes depending on the relative position of the dried residue to the detector. Therefore, we investigated the relationship between TXRF intensity and the position of dried residue relative to the detector. As a result, it was confirmed that TXRF intensity critically depended on the position of the dried residue on the sample carrier. The position of the droplet of the sample solution was carefully controlled by using an air blower in order to place the dried residue at the most effective position on the sample carrier. We could successfully make a calibration curve for Cl with a good relationship without internal standard. Finally, Cl in the NaCl solutions (0 –5 ppm, 10 µl) was successfully determined by the calibration curve method using a table‐top TXRF instrument. The limit of detection of Cl was 63 ppb (ng/ml). Copyright © 2016 John Wiley & Sons, Ltd.

A comparative study on total reflection X-ray fluorescence determination of low atomic number elements in air, helium and vacuum atmospheres using different excitation sources

A comparison of trace element determinations of low atomic number (Z) elements Na, Mg, Al, P, K and Ca in air, helium and vacuum atmospheres using W Lβ1, Mo Kα and Cr Kα excitations has been made. For Mo Kα and W Lβ1 excitations a Si (Li) detector with beryllium window was used and measurements were performed in air and helium atmospheres. For Cr Kα excitation, a Si (Li) detector with an ultra thin polymer window (UTW) was used and measurements were made in vacuum and air atmospheres. The sensitivities of the elemental X-ray lines were determined using TXRF spectra of standard solutions and processing them by IAEA QXAS program. The elemental concentrations of the elements in other solutions were determined using their TXRF spectra and pre-determined sensitivity values. The study suggests that, using the above experimental set up, Mo Kα excitation is not suited for trace determination of low atomic number element. Excitation by WLβ1 and helium atmosphere, the spectrometer can be used for the determination of elements with Z=15 (P) and above with fairly good detection limits whereas Cr Kα excitation with ultra thin polymer window and vacuum atmosphere is good for the elements having Z=11 (Na) and above. The detection limits using this set up vary from 7048pg for Na to 83pg for Ti.

Determinations of low atomic number elements in real uranium oxide samples using vacuum chamber total reflection x-ray fluorescence

Conditions for the total reflection x-ray fluorescence (TXRF) analysis of real uranium samples for low atomic number elements using vacuum chamber TXRF spectrometer were optimized. It was observed that for analysis of low atomic number elements, almost complete removal of uranium matrix is required. Two certified reference materials of uranium containing trace elements in different concentrations were dissolved in minimum amount of high purity nitric acid. The uranium matrix from these solutions was separated by solvent extraction using tri-n-butyl phosphate as extracting reagent. Low atomic number elements in TXRF spectrum of the aqueous phase could be seen only after six tri-n-butyl phosphate equilibrations in extraction. The TXRF determinations of the certified low atomic number elements Mg and Al were made in these aqueous solutions after addition of Sc as an internal standard. The TXRF determined values for Mg were in good agreement with the certified values, whereas TXRF determined Al values differed from the certified values appreciably, probably due to the interference of Al Kα peak with escape peak of U Mα and the neighboring Si Kα peak. Copyright © 2013 John Wiley & Sons, Ltd.

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.

Forensic application of total reflection X-ray fluorescence spectrometry for elemental characterization of ink samples

The possibility of applying Total Reflection X-ray Fluorescence for qualitative and quantitative differentiation of documents printed with rare earth tagged and untagged inks has been explored in this paper. For qualitative differentiation, a very small amount of ink was loosened from the printed documents by smoothly rubbing with a new clean blade without destroying the manuscript. 50 μL of Milli-Q water was put on this loose powder, on the manuscript, and was agitated by sucking and releasing the suspension two to three times with the help of a micropipette. The resultant dispersion was deposited on quartz sample support for Total Reflection X-ray Fluorescence measurements. The Total Reflection X-ray Fluorescence spectrum of tagged and untagged inks could be clearly differentiated. In order to see the applicability of Total Reflection X-ray Fluorescence for quantitative determinations of rare earths and also to countercheck such determinations in ink samples, the amounts of rare earth in painted papers with single rare earth tagged inks were determined by digesting the painted paper in HNO 3/HClO 4, mixing this solution with the internal standard and recording their Total Reflection X-ray Fluorescence spectra after calibration of the instrument. The results thus obtained were compared with those obtained by Inductively Coupled Plasma Mass Spectrometry and were found in good agreement. The average precision of the Total Reflection X-ray Fluorescence determinations was 5.5% (1 σ) and the average deviation of Total Reflection X-ray Fluorescence determined values with that of Inductively Coupled Plasma Mass Spectrometry was 7.3%. These studies have shown that Total Reflection X-ray Fluorescence offers a promising and potential application in forensic work of this nature.

A novel approach for chlorine determination in acidic medium by total reflection x‐ray fluorescence

AbstractA novel approach for chlorine (Cl) determination in acidic medium using total reflection x‐ray fluorescence (TXRF) is reported. It is based on the addition of a known excess amount of AgNO3 solution to the sample containing Cl for precipitating silver chloride (AgCl). This is followed by TXRF determination of Ag in supernatant after filtering, employing Cd as an internal standard. Tungsten (W) continuum excitation at 50 kV and 38 mA was used for TXRF measurements. Ag Kα line of the analyte, Ag and Cd Kα line of the internal standard, Cd were used for such determinations of Ag. Six samples of NaCl were prepared in HNO3 medium of different molarities to obtain the Cl concentrations ranging from 1 to 60 µg/ml. The precision of such TXRF determinations of Cl in nitric acid medium samples was found to be better than 10% (1σ) and the results deviated from the expected Cl concentrations by less than 15%. An overall laboratory and reagents blank of 1.5 ± 0.5 µg/ml was obtained limiting the applicability of this approach to Cl levels of about 5 µg/ml. This can be improved by using ultra clean laboratory and high purity reagents. Copyright © 2009 John Wiley & Sons, Ltd.

Trace element determination in thorium oxide using total reflection X-ray fluorescence spectrometry

Applicability of Total Reflection X-ray Fluorescence (TXRF) spectrometry for the determination of trace metals at concentration of µg/g level in thorium oxide was studied. The TXRF spectrometer was calibrated using a multielement standard solution and the method was validated by analyzing another multielement standard solution. Sample preparation conditions were optimized for the TXRF determinations of trace metals in thorium oxide. The elements K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Ba and Pb present in thorium oxide standards were determined after dissolving them in HNO 3/HF mixture and separating the bulk matrix, thorium, by solvent extraction using tri- n-butyl phosphate (TBP) and tri- n-octyl phosphine oxide (TOPO) as extractants. A comparison of TXRF determined concentrations of trace elements Ca, V, Cr, Mn, Fe, Ni and Cu with the certified values shows that TXRF determined concentrations have an RSD of 20% (1 s for n = 4) and are within an agreement of 20% of the certified values in most of the cases.

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.