X-ray Fluorescence Determination Research Articles

Assessing natural contents of hazardous metals in soils by different analytical methods and its impact on environmental legislative measures

A variety of analytical techniques are commonly used to assess natural metal concentrations in soils. Although the choice of the analytical procedure may appear to be an unimportant issue, through an example from the Po Plain we document that for specific hazardous metals the arbitrary choice between separate analytical techniques may have contrasting legislative implications. Comparative analyses of 160 soil samples obtained with X-ray Fluorescence (XRF) and aqua-regia Inductive Coupled Plasma Mass Spectrometry (ICP-MS), respectively, reveal a systematic lower efficiency of chromium determination by ICP-MS (45–60% of XRF determinations), irrespective of the laboratory chosen. Maximum permissible concentrations of chromium for residential and recreational sites were invariably exceeded by sediments deriving from chromium-rich parent rocks after XRF analyses. In contrast, replicate determinations following aqua regia digestion were generally below the threshold values, defining the same soils as unpolluted. This study thus emphasises the need for strictly standardised procedures of metal determination.

X-ray fluorescence analysis of Ni–Fe–Mn/Cr systems

We have developed a procedure for x-ray fluorescence determination of the constituent composition and thickness of two-layer Ni–Fe–Mn/Cr films deposited on Polikor, an aluminum oxide ceramic. We have calculated correction coefficients taking into account interelement interference effects in this system. We have experimentally determined the density of the materials making up the composition of the films. We have established and present the metrological characteristics of the procedure developed.

Partial least squares X-ray fluorescence determination of trace elements in sediments from the estuary of Nerbioi-Ibaizabal River

The feasibility of partial least squares (PLS) regression modeling of X-ray fluorescence (XRF) spectra of estuarine sediments has been evaluated as a tool for rapid trace element content monitoring. Multivariate PLS calibration models were developed to predict the concentration of Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, V and Zn in sediments collected from different locations across the estuary of the Nerbioi-Ibaizabal River (Metropolitan Bilbao, Bay of Biscay, Basque Country). The study was carried out on a set of 116 sediment samples, previously lyophilized and sieved with a particle size lower than 63 μm. Sample reference data were obtained by inductively coupled plasma mass spectrometry. 34 samples were selected for building PLS models through a hierarchical cluster analysis. The remaining 82 samples were used as a test set to validate the models. Results obtained in the present study involved relative root mean square errors of prediction varying from 21%, for the determination of Pb at hundreds μg g −1 level, up to 87%, for Ni determination at little tens μg g −1 level. An average prediction error of ±37% for the 14 elements under study was obtained, being in all cases mean differences between predicted and reference results of the same order than the standard deviation of three replicates from a same sample. Residual predictive deviation values obtained ranged from 1.1 to 3.9.

Energy dispersive X-Ray fluorescence determination of thorium in phosphoric acid solutions

Energy dispersive X-ray fluorescence studies on determination of thorium (in the range of 7 to 137 mg/mL) in phosphoric acid solutions obtained by dissolution of thoria in autoclave were made. Fixed amounts of Y internal standard solutions, after dilution with equal amount of phosphoric acid, were added to the calibration as well as sample solutions. Solution aliquots of approximately 2–5 µL were deposited on thick absorbent sheets to absorb the solutions and the sheets were presented for energy dispersive X-ray fluorescence measurements. A calibration plot was made between intensity ratios (Th Lα/Y Kα) against respective amounts of thorium in the calibration solutions. Thorium amounts in phosphoric acid samples were determined using their energy dispersive X-ray fluorescence spectra and the above calibration plot. The energy dispersive X-ray fluorescence results, thus obtained, were compared with the corresponding gamma ray spectrometry results and were found to be within average deviation of 2.6% from the respective gamma ray spectrometry values. The average precision obtained in energy dispersive X-ray fluorescence determinations was found to be 4% (1 σ). The energy dispersive X-ray fluorescence method has an advantage over gamma ray spectrometry for thorium determination as the amount of sample required and measurement time is far less compared to that required in gamma ray spectrometry.

Approaches to improving the accuracy in X-ray fluorescence analysis of Si1 − x Ge x films

This work examines approaches to improving the accuracy in the X-ray fluorescence determination of the composition and thickness of thin Si1 − xGex films on Polikor alumina substrates. We calculate correction coefficients that take into account the interelement effects in the films and demonstrate the possibility of reaching the required accuracy level in determining film composition and thickness. The results are used to optimize conditions for the preparation of films with tailored electrical properties.

Energy dispersive X-ray fluorescence determination of cadmium in uranium matrix using Cd Kα line excited by continuum

An energy dispersive X-ray fluorescence method for determination of cadmium (Cd) in uranium (U) matrix using continuum source of excitation was developed. Calibration and sample solutions of cadmium, with and without uranium were prepared by mixing different volumes of standard solutions of cadmium and uranyl nitrate, both prepared in suprapure nitric acid. The concentration of Cd in calibration solutions and samples was in the range of 6 to 90 µg/mL whereas the concentration of Cd with respect to U ranged from 90 to 700 µg/g of U. From the calibration solutions and samples containing uranium, the major matrix uranium was selectively extracted using 30% tri-n-butyl phosphate in dodecane. Fixed volumes (1.5 mL) of aqueous phases thus obtained were taken directly in specially designed in-house fabricated leak proof Perspex sample cells for the energy dispersive X-ray fluorescence measurements and calibration plots were made by plotting Cd Kα intensity against respective Cd concentration. For the calibration solutions not having uranium, the energy dispersive X-ray fluorescence spectra were measured without any extraction and Cd calibration plots were made accordingly. The results obtained showed a precision of 2% (1 σ) and the results deviated from the expected values by < 4% on average.

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.

X-ray fluorescence determination of the macroscopic composition of As-S, As-Se, and As-S-Se glasses

An X-ray fluorescence technique has been developed for determination of the macroscopic composition of As-S-Se, As-S, and As-Se chalcogenide glasses. Reference samples for calibration have been prepared by direct elemental synthesis. The calibration error has been estimated.

X‐ray fluorescence determination of the FeO/Fe2O3tot ratio in igneous rocks

AbstractThis study was performed to search for the possibility of assessing the FeO/Fe2O3tot ratio in rocks using K‐ and L‐series of the X‐ray fluorescence (XRF) spectrum. The uncertainty in the determination of the FeO/Fe2O3tot ratio was compared from the obtained ratios of Kβ2, 5‐/Kβ1, 3‐ and Lβ‐/Lα1, 2‐line intensities. The measurements were implemented by a conventional XRF spectrometer, S4 Pioneer. The assessment of the uncertainty in FeO/Fe2O3tot determination in mineral powder fractions proved that the Kβ2, 5/Kβ1, 3 ratio of lines could be selected as the analytical signal. A relative standard deviation of FeO content in the collection of 48 reference materials of igneous rocks varies within the range of 5–16%, depending on the range of the FeO/Fe2O3tot ratio and the FeO content. The best accuracy was attained for FeO/Fe2O3tot &gt;0.45 with FeO contents varying within 5–15%. In the andesite and basalt samples, the relative standard deviation was &lt;4%. In granite rocks, the error reached 23% at fairly low content of FeO &lt;3%. For the igneous rock samples at a ratio FeO/Fe2O3tot &gt;0.25, the XRF determination of FeO content can be performed at an accuracy comparable with that of wet chemical analysis. The XRF method is preferred because it is fast and convenient for sample preparation. It could be used as an analytical technique in routine geochemical investigations. Copyright © 2009 John Wiley &amp; Sons, Ltd.

High-sensitivity X-ray fluorescence analysis of solutions with the use of a sorption accumulation microsystem

A mass-transfer kinetic model is proposed for an embedded sorption accumulation microsystem based on polycapillary structures to be used in the developed X-ray fluorescence analyzer with preconcentration. The model is used to substantiate a kinetic method for high-sensitivity X-ray fluorescence determination of elements in multicomponent solutions. With the use of this model, experimental data on X-ray fluorescence spectra are analyzed and kinetic and equilibrium parameters are found for the sorption of copper, nickel, manganese, iron, and zinc on the selective DETATA sorbent.

X-ray Fluorescence Determination of Element Contents in Milk and Dairy Products

The concentrations of minerals (Na, Mg, P, S, Cl, K, and Ca) and trace elements (Mn, Fe, Ni, Cu, Zn, Rb, Sr, and Br) in different types of milk, dairy products, and infant formulas have been determined using wavelength-dispersive X-ray fluorescence analysis (WDXRF). Freeze-dried samples pressed as tablets of 4 g have been analyzed. Calibrations have been established using both plant and milk standard reference materials. The matrix correction method based on the power function of Compton scattered intensity was applied. The paper provides calibration data, detection limits for each element, and testing the accuracy of the proposed technique. The elemental compositions of the samples obtained by WDXRF were compared with the previously reported data from different countries.

Determination of rhenium in gold-containing ores by X-ray fluorescence spectrometry

A procedure is developed for determining rhenium in gold-containing ores by X-ray fluorescence spectrometry. The adsorption preconcentration of perrhenate ions on activated charcoal is studied. It is found that the pH of the solution, the time of exposing the adsorbent to the solution, UV irradiation, and the presence of associate elements (tungsten, gold, silver, and copper) affect the adsorption. The procedure is applied to the X-ray fluorescence determination of rhenium in gold-containing ores from different deposits.

Characteristics of Picoliter Droplet Dried Residues as Standards for Direct Analysis Techniques

The characteristics of dried residues of picodroplets of single-, two-, and three-element aqueous solutions, which qualify these as reference materials in the direct analysis of single particles, single cells, and other microscopic objects using, e.g., laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS) and micro-X-ray fluorescence (MXRF), were evaluated. Different single-, two-, and three-element solutions (0.01-1 g/L) were prepared in picoliter volume (around 130 pL) with a thermal inkjet printing technique. An achievable dosing precision of 4-15% was calculated by total reflection X-ray fluorescence (TXRF) determination of the transferred elemental mass of an array of 100 droplets. The size of the dried residues was determined by optical microscopy to be 5-20 microm in diameter depending on the concentration and the surface material. The elemental distribution of the dried residues was determined with synchrotron micro-X-ray fluorescence (SR-MXRF) analyses. The MXRF results show high uniformity for element deposition of every single droplet with an RSTD of 4-6% depending on the concentration of spotted solution. The shape and height profile of dried residues from picoliter droplets were studied using atomic force microscopy (AFM). It was found that these dry to give symmetrical spherical segments with maximum heights of 1.7 microm. The potential of this technique for direct LA-ICP-TOF-MS analysis is shown.

Sorption and X-ray fluorescence determination of trace elements in water using quasi-solid radiators

Thin-film (based on polyvinyl alcohol) and gel-like (based on gelatin) radiators for an X-ray fluorescence analysis of carbon sorbates containing oxinates of copper and nickel have been developed. We have studied principal characteristics of sorption processes. Lower boundaries of concentrations of copper determined in aqueous solutions constitute 0.05 and 1.5 mg/dm3 respectively for film and gel-like radiators, while that of nickel using film radiators—0.01 mg/dm3.

X-ray fluorescence determination of bromine in halogenated organic compounds using quasisolid emitters

A series of quasi-solid emitters is proposed for the X-ray fluorescence determination of bromine in different bromine-containing compounds. It is shown that sucrose-based glasses are the best emitters for analyzing alkali solutions of halogenated organic compounds, saccharose-based glasses and polymer films are best for analyzing powder samples, and organic gels offer most promise for analyzing liquid (at normal conditions) samples. It is noted that the proposed method can expand the possibilities of commercially produced element analyzers, which are currently intended for determining only C, H, O, N, and S in organic compounds and cannot be used for determining halogens.

X-ray fluorescence determination of the molar ratio of metals in heterobimetallic complexes

A method was developed for the X-ray fluorescence determination of the molar ratio of metals in heterobimetallic complexes. The procedure includes simple rapid sample preparation and a novel algorithm of measurements and data processing. It was demonstrated that the procedure can be also used for the determination of the metal ratio in films of complexes applied to oxide supports.

Quantification of zinc–porphyrin in dry-cured ham products by spectroscopic methods: Comparison of absorption, fluorescence and X-ray fluorescence spectroscopy

Zinc–protoporphyrin (Zn–pp), which has been identified as the major pigment in certain dry-cured meat products, was extracted with acetone/water (75%) and isolated from the following meat products: Parma ham, Iberian ham and dry-cured ham with added nitrite. The quantification of Zn–pp by electron absorption, fluorescence and X-ray fluorescence (XRF) spectroscopy was compared (concentration range used [Zn–pp] = 0.8–9.7 μM). All three hams were found to contain Zn–pp, and the results show no significant difference among the content of Zn–pp quantified by fluorescence, absorbance and X-ray fluorescence spectroscopy for Parma ham and Iberian ham. All three methods can be used for quantification of Zn–pp in acetone/water extracts of different ham types if the content is higher than 1.0 ppm. For dry-cured ham with added nitrite, XRF was not applicable due to the low content of Zn–pp (<0.1 ppm). In addition, XRF spectroscopy provides further information regarding other trace elements and can therefore be advantageous in this aspect. This study also focused on XRF determination of Fe in the extracts and as no detectable Fe was found in the three types of ham extracts investigated (limit of detection; Fe ⩽ 1.8 ppm), it allows the conclusion that iron containing pigments, e.g., heme, do not contribute to the noticeable red colour observed in some of the extracts.

X-Ray fluorescence determination of trace toxic metals with extraction and preconcentration on silica gel chemically modified with mercapto groups

The sorption properties of silica gel with γ-mercaptopropyl groups chemically immobilized on its surface toward Pb(II), Cd(II), and Zn(II) at MPC levels in natural water in Ukraine were studied. The mutual effect of Pb(II), Cd(II), and Zn(II) in the sorption-X-ray fluorescence determination of their trace amounts with preextraction on silica gel with γ-mercaptopropyl groups was examined

X-ray fluorescence determination of sulfur and other elements in customs control of oil and liquid oil products

Results of an X-ray fluorescence determination of sulfur and other elements in oils and liquid oil products are presented, obtained using a Spectro-Xepos energy-dispersive spectrometer with the excitation of the fluorescence spectrum immediately in the liquid samples under investigation. It is shown that the amount of trace elements considerably varies not only in different types of oil products, but also in different samples of the same product. An experimental evaluation of the metrological characteristics of the determination of sulfur in oil products showed that they met the requirements of GOST (Russian State Standard) R 50442-92 Oil and Oil Products: X-ray Fluorescence Method for Determining Sulfur.

Adsorption of Toxic Metal Ions onto Silica with Covalently Bound 8-Hydroxyquinoline

8-Hydroxyquinoline covalently bound to silica via a one-stage Mannich reaction was used as an adsorbent for the pre-concentration of Pb(II), Cd(II), Zn(II) and Mo(VI) ions from aqueous solutions in the dynamic mode following determination of their concentrations by X-ray fluorescence methods. The adsorption of Pb(II), Cd(II), Zn(II) and Mo(VI) ions was studied from individual and complex multi-component solutions of both natural and technogenic origins. Peculiarities associated with the simultaneous X-ray fluorescence determination of mixtures of toxic metal ions in a solid matrix are discussed.