Determination of elemental composition of Lake Baikal sponges by wavelength dispersive X‐ray fluorescence spectrometry

Sponge endemic species inhabit the Lake Baikal from the ancient times. Because the sponges are the biological filters of the Baikal water and they contribute greatly to silicon circulation in the lake, it is crucial to analyze their composition. Only a few publications report the analytical data concerning the element composition of Lake Baikal sponges. However, the analytical data were mainly obtained by destructive methods. No data on the concentrations of some alkaline and volatile elements are available so far. This article describes the application of wavelength dispersive X‐ray fluorescence spectrometry to study the sponges of Lubomirskia baicalensis, Baikalospongia bacillifera, and Baikalospongia recta species collected at the littoral part of the Beryozovy Cape in the Southern Baikal. The concentrations of 19 elements Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, and Ba have been determined. In this article, we discuss the problem of selecting calibration samples for wavelength dispersive X‐ray fluorescence spectrometry, because appropriate reference samples are not available. The synthetic specimens, prepared by mixing plant certified reference materials and silicon dioxide in certain proportions, were proposed for calibration. The compositions of sponges cleaned from mineral particles and symbiotic organisms, as well as unwashed sponges, have been compared. Copyright © 2013 John Wiley & Sons, Ltd.     

Trace element determinations in uranium by total reflection X‐ray fluorescence spectrometry using polychromatic X‐ray excitation

Suitability of polychromatic X‐rays has been assessed for the total reflection X‐ray fluorescence (TXRF) trace elemental determinations in aqueous solutions as well as uranium oxide certified reference materials. The method involves total reflection of X‐rays below a certain energy level on the TXRF sample support and exciting the analytes present in ng amount on these supports, measuring the TXRF spectra, processing the spectra, and finally determining the elemental concentrations. For uranium‐based samples, the samples were dissolved, main matrix uranium was separated from these solutions using solvent extraction, and trace elements were determined using aqueous phase following above approach. The method is simple and easier to implement compared with the monochromatic excitation but has similar or in some cases better detection limits compared with those obtained using monochromatic excitation. The details of the methodology, quality of analytical results, and detection limits are described and compared with those obtained using monochromatic excitation. Copyright © 2017 John Wiley & Sons, Ltd.     

Measurement of background components in wavelength dispersive X‐ray fluorescence spectrometry

Three components of the background have been investigated: first, characteristic radiation of the lamellas of the collimator excited by secondary x‐ray beam; second, secondary x‐ray beam scattered by the lamellas of the collimator; third, diffusive and incoherent scattering of the secondary x‐ray beam by the focusing crystal. The relationships between chemical content of the specimen and the intensity of the first and the second components were determined by a wavelength‐dispersive x‐ray spectrometer that has an energy‐dispersive x‐ray detector. The intensity of the third component was very low. It was not found in this experiment. Copyright © 2006 John Wiley & Sons, Ltd.     

Preconcentration of mercury on polyaniline expands the horizon for energy dispersive X‐ray fluorescence determination

Hg(II) was sorbed on polyaniline from aqueous solutions, followed by determination using energy dispersive X‐ray fluorescence spectrometry. Distribution coefficient of Hg(II) on polyaniline was about 4 × 10³ in water, whereas distribution coefficient was 1.2 × 10⁴ at 0.1 M HCl and decreased drastically with increase in HCl concentration. Rapid kinetics of sorption was evinced by the 80% uptake within the initial 1 min and quantitative sorption within 5 min of equilibration. The sorption was found to follow Langmuir isotherm model, and the Langmuir capacity was calculated as 19.7 mg g^?1. The ability of polyaniline to form stable and homogeneous pellets facilitated the energy dispersive X‐ray fluorescence determination without recourse to elution. Detection limit of Hg was found to be 22 ng, considering 100 mg pellet of polyaniline. The apparent detection limit was 6 pg, as the preconcentration factor of Hg(II) on polyaniline was 4 × 10³. The developed method is at par with the established method for mercury determination, namely, cold vapor atomic absorption spectrometry. Accuracy of the method was established by the analysis of the International Atomic Energy Agency reference materials, namely, hair and lichen, for Hg(II). Copyright © 2016 John Wiley & Sons, Ltd.     

Chemical analysis of very small‐sized samples by wavelength‐dispersive X‐ray fluorescence

The chemical characterisation of very small‐sized samples is often of major interest in forensic analysis, studies of artworks, particulate matter on filters, raw materials impurities, and so on, although it generally poses considerable problems owing to the difficulty of obtaining precise and accurate results. This study was undertaken to develop a set of methods for the chemical characterisation of very small‐sized samples by wavelength‐dispersive X‐ray fluorescence. To conduct the study, sample preparation (as beads and pellets) and measurement conditions were optimised to reach the necessary detection and quantification limits and to obtain the appropriate measurement uncertainty for characterising the types of materials involved. The measurements were validated by using reference materials. Three test methods were developed. In two methods, the samples were prepared in the form of beads (one method being for geological materials and the other for the analysis of nongeological materials such as particulate matter on filters, glasses, frits, and ceramic glazes and pigments). In the third method, the samples were prepared in the form of pellets for the analysis of volatile elements in geological materials. In the three methods, detection limits, quantification limits and measurement uncertainties were obtained similar to those found when a bead or pellet is prepared by the usual methods from 0.5 g sample. However, in this study, sample size was between 30 and 40 times smaller in the case of beads and 100 times smaller in the case of pellets, thus broadening the range of possible wavelength‐dispersive X‐ray fluorescence applications in the chemical characterisation of materials. Copyright © 2012 John Wiley & Sons, Ltd.     

The energy dispersive scheme of X‐ray fluorescence analysis with a crystal polarizer and polycapillary optics

The efficiency of the polarization scheme based on polycapillary optics and a diamond crystal polarizer was demonstrated. The scheme provides suppression of the background of scattered radiation in measuring X‐ray fluorescence spectra. A quasi‐parallel X‐ray beam with an angular divergence of 4.2 mrad was formed by a microfocus source with a copper anode and polycapillary half‐lens. Simultaneous polarization and monochromatization of radiation was obtained with a crystal of natural diamond, which was set at the diffraction reflection (113). The degree of polarization of CuK_α1 spectral line and the maximum radiation flux were respectively equal to 99.86% and 5 · 10⁶ photon/s. In the direction orthogonal to the plane of diffraction, the maximum attenuation of the background was up to 19 dB.     

Analysis of engine motor oils by X‐ray absorption and X‐ray fluorescence spectroscopies

The molecular structure of lubricating motor oils is investigated by X‐ray absorption fine structure spectroscopy measurements. Both fresh and used oils are studied. Although the Zn K‐edge spectra gave information about the degradation of the antiwear/antioxidant zinc dialkyl dithiophosphate (ZDDP) additives within the oil, Fe K‐edge spectra are representatives for iron species dispersed in the oil during operation at elevated temperatures and pressures in the engine. The detailed analysis of the measured data shows that substantial differences are detectable in the spectra of the fresh and used oil. Our results show that the Zn–S bonds of the ZDDP are decomposed during the operation, resulting in Zn–O bonds instead. Furthermore, sixfold Fe–O bonds similar to those in Fe₂O₃ are found within the used oil, suggesting the presence of debris from the antiwear film of lubricated motor parts in the used oil. Copyright © 2014 John Wiley & Sons, Ltd.     

Optimized energy dispersive X‐ray fluorescence analysis of atmospheric aerosols collected at pristine and perturbed Amazon Basin sites

Elemental composition of aerosols is important to source apportionment studies and to understand atmospheric processes that influence aerosol composition. Energy dispersive X‐ray fluorescence spectroscopy was applied for measuring the elemental composition of Amazonian atmospheric aerosols. The instrument used was a spectrometer Epsilon 5, PANalytical B.V., with tridimensional geometry that reduces the background signal with a polarized X‐ray detection. The measurement conditions were optimized for low‐Z elements, e.g. Mg, Al, Si, that are present at very low concentrations in the Amazon. From Na to K, our detection limits are about 50% to 75% lower than previously published results for similar instrument. Calibration was performed using Micromatter standards, except for P whose standard was produced by nebulization of an aqueous solution of KH₂PO₄ at our laboratory. The multi‐element reference material National Institute of Standards and Technology–2783 (air particulate filter) was used for evaluating the accuracy of the calibration procedure of the 22 elements in our standard analysis routine, and the uncertainty associated with calibration procedures was evaluated. The overall performance of the instrument and validation of our measurements were assessed by comparison with results obtained from parallel analysis using particle‐induced X‐ray emission and another Epsilon 5 spectrometer. The elemental composition in 660 samples collected at a pristine site in the Amazon Basin and of 1416 samples collected at a site perturbed by land use change was determined. Our measurements show trace elements associated with biogenic aerosols, soil dust, biomass burning, and sea‐salt, even for the very low concentrations as observed in Amazonia. Copyright © 2014 John Wiley & Sons, Ltd.     

Background estimation based on Fourier Transform in the energy‐dispersive X‐ray fluorescence analysis

This paper discusses a new method of background estimation in the energy‐dispersive X‐ray fluorescence (EDXRF) analysis, which is based on Fourier Transform (in this paper, we call it Fourier Transform background estimation method). Compared with the Sensitive Nonlinear Iterative Peak method, the new method has the feature of FWHM independence. It has been proved that a background can be estimated automatically and accurately by the new method in the synthesized spectrum and the spectra from measurement. Fourier Transform background estimation method can estimate the background accurately in the EDXRF spectrum using an X‐ray tube source. Copyright © 2011 John Wiley & Sons, Ltd.     

Using chemometric methods for overlap correction of sodium–zinc spectral lines generated by wavelength dispersive X‐ray fluorescence in mineral samples

Partial least squares, principal component regression and support vector machine multivariate methods were used for overlap correction of sodium–zinc (Na(Kα)–Zn(Lα)) spectral lines generated by means of wavelength dispersion X‐ray fluorescence (WDXRF) combined with standard‐less software (IQ+) technique for the analyses of mineral samples. This methodology uses one scan channel using PX1 analyzer crystal, 550‐µm collimator, flow detector (Ar + CH₄), and rhodium (Rh) tube for determination of Na and Zn in mineral compositions in minimum time. The calibration matrix was made up of 35 samples containing different amounts of Na₂O and ZnO. The considered concentration ranges were 0–5% for both Na₂O and ZnO. The values for 2θ angle were recorded between 25° and 29.9° at every 0.1°. Variable tube powers (kV ? mA) were used to investigate the effect of tube power on the analyses of elements. The validation of the multivariate methods was realized by analyzing soil samples. Atomic absorption and flame photometry methods were used as reference methods for analyzing Zn and Na in the soil samples, respectively. The results of using chemometric methods, WDXRF (standard‐less software) and reference method determined partial least squares and support vector machine models obtained more acceptable results for Na₂O in presence of ZnO than those of WDXRF (standard‐less software). Copyright © 2013 John Wiley & Sons, Ltd.     

Direct multielement determination of Cd,Pb, Fe,and Mn in ground coffee samples using energy dispersive X‐ray fluorescence spectrometry

An analytical method was proposed for the quantification of Cd, Pb, Mn, and Fe in ground coffee samples using energy dispersive X‐ray fluorescence (EDXRF) spectrometry. External calibration was possible using the coffee matrix itself as standards with samples previously analyzed by inductively coupled plasma optical emission spectrometry (ICP OES). The ground coffee samples were analyzed in the form of pellets, which were placed in the center of the EDXRF measuring cell for the determination of the analytes. The limits of detection were 62, 55, 86, and 76 μg/kg for Cd, Pb, Fe, and Mn, respectively. Good linearities were obtained for the calibration curves with coefficients of correlation (R) of 0.9959 for Cd, 0.9939 for Pb, 0.9929 for Fe, and 0.9909 for Mn. Precision, evaluated as the relative standard deviation (RSD) of 10 independent measurements of different cataloged samples with an approximate concentration of 400 μg/kg for each analyte, was between 6 and 14% (n = 10), demonstrating that the preparation of the samples in form of pellets was sufficient to perform analyses by EDXRF. The proposed method was applied in the determination of Cd, Pb, Fe, and Mn in ground coffee samples collected in Salvador, Bahia, Brazil. In a parallel comparative procedure, coffee samples were also analyzed by ICP OES after sample pretreatment by acid digestion. A paired Student's t test was carried out (confidence level of 95%, n = 5) and no significant difference was observed between the concentrations obtained by the proposed and comparative methods.     

Application of energy dispersive X‐ray fluorescence spectrometry for the characterization of plastic materials in synthetic polymer conservation work

Plastic artifacts archived in museums deteriorate with time and require proper care by conservators to prevent their degradation and to maintain the objects in good condition. Degradation processes depend on the type of plastic and conditions of storage. Knowledge of the chemical composition of plastic artifacts is thus very important and facilitates conservation work. The capabilities of energy dispersive X‐ray fluorescence spectrometry with monochromatic excitation were investigated for possible characterization of the plastic materials used in artifacts from museum collections. For this purpose, a simple and suitable nondestructive analytical protocol was developed on the basis of the intensity of the coherent and the incoherent scattered excitation radiation from artifacts, compared with scattering from typical plastic materials such as polyethylene, polyvinyl chloride, and polypropylene. Fifteen plastic artifacts, such as souvenirs, household wares, and toys, were characterized in this way according to their chemical composition. Copyright © 2012 John Wiley & Sons, Ltd.     

Size‐resolved analysis of fine and ultrafine fractions of indoor particulate matter using energy dispersive X‐ray fluorescence and electron microscopy

We used a multistage PIXE inertial impactor with nine different aerodynamic diameter ranges (between 16 and 0.06 μm) to sample indoor particulate matter (PM). X‐ray fluorescence (XRF) measurements performed at cutoff diameters (CoDs) of 0.25, 0.5, 1, 2, 4, and 8 μm were used to identify elements in various size fractions. Anthropogenic sources were the dominant sources for fine and ultrafine particle sizes. The XRF results show that natural sources also contribute to the fine and ultrafine fractions of pollutants. Scanning electron microscopy and energy‐dispersive system analysis were performed on membranes having PM CoDs of 4, 2, 1, 0.5, and 0.25 μm. Elemental mappings show the membranes with PM of CoDs 0.25 and 0.5 μm having S as a dominant element, confirming the results obtained with XRF. Strong correlation among maps of S, N, and O show that ammonium sulfate is the major constituent at these size fractions. Other elements such as Si, Ca, Fe, Al, and Mg show up in smaller amounts at these size fractions but increase for membranes with larger particles. For size fractions larger than 0.5 μm, there is a good correlation between the elemental maps of these elements and oxygen, indicating that these elements exist mostly in oxide forms. The absence of clear N signals and the correlation between the Ca and S maps indicate that S in these size fractions is not due to ammonium sulfate. The presence of Mg, K, Cl, and Na at these CoDs shows that these elements are due to salts originating from sea breeze.     

Determination of effective atomic numbers and mass attenuation coefficients of samples using in‐situ energy‐dispersive X‐ray fluorescence analysis

The matrix effect has a major impact on energy‐dispersive X‐ray fluorescence analysis (EDXRFA) and is difficult to be evaluated due to that the contents of some low‐atomic‐number elements cannot be identified by in‐situ EDXRFA. Up to today, the fundamental parameter algorithm proposed by Rousseau has been widely applied to correct the matrix effect. Accordingly, determining the matrix and mass attenuation coefficient (μ/ρ) of sample is a key issue for the fundamental parameter algorithm. In present work, the method to deduce μ/ρ by effective atomic number (Z_eff) was studied. First, the relationship between Z_eff and coherence to Compton scatting ratio (R) of the incident X‐ray was determined by standard samples. Then, we deduce Z_eff and their μ/ρ. The value of μ/ρ deduced by our method is in good agreement with that calculated by WinXCOM, and the relative change (Δ) is less than 7%. We also deduced Z_eff and their μ/ρ of Chinese national standard soil samples employing our method and good agreement with the calculated values were also obtained. We found that the agreement between experimental values of μ/ρ with theoretical values by WinXCOM still exists when the energy of the incident X‐ray is greater than 4 keV, and the Δ is less than 10%. The result indicates that our method may be applied directly to in‐situ EDXRFA.     

Identification of mineral inclusions in archaeological ceramics using microbeam X‐ray fluorescence spectrometry

Archaeological ceramics are subjected to chemical and geochemical analyses in order to ascertain production techniques and provenance. Many analytical techniques are currently available for the determination of qualitative and quantitative characteristics pertaining to clay composition and structure. Microbeam XRF is utilised in this report to analyse mineral inclusions present in Mleiha ceramics in order to establish better provenance data. A total of 67 mineral inclusions of different sizes and colours were analysed. The majority of the sampled inclusions (94%) were silicates, and only 6% were calcites. A total of 35 inclusions from the former group were olivine minerals composed of a mixture of Mg, Si, and Fe oxides constituting 87–99% of the inclusions' mass, in addition to 13 inclusions composed mainly of Al, Si, and Ca oxides with sum concentrations ranging from 80% to 98%. Copyright © 2014 John Wiley & Sons, Ltd.     

Principal component analysis‐assisted energy dispersive X‐ray fluorescence spectroscopy for non‐invasive quality assurance characterization of complex matrix materials

The analytical challenges in direct quality assurance analysis of complex matrices (extreme matrix effects, spectral overlap, poor signal‐to‐noise ratio (SNR) for trace analytes, ‘dark matrix’, imprecise geometry, need for sample integrity) by energy dispersive X‐ray fluorescence (EDXRF) spectrometry necessitate development of novel techniques for material characterization. We demonstrate the utility of principal component analysis (PCA) in isotope‐excited EDXRF spectrometry of a complex matrix (in this case lubricating oil) in the context of a newly developed EDXRF and scattering (EDXRFS) technique. Lubricating oil quality may be interpreted in terms of its viscosity, anti‐wear, anti‐oxidation, and anti‐rust properties, which are detectable via B, Ca, Mg, Zn, Fe, Na additives (quality markers). Our method involves simultaneous non‐invasive acquisition of both fluorescence and scatter spectra from samples held in a propylene dish, and their modeling in a reduced multidimensional space for an interpretable overview that is analytically more useful than, and complementary to, fluorescence peak‐based quantitation of the additives; by this method, only Fe and Zn are directly detectable, but with SNR of the fluorescence peak 15–20 times poorer compared with analysis after sample digestion. Although Fe and Zn cannot distinguish the various lubricating oil brands, it can differentiate authentic from adulterated. The method was however found to be analytically useful when combined with PCA: various brands of lubricating oil were discriminated in addition to the detection of adulteration. PCA processing of the spectra showed that the most important quality assurance spectral signature information responsible for the success is contained in the scatter region (low‐Z elements). Evaluation of the performance of the method with respect to SNR (i.e. analysis time and therefore speed) showed that there was no significant difference in method performance of analysis live time in the range 100–1000 s, showing proof of concept for rapid characterization of complex matrix materials by PCA‐assisted EDXRFS. Copyright © 2012 John Wiley & Sons, Ltd.     

Artificial peaks in energy dispersive X‐ray spectra: sum peaks,escape peaks,and diffraction peaks

Sum peaks, escape peaks, and diffraction peaks are considered artificial or spurious peaks in energy dispersive X‐ray spectrometry. Experimental examples are given, which showed that escape and diffraction peaks can add up to become sum peaks. These artificial peaks are not weak, and great care must be taken to differentiate them from peaks due to impurity or trace elements. The relationship between the intensity of a sum peak and the original peaks is illustrated using computer simulation as well as probability theory. Copyright © 2016 John Wiley & Sons, Ltd.