Wavelength dispersive X‐ray fluorescence (WDXRF) and chemometric investigation of human hair after cosmetic treatment

Variations in the chemical composition of 63 different human and 6 different synthetic hair samples were investigated using wavelength dispersive X‐ray fluorescence (WDXRF) spectra profiles. To evaluate the effect of cosmetic treatment on the strands, the human hair samples were bleached, but the synthetic ones were not. To better investigate the data, exploratory analyses were calculated using principal component analysis for the WDXRF spectra. Eight normalizations/standardizations were applied in the WDXRF to verify the clustering tendency. Bleaching was tested, because it is one way in which people mask their real hair color. After the data were standardized, an enhancement of the data discrimination was verified. Furthermore, the explained variance was higher in the first principal components. The WDXRF spectra were able to distinguish samples with distinct features, including synthetic, dyed, and straightened hair. The findings of this study hold promise for forensics due to desirable aspects such as nondestructivity and the possibility of a large hair sample database.     

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.     

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.     

X‐ray tube spectral measurement method for quantitative analysis of X‐ray fluorescence analysis

Lα and Lβ X‐ray fluorescence spectra of a lead metallic sheet were measured using an energy dispersive X‐ray spectrometer by changing the X‐ray tube voltage and the material of the primary filter. The Lα to Lβ intensity ratio changed from Lα: Lβ = 3: 1 at 15 kV to Lα: Lβ = 1: 1 at 50 kV depending on the X‐ray tube voltage and the filter. The scattered X‐ray spectra of an acrylic slab instead of the sample in the sample holder were measured by changing the applied voltage and the material of the primary filter. The calculated values of the Pb Lα/Lβ intensity ratio of the metallic sheet using the Shiraiwa–Fujino formula by inserting the scattered X‐ray spectra of an acrylic plate as incident X‐ray spectra and the fundamental parameters taken from the Elam database were in good agreement with the experimental ones. We conclude that we can obtain an incident X‐ray spectrum approximately by measuring the scattered X‐ray spectrum without measuring the direct incident beam. Copyright © 2010 John Wiley & Sons, Ltd.     

Valence‐to‐core X‐ray emission spectroscopy of titanium compounds using energy dispersive detectors

X‐ray emission spectroscopy (XES) of transition metal compounds is a powerful tool for investigating the spin and oxidation state of the metal centers. Valence‐to‐core (vtc) XES is of special interest, as it contains information on the ligand nature, hybridization, and protonation. To date, most vtc‐XES studies have been performed with high‐brightness sources, such as synchrotrons, due to the weak fluorescence lines from vtc transitions. Here, we present a systematic study of the vtc‐XES for different titanium compounds in a laboratory setting using an X‐ray tube source and energy dispersive microcalorimeter sensors. With a full‐width at half‐maximum energy resolution of approximately 4 eV at the Ti Kβ lines, we measure the XES features of different titanium compounds and compare our results for the vtc line shapes and energies to previously published and newly acquired synchrotron data as well as to new theoretical calculations. Finally, we report simulations of the feasibility of performing time‐resolved vtc‐XES studies with a laser‐based plasma source in a laboratory setting. Our results show that microcalorimeter sensors can already perform high‐quality measurements of vtc‐XES features in a laboratory setting under static conditions and that dynamic measurements will be possible in the future after reasonable technological developments.     

A fast energy‐dispersive multi‐element detector for X‐ray absorption spectroscopy

In this paper results are presented from fluorescence‐yield X‐ray absorption fine‐structure spectroscopy measurements with a new seven‐cell silicon drift detector (SDD) module. The complete module, including an integrated circuit for the detector readout, was developed and realised at DESY utilizing a monolithic seven‐cell SDD. The new detector module is optimized for applications like XAFS which require an energy resolution of ～250–300 eV (FWHM Mn Kα) at high count rates. Measurements during the commissioning phase proved the excellent performance for this type of application.     

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.     

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.     

A novel method for resonant inelastic soft X‐ray scattering via photoelectron spectroscopy detection

A method for measuring resonant inelastic X‐ray scattering based on the conversion of X‐ray photons into photoelectrons is presented. The setup is compact, relies on commercially available detectors, and offers significant flexibility. This method is demonstrated at the Linac Coherent Light Source with ～0.5 eV resolution at the cobalt L₃‐edge, with signal rates comparable with traditional grating spectrometers.     

A three‐crystal spectrometer for high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy and X‐ray emission spectroscopy at SSRF

A Johann‐type spectrometer for the study of high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy, X‐ray emission spectroscopy and resonant inelastic X‐ray scattering has been developed at BL14W1 X‐ray absorption fine structure spectroscopy beamline of Shanghai Synchrotron Radiation Facility. The spectrometer consists of three crystal analyzers mounted on a vertical motion stage. The instrument is scanned vertically and covers the Bragg angle range of 71.5–88°. The energy resolution of the spectrometer ranges from sub‐eV to a few eV. The spectrometer has a solid angle of about 1.87 × 0^?3 of 4π sr, and the overall photons acquired by the detector could be 10⁵ counts per second for the standard sample. The performances of the spectrometer are illustrated by the three experiments that are difficult to perform with the conventional absorption or emission spectroscopy. Copyright © 2016 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.     

Feasibility of in‐line instruments for high‐resolution inelastic X‐ray scattering

Inelastic X‐ray scattering instruments in operation at third‐generation synchrotron radiation facilities are based on backreflections from perfect silicon crystals. This concept reaches back to the very beginnings of high‐energy‐resolution X‐ray spectroscopy and has several advantages but also some inherent drawbacks. In this paper an alternate path is investigated using a different concept, the `M⁴ instrument'. It consists of a combination of two in‐line high‐resolution monochromators, focusing mirrors and collimating mirrors. Design choices and performance estimates in comparison with existing conventional inelastic X‐ray scattering instruments are presented.     

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.     

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.     

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.     

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.     

Methodology for the determination of minor and trace elements in petroleum cokes by wavelength‐dispersive X‐ray fluorescence (WD‐XRF)

This article describes a methodology for the analysis of minor and trace elements in petroleum cokes by wavelength‐dispersive X‐ray fluorescence (WD‐XRF) spectrometry. The methodology was developed in order to have a rapid and reliable control method of these elements, because they determine coke end uses. There are a number of standard methods of chemical analysis by WD‐XRF or inductively coupled plasma atomic emission spectrometry (ICP‐OES) techniques. However, the standards that use WD‐XRF measurement give detection limits (L_D) above 10 mg·kg^?1 and only analyse a few elements of interest, whereas the ICP‐OES method requires extensive sample handling and long sample preparation times, with the ensuing errors. In order to improve the method described in the standard ASTM D6376 and reach the L_D and quantification limits (L_Q) required, the different stages of the process, ranging from sample preparation to measurement conditions: analytical line, detector, crystal, tube power, use of primary beam filters, and measurement time, were optimised. The samples were prepared in the form of pressed pellets, under conditions of high cleanliness of the mills, crushers, presses, and dies, and of the laboratory itself. The following reference materials were used in measurement calibration and validation: SRM 1632c, SRM 2718, SRM 2719, SRM 2685b, AR 2771, AR 2772, SARM 18, SARM 19, and CLB‐1. In addition, a series of materials were analysed by WD‐XRF and ICP‐OES, and the results were compared. The developed methodology, which uses WD‐XRF, is rapid and accurate, and very low L_D and measurement uncertainties were obtained for the following elements: Al, Ba, Ca, Cr, Cu, Fe, Ge, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, V, and Zn. Copyright © 2010 John Wiley & Sons, Ltd.