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.     

Characterization of homemade x‐ray polycapillaries

The possibilities of performing non‐destructive elemental microanalysis with synchrotron radiation by means of homemade polycapillary optics are described. Using fiber glass technology, monolithic polycapillary half‐lenses were made by drawing packages of glass capillaries at high temperature in a heating furnace. The performance of polycapillary half‐lenses with different geometries was evaluated. A gold knife‐edge scanned at the output of the lenses was used to determine the spot size at different distances. Measurements of photon flux impinging on the entrance end of the lenses and photon flux leaving the lenses were used to obtain the transmission efficiency. The polycapillary half‐lens made in our laboratory was used in a series of XRF microanalysis tests using white beam. The overall efficiency of the system was studied by means of establishing detection limits for various elements in an organic sample. Copyright © 2008 John Wiley & Sons, Ltd.     

The capabilities of an electrically cooled energy‐dispersive x‐ray detector for quantitative x‐ray fluorescence analysis

The capabilities of the Si PIN diode x‐ray detector were determined and compared with those of a standard Si(Li) detector. The x‐ray fluorescence (XRF) analysis systems assembled with these two detectors included annular radioisotope excitation sources of Cd‐109 and Fe‐55. The systems were calibrated for sensitivity and quantification was performed with fundamental parameters software. Based on the analysis of the standard reference material NIST 2710 (Montana soil), the elemental sensitivities and the limits of detection of both systems were obtained. The elemental sensitivities of the Si PIN detector for fluorescence x‐rays in the energy range up to 10 keV were comparable to those of the Si(Li) detector. At higher fluorescence x‐ray energies the sensitivity of the Si PIN detector gradually decreased and was smaller by a factor of ～4 at 20 keV. The reason was mainly the small thickness of the sensitive volume of the Si PIN diode (0.2 mm) and therefore the smaller relative efficiency of this detector. The assessed limits of detection (LODs) were comparable for the two detectors, which was mainly due to the lower spectral background of the Si PIN detector in excitation with the Cd‐109 source as a result of its smaller sensitive thickness. The accuracy of elemental determinations for the two detectors was comparable and within the limits of the assessed uncertainties, which were calculated considering all the steps of the analysis, i.e. spectrum measurement and analysis, sensitivity calibration and quantification. Copyright © 2004 John Wiley & Sons, Ltd.     

Calculation of attenuation and x‐ray fluorescence intensities for non‐parallel x‐ray beams

With the nowadays widespreaded use of x‐ray optics in x‐ray fluorescence analysis, large convergence or divergence angles can occur. This experimental situation violates a basic assumption of the usual fundamental parameter quantification procedure. In order to take beam divergences in micro x‐ray fluorescence analysis into account, a way of calculating fluorescence intensities numerically by Monte Carlo integration is described. For three examples of typical micro‐XRF set‐ups the fluorescence intensities and their deviation from the parallel beam geometry are calculated. Furthermore, we propose a new approach with ‘equivalent angles’ which correct for the beam divergences in fundamental parameter methods. Copyright © 2003 John Wiley & Sons, Ltd.     

Application of selected fundamental parameters in x‐ray fluorescence analysis

The effectiveness of selected fundamental parameters in x‐ray fluorescence analysis previously proposed by the authors was examined with a few examples. Some synthetic fused binary disks were prepared and measured to obtain the measured binary coefficients. The theoretical influence coefficients were also calculated based on the synthetic specimens and measuring conditions using those selected fundamental parameters and compared with the measured values. It was found that the theoretical influence coefficients calculated with selected fundamental parameters agreed better with measured values than those calculated with original parameters. The synthetic fused disks, some Au–Ag–Cu alloys and some Chinese rock reference materials were measured and quantitatively calculated with the program NRLXRF, that uses original parameters, and with NRL301, that uses selected fundamental parameters, using only one calibration standard for fused disks and only pure elements for alloys. The relative errors of the results from NRL301 are much smaller than those from NRLXRF. Data for the example of pressed powders of cement published in an NBS Technical Note were also calculated with NRL301 with one calibration standard. The results are comparable to those from NBSGSC obtained with seven calibration standards. Copyright © 2003 John Wiley & Sons, Ltd.     

Energy‐dispersive x‐ray fluorescence analysis of modern coloured glasses from Marinha Grande (Portugal)

The elemental composition (K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Ba, Nd and Pb) of modern coloured glasses was obtained by energy‐dispersive x‐ray fluorescence (EDXRF) spectrometry. This non‐destructive technique is frequently used in the analysis of historical glass objects. Two reference glasses were also measured to assess the overall accuracy of the EDXRF method. Reference and unknown glasses were analysed without any preparation. The coloured glass samples studied belong to the Glass Museum of Marinha Grande and were chosen from two distinct collections, which were characterized by the different concentrations of some elements (K, Ti, Cr, Mn, Fe, Ba and Pb). The determined major elements allowed the identification of two raw materials used in glass manufacture, sand and lime. Multivariate statistical analysis, namely principal component extraction, simplified the identification of some of the colouring chemical elements, associating them with the different colours of the glass objects. Copyright © 2003 John Wiley & Sons, Ltd.     

Composition determination for complex and transmitting samples in x‐ray quantitative analysis

In this work, quantitative analysis of x‐ray fluorescence measurements of transmitting samples with complex chemical composition is considered. A method is presented for analytical solution of sample composition including matrix effects, independent of sample thickness and requiring no standards. The method uses fundamental parameters and measured fluorescence signal intensities, and is applicable to transmission geometry measurements for which standard analyses are not applicable. Limitations of the analysis presented here are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Experimental observation of frequency tunable x‐rays generated by interaction of nonrelativistic electrons with a silicon crystal

An experimental model of a tunable source of monochromatic x‐rays was developed using nonrelativistic electrons passing through a single crystal silicon target. Theoretical predictions for x‐ray output and characteristics were confirmed experimentally. The distinctive feature of the developed source is the possibility to tune x‐ray frequency at fixed electron beam energy. In the present report, properties and potentialities of the developed source are considered. Copyright © 2007 John Wiley & Sons, Ltd.     

Empirical coefficients models for x‐ray fluorescence analysis of intermediate‐thickness samples

Empirical coefficients models for correction of matrix effects in intermediate‐thickness samples are presented. Two proposed mathematical models correct simultaneously matrix effects and various masses per unit area of the samples. In the first model, it is necessary to know the masses per unit area of the samples and in the second model masses are predicted from the scattered radiation. To calculate coefficients of the models, a series of multi‐element intermediate‐thickness standards with various compositions and various masses per unit area are required. The models were tested experimentally using synthetic samples pressed into pellets and geological certificate reference materials collected on a membrane filter. The calculated concentrations were in good agreement with the certificate values. Copyright © 2004 John Wiley & Sons, Ltd.     

Speeding up of internal excitation calculations and application to x‐ray analysis

An improved calculation method is described for the calculation of internally excited x‐rays. The basis of the method is to express the internal excitation term of a point‐like source by three parameters and to store their precalculated values in a look‐up table. The intensities are taken from this table for the actual values of the parameters instead of calculating them repeatedly on the spot. Therefore, the computational work has been reduced significantly. The results of this calculation are compared with those obtained by standard methods and the speed increment was proved. The method was also tested and validated experimentally for several samples. Copyright © 2004 John Wiley & Sons, Ltd.     

Nanoresolution interface studies in thin films by synchrotron x‐ray diffraction and by using x‐ray waveguide structure

In the last years we performed several measurements with synchrotron radiation of several facilities to reveal interesting interface phenomena on the nanoscale. We used both x‐ray diffraction [1] , [2] (XRD) and spectrometry techniques. In this paper, we briefly summarize the results obtained from diffraction measurements, which lead us to our recent grazing incidence x‐ray fluorescence analysis (GIXRF) and extended x‐ray absorption fine structure (EXAFS) experiments. We show how a combination of experimental methods of GIXRF analysis and EXAFS spectroscopy in fluorescence detection with x‐ray standing waves (XSW) technique was applied for the depth profiling of a‐Si/Co/a‐Si layers with nanometer resolution to monitor the growth of CoSi intermetallic phase. The investigated layers were placed into the waveguide structure formed by two Ta films to increase sensitivity and accuracy of the measurements. Copyright © 2009 John Wiley & Sons, Ltd.     

Micro‐beam x‐ray fluorescence analysis of individual particles with correction for absorption effects

A method of correction for absorption effects in micro‐beam x‐ray fluorescence analysis is described. A fast, energy‐dispersive, silicon drift detector (SDD) was used to measure the primary x‐ray beam transmitted through the sample. The absorption factors were calculated using the data acquired with the SDD. The possibility of using the coherently, incoherently and multiple scattered primary radiation for determining the mass of individual particles was examined. The proposed methods were validated with the use of NIST K3089 glass micro‐spheres of known composition. Copyright © 2006 John Wiley & Sons, Ltd.     

The effects of absorption edge structure of atoms in x‐ray fluorescence analysis

The effects of the absorption edge structure in x‐ray fluorescence (XRF) manifest themselves as a very strong attenuation of the analytical line radiation when it is in the x‐ray absorption near edge structure (XANES) range. In this paper, this effect is exemplified by an ultra‐strong Ba‐caused attenuation of the Ce Lβ₁ line. This case was experimentally studied. Comparison of measured and calculated relative intensities has shown that the actual mass attenuation coefficient of the Ce Lβ₁ line in Ba is 1.6 times greater than known values. This is due to that the Ce Lβ₁ line is within the initial range of L3 Ba absorption edge, i. e. the XANES range. Such an effect of the absorption edge structure of atoms must be considered using the fundamental parameters method in quantitative XRF analysis. This paper also presents some other possible cases of this effect. Copyright © 2009 John Wiley & Sons, Ltd.     

The advantages of using digital signal processing in polarized x‐ray fluorescence analysis

Improving the specificity and productivity of XRF is of great relevance for the determination of trace elements in samples of diverse origin. The advantages of using digital signal processing in energy‐dispersive polarized x‐ray fluorescence analysis are demonstrated by comparing the instrumental sensitivities achieved with those obtained by using a conventional analogue signal processing‐based spectrometer. A compact geometry secondary target arrangement was designed to increase the effective solid angles and to reduce the distances between secondary target, sample and detector, thus achieving larger x‐ray fluxes for both the excitation and detection process, resulting in improved instrumental sensitivities. The performance of both spectrometers was evaluated for two different detectors: an Si(Li) detector and a thermoelectrically cooled passivated‐implanted planar silicon detector (X‐PIPS). The uncertainties achieved and accuracy are illustrated for the analysis of a group of sediment and organic‐origin certified reference materials using two different quantitative procedures. Copyright © 2006 John Wiley & Sons, Ltd.     

Evaluation of metal release from battery and electronic components in soil using SR‐TXRF and EDXRF

Potentially toxic elements may be leached contaminating the soil, surface, and ground water due to the improper disposal of batteries and electronic devices. The objective of this study was to evaluate metal release from batteries and electronic components deposited in specific receptacles filled with soil in which acid rain was simulated. The leachate solution and the soil were analyzed by synchrotron radiation total reflection x‐ray fluorescence and benchtop energy dispersive x‐ray fluorescence, respectively. Results indicate that batteries released K, Mn, Fe, Cu, Zn, and Pb and electronic component released Ti, Mn, Fe, Cu, Zn, and Pb. For batteries' leachate test samples, higher amounts of Fe, Cu, Mn, Zn, and Pb have been released compared with electronic component ones under same the experimental conditions. The Fe, Cu, and Pb concentrations in battery leachate test samples were above their National Environment Council maximum permitted values (MPV) and in the electronic waste leachate ones, only the Pb concentrations was above MPV. For soil sample containing batteries K, Mn and Zn presented higher concentrations, mainly at the 10‐cm topsoil, ranging from 0.16 to 0.50, 0.27 to 8.67, and 0.03 to 1.26, in % (% w/w), respectively. The Zn–C battery soil samples present similar behavior to the alkaline ones. The impact due to the Pb release was higher in the soil test samples with electronic components, in which their concentrations ranged from 51 to 394 mg/kg, above its MPV up to 28‐cm soil layer. The X‐ray fluorescence techniques employed were suitable for water and soil environmental evaluation.     

Characterization of surface carbon films on weathered Japanese roof tiles by soft x‐ray spectroscopy

The effects of weathering on carbon films deposited on Japanese smoked roof tiles were investigated by soft x‐ray absorption and emission spectroscopy using synchrotron radiation. X‐ray absorption measurements revealed that weathering oxidizes the carbon films and that partial carboxy chemical bonding occurs. Incident angle‐dependent x‐ray absorption spectra in the C K region confirmed that the degree of the orientation at the surface of the oxidized carbon films decreases with weathering. However, the take‐off angle‐dependent C K x‐ray emission spectra showed that the orientation of the layered carbon structure is maintained in the bulk portion when weathered. Therefore, it is confirmed that oxidation proceeds from the surface of the carbon films. Weathering degrades and oxidizes the surface carbon films, which causes the metallic silver color to change to darker gray. Copyright © 2005 John Wiley & Sons, Ltd.     

Theoretical influence coefficients for correction of matrix effects in x‐ray fluorescence analysis of intermediate‐thickness samples

Theoretical influence coefficients for x‐ray fluorescence analysis of intermediate‐thickness samples is proposed. The algorithm, derived from the Sherman equation, corrects simultaneously both absorption and enhancement effects in specimens with various thicknesses. The coefficients take into account all matrix elements, hence they have to be calculated using an iterative approach. Nevertheless, if matrix diversification is limited, the coefficients can be treated as constants for given mass per unit area of the specimen. Then the iteration can be avoided and calculations are simple and fast. The dependence of the influence coefficients on matrix composition and sample thickness is discussed. The validity of the proposed algorithm was checked with certified geological materials, four‐element polycrystals and ferroelectric ceramics using wavelength‐dispersive x‐ray spectrometry. Copyright © 2005 John Wiley & Sons, Ltd.     

Signatures of different carbon bonds in graphene oxide from soft x‐ray reflectometry

In graphene oxide, the graphite lattice is intercalated with oxygen groups that bond to carbon atoms. These groups have a bearing on the possibility of using graphene oxide as a precursor to make graphene. The nature of carbon bonds in graphene oxide has been characterized with soft x‐ray reflection spectroscopy across the carbon K‐edge. Results distinguish graphene oxide synthesized with Hummers' method from that made using a method suggested by Tour. The observed spectra are consistent with those from near‐edge x‐ray absorption fine structure (NEXAFS) measurements. In particular, the expected carbon K‐edge resonances associated with excitations into molecular π*‐ and σ*‐states of C? C bonds can be identified. Importantly, the greater oxidation efficiency of the method by Tour may be the reason for the observation of additional resonances that have been assigned to carbon bonding with molecular groups containing oxygen. The additional resonances have been interpreted as the excitations of carbon 1 s electrons into the carbonyl π*(C?O) orbital in the molecular group –COOH and into the hydroxyl π*(C? OH) orbital, respectively. Copyright © 2015 John Wiley & Sons, Ltd.