Mathematical techniques for quantitative elemental analysis by energy dispersive X-ray fluorescence

Recent interest in the use of automated or semi-automated energy dispersive X-ray fluorescence analysis has created the need for improved mathematical techniques and computer software for use with this type of analysis. The present paper reviews the efforts to date to develop the mathematical techniques necessary for implementing: (1) the library least-squares method for the determination of characteristic elemental X-ray intensities and (2) the use of the Monte Carlo method for extending the fundamental parameters approach to radioisotope and X-ray machine exciting sources for the determination of elemental amounts.     

Total-reflection X-ray fluorescence analysis for semiconductor process characterization

Semiconductor process characterization techniques based on total-reflection X-ray fluorescence (TXRF) analysis are reviewed and discussed. One of the most critical factors in obtaining reliable determinations by TXRF is the reliability of the standard samples that are used. Conventional physisorption standard samples such as spin coat wafers have two potential drawbacks: reproducibility of depth profile and stability. A method of chemisorption called ‘immersion in alkaline hydrogen peroxide solution (IAP)’ was proposed that provides answers to these two problems. IAP standard samples were used to experimentally examine three methods of TXRF application: Straight-TXRF, VPD-TXRF, and Sweeping-TXRF. In the application of Straight-TXRF, the linearity of Cu at a level of 10⁹ atoms cm⁻² is examined. In the application of VPD-TXRF, test results of VPD-TXRF for both transition metals and light elements are shown. Finally, a new measurement protocol called Sweeping-TXRF is proposed to conduct whole-surface analysis without chemical preconcentration.     

Macromolecules by total reflection X-ray fluorescence: marking techniques

This paper proposes an optimized method to mark polysaccharide macromolecules with heavy atoms in order to make possible their detection by total reflection X-ray fluorescence. A chemical reaction was employed to produce the substitution of OH groups of the polymer macromolecules by iodine atoms. Temperature, time, concentration of reactants and pH of the labeling chemical reaction were the variables and the relative sensitivities of the introduced atoms in the TXRF determinations were the optimization parameters for the TXRF determinations. Control of the physical properties of the polymer and the labeled product were made in order to prevent chemical alterations. The quantification of the labeled macromolecules was made by a previous careful calibration.     

Determination of nickel in lateritic ore by various techniques of energy dispersive X-ray fluorescence analysis

Radiometric techniques of determining the nickel content in lateritic ore samples are described. In some of the methods proposed a semiconductor detector and a multichannel pulse height analyzer are required. In another technique simple portable equipment with a proportional counter was used. Calculation methods of correction for matrix effects were applied, in combination with measurements of the fluorescence to scatter ratio and the use of edge filters.     

Specific features of X-ray fluorescence analysis techniques using capillary lenses and synchrotron radiation

This paper discusses the features of an application of two versions of X-ray fluorescence analysis (XRF), commonly used at present, namely XRF using synchrotron radiation to excite the fluorescence in the sample investigated (SRXRF), and XRF using capillary X-ray optics. The operational characteristics of different models of micro-XRF spectrometers are considered. The general differences between conventional XRF and SRXRF and their influence on the choice of the analytical procedure are also presented. Examples of the typical errors resulting from the use of some classical analytical procedures in several applications are illustrated.     

Detection limit calculations for the total reflection techniques of X-ray fluorescence analysis

In this work, theoretical calculations of detection limits for different total reflection techniques of X-ray fluorescence analysis are presented. Calculations include grazing incidence (TXRF) and gracing emission (GEXRF) conditions. These calculations are compared with detection limits calculated for conventional X-ray fluorescence (XRF). In order to compute detection limits, Shiraiwa and Fujino's model was used to calculate X-ray fluorescence intensities. This model makes certain assumptions and approximations to achieve the calculations, especially in the case of the geometrical conditions of the sample, and the incident and takeoff beams. Nevertheless, the calculated data of detection limits for conventional XRF and total-reflection XRF show a good agreement with previous results. The model proposed here allows us to analyze the different sources of background and the influence of the excitation geometry, which contribute to a better understanding of the physical processes involved in the XRF analysis by total reflection. Finally, a comparison between detection limits in total-reflection analysis at grazing incidence and at grazing emission is carried out. Here, a good agreement with the theoretical predictions of the Reciprocity Theorem is found, showing that, in theory, detection limits are similar for both techniques.     

Chemical characterization of particulate matter suspended in the atmosphere by energy dispersive X-ray fluorescence (EDXRF)

Summary This paper presents the first measurement of the elemental composition of the suspended particulate matter in the atmosphere of Londrina city (Paraná State, Brazil). The sampling was accomplished in the summer of 2003 and in the winter of 2002, with a stacker filter holder, collecting simultaneously the fine particulates (PM_2.5) and the coarse particulates (PM₁₀). The concentration of K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br and Pb associated with particulate matter was determined by energy dispersive X-ray fluorescence. The results of the grouping analysis suggested that the elements in the aerosol particles came from two sources: soil re-suspension and industrial or anthropogenic activities.     

Enrichment procedures for small quantities of metals by organometallic and other coprecipitation techniques for X-ray fluorescence analysis

Summary Enrichment procedures for small quantities of metals by organometallic and other coprecipitation techniques for X-ray fluorescence analysis were studied. In order to obtain a higher X-ray intensity and good reproducibility in the measurements, five requirements were considered for the precipitants and for the precipitate. Favourable organic precipitants are mainly alizarine blue, phenyl fluorone, and cupferron, good inorganic precipitates were fluorides and reduced metals. Other precipitation procedures can be applied to some metal elements, if the precipitation reaction is selective and a higher X-ray intensity is obtained.

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Anreicherungsverfahren für Spurenelemente durch Mitfällung in Form organischer Komplexe und anderer Verbindungen für die röntgenspektroskopische Analyse

Zusammenfassung Verschiedene Anforderungen werden beschrieben, die an ein verbessertes Anreicherungsverfahren gestellt werden. Als ausgezeichnete Fällungsmittel erwiesen sich Alizarinblau, Phenylfluoron und Kupferron. Zweckmäßige anorganische Niederschläge sind Fluoride und reduzierte Metalle. Andere Fällungsverfahren werden für einige Elemente benutzt, wenn die Reaktionen selektiv sind und die Röntgenintensität höher ist.

     

Study on deposition kinetics of high-K materials by X-ray fluorescence techniques

X-ray fluorescence (XRF) techniques have been used to study, on different pretreated substrates, deposition kinetics of HfO₂ and Al₂O₃, two of the possible high-K materials under evaluation for future integration in microelectronic devices.X-ray fluorescence (XRF) and total X-ray fluorescence (TXRF) measurements demonstrate their capability to give useful information on the very initial growing cycles of deposition and on carbon and chlorine inclusion in the film. Moreover, XRF signal shows a good linear correlation with layer thickness for thick samples of both materials.     

Chemical state analysis of fluorine in various compounds using X-ray fluorescence spectra

F Kα X-ray fluorescence (XRF) spectra of various fluorides were measured and to investigate the chemical state of fluorine in xHoF₃-20BaF₂-10AlF₃-(70 − x)GeO₂ (mol%, x = 10-50) glass. The main peak (Kα_1,2) position and the relative intensity of the satellite peak attributable to Kα_3,4 were discussed relating to the M-F bond covalency. Results showed that the fluorine in xHoF₃-20BaF₂-10AlF₃-(70 − x)GeO₂ (mol%, x = 10-50) glass had a completely different chemical state from that of starting materials. Quantitative analyses of the glasses were also undertaken using XRF measurements for each component. These results suggest that 30% fluorine in the 50HoF₃-20BaF₂-10AlF₃-20GeO₂ system is substituted by oxygen through pyrohydrolysis of the fluorides.     

X-ray fluorescence analysis of rocks

Summary Modern methods for the determination of various elements in geological materials by XRFA are reviewed. XRFA theory and metrological characteristics are discussed in detail.

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Röntgenfluorescenzanalyse von Gesteinen

     

Soil characterization by energy dispersive X-ray fluorescence: sampling strategy for in situ analysis.

This work describes a sampling strategy that will allow the use of portable EDXRF (energy dispersive X-ray fluorescence) instruments for "in situ" soil analysis. The methodology covers a general approach to planning field investigations for any type of environmental studies and it was applied for a soil characterization study in the zone of Campana, Argentina, by evaluating data coming from an EDXRF spectrometer with a radioisotope excitation source. Simulating non-treated sampled as "in situ" samples and a soil characterization for Campana area was intended. "In situ" EDXRF methodology is a powerful analytical modality with the advantage of providing data immediately, allowing a fast general screening of the soil composition.     

Preparation and characterization of chloroaluminum phthalocyanine-loaded solid lipid nanoparticles by thermal analysis and powder X-ray diffraction techniques

Solid lipid nanoparticles (SLN) without drug and SLN loaded with chloroaluminum phthalocyanine (AlClPc) were prepared by solvent diffusion method in aqueous system and characterized by thermal analyses and X-ray diffraction (XRD) in this study. Determination of particle size, zeta potential (ZP), and encapsulation efficiency were also evaluated. SLN containing AlClPc of nanometer size with high encapsulation efficiency and ZP were obtained. The results indicated that the size of SLN loaded with AlClPc is larger than that of the inert particle, but ZP is not changed significantly with incorporation of the drug. In differential scanning calorimetry (DSC) curves, it was observed that the melting point of stearic acid (SA) isolated and in SLN occurred at 55 and 64 °C, respectively, suggesting the presence of different polymorphs. DSC also shows that the crystallinity state of SLN was much less than that of SA isolated. The incorporation of drug in SLN may have been favored by this lower crystallinity degree of the samples. XRD techniques corroborated with the thermal analytic techniques, suggesting the polymorphic modifications of stearic acid.     

Identification of steel by X-ray fluorescence analysis with a pyroelectric X-ray generator

An application of X-ray fluorescence analysis with a pyroelectric X-ray generator is presented. Steel standard samples were identified by X-ray fluorescence analysis with this novel X-ray generator to check its capability for performing qualitative and quantitative analysis as an X-ray source for X-ray fluorescence spectrometers. Cr, Ni, V, Co, and W were detected in steel standard samples. V and Cr can be detected even when the content is below 1%. Although it is difficult to detect minor elements because of the low power of the excitation X-rays, it is possible to identify the analyzed samples on the basis of major elements at the percentage level. The pyroelectric X-ray generator is very suitable for portable X-ray fluorescence spectrometers.     

Analysis of high-temperature superconducting films by X-ray fluorescence analysis

Radionuclide X-ray fluorescence analysis was used for the determination of Cu, Y and Ba in very thin high-temperature superconducting films. The precision of the method is better than 3% for about 1 m thick films. The atomic emission ICP spectrometry was used to testify results of XRF analysis. An acceptable agreement of both methods was obtained.     

Elemental analysis of special materials by X-ray fluorescence spectrometry

The special materials like phosphor bronze for P, Fe, Ni, Cu, Zn, Sn and Pb; mild steel for P, S, V, Cr, Mn, Co, Ni, Cu, As, Nb, Sb and W; special alloys for Ti and Mo, zircaloy and zirconium oxide for Hf; and zircon ore for Zr have been analyzed by X-ray fluorescence spectrometry (XRFS). The measured values along with certified values, precision and accuracy have been given for all the elements analyzed. Some of these materials have also been analyzed by atomic absorption spectrometry (AAS), neutron activation analysis (NAA) and inductively coupled plasma emission spectrometry (ICP-ES). The analytical data of XRFS are in agreement with the results obtained by AAS-ICP-ES and NAA. In most cases the precision is within ±2% and accuracy is ±4%. The precision and accuracy for S, P, Ni and Hf are poor at low concentrations. Practical low detection limit of about 40 g/g of Hf in zirconium matrix has been achieved. It is established that precise and accurate determination of Ti and Mo in special alloys is possible using XRFS.     

Non-destructive analysis of archeological samples by energy-dispersive X-ray fluorescence

Summary A non-destructive method is described for the determination of major and minor constituents in archeological specimens by energy-dispersive X-ray fluorescence. Homogeneity tests are made by measuring at various sites of the specimen. In the same way, mean values are obtained for inhomogeneous specimen without taking samples. For calibration, powder standards are used. In case of the determination of elements with numbers up to 14 (Si) a vacuum chamber is used and the dimensions of the specimens are limited by the dimensions of that vacuum chamber, whereas for the determination of elements from K up to U specimens of any size, form or weight are suitable.

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Zerstörungsfreie Analyse von archäologischen Proben mit Hilfe der Energie-dispersiven Röntgenfluorescenzanalyse

Zusammenfassung Eine zerstörungsfreie Methode für die Bestimmung von Haupt- und Nebenbestandteilen in archäologischen Proben mit Hilfe der Energie-dispersiven Röntgenfluorescenzanalyse wird beschrieben. Für Homogenitätstests wird an mehreren Stellen der Probe gemessen. In der gleichen Weise werden für inhomogene Proben Mittelwerte erhalten ohne Probenahme. Für die Eichung werden Pulverstandards verwendet. Im Falle der Bestimmung von Elementen mit Ordnungszahlen bis 14 (Si) wird eine Vakuumkammer eingesetzt, und die Dimensionen der Proben sind durch die Dimensionen dieser Vakuumkammer begrenzt, während für die Bestimmung der Elemente K bis U Proben jeder Größe, jeder Form oder jeden Gewichts verwendbar sind.

     

X射线荧光光谱分析

作为《分析试验室》定期评述“X射线荧光光谱分析”系列评论第八篇,本文收集国内学者在1998年7月至2000年6月期间公开发表在国内外期刊和国际会议文集上的129篇论文,并对此期间对我国X射线荧光光谱分析的概况、发展和国际上的地位进行了讲述,内容包括仪器及维修、基体校正、数据处理方法、谱分析方法的研究、标样及样品制备、全反射X射线荧光光谱、同步辐射光源X射线荧光光谱、粒子激发X射线发射、X射线荧光光谱分析方法研究及其应用。