Spatially resolved X-ray fluorescence analysis with a pyroelectric X-ray emitter.

A portable instrument for two-dimensional X-ray fluorescence imaging was assembled with an X-ray source using a pyroelectric crystal, which was driven by a 9-V dry battery, a Si-PIN detector, a slit, and pulse motors. Line scanning for a mug and a knife-edge-scan of an iron sheet were carried out using this spectrometer. The sensitivity of the spectrometer was sufficient for elemental analysis of a mug using a 1 mm(2) slit, and several elements, such as Co, Ni, Zn, Pb and Zr, were detected. The estimated spatial resolution using a 0.8-mm pinhole was 3.5 mm.     

Error of sample preparation in pressing emitters for X-ray fluorescence analysis

When determining element concentrations in geological samples by X-ray fluorescence spectrometry using emitters obtained by pressing tablets from powder samples, we revealed the effect of a significant difference in line intensities of characteristic long-wavelength emission (ΔI _i) from opposite sides of the emitter. The effects of compacting pressure, mass of emitter, and its surface area on ΔI _i were investigated. It was shown that the account of this effect can reduce the error of sample preparation in using compacting pressures lower than 20 t.     

Electro-deposition as a sample preparation technique for total-reflection X-ray fluorescence analysis

A one-step sample preparation by electro-deposition for total-reflection X-ray fluorescence (TXRF) analysis has been developed using a common three-electrode arrangement with a rotating disc as the working electrode. Several elements such as Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, Pb, As and U have been determined simultaneously in saline matrix. A special electrode tip has been constructed as a holder for the TXRF sample carrier, which consists of polished glassy carbon. The influence of parameters such as time, pH value, and trace element concentration on the deposition yield has been examined for 14 elements. From repeatability studies, the uncertainty in deposition yields at the 95% confidence level has been found to be less than 20% for most of these elements. Typical detection limits range from 5 to 20 ng/l under the experimental conditions applied here. By an appropriate choice of the reference element and by calculation of yield factors, reliable quantification can be achieved directly by internal standardization. First results obtained for the standard reference material CRM 505 are presented.     

X-ray fluorescence spectrometry analysis for minerals with agaron gel for sample preparation

A mineral sample preparation with agaron gel used in X-ray fluorescence analysis was developed. Mineral samples were decomposed with aqua-regia. The sample solution mixed with agaron gel was heated to boiling and then it would become quasi-solid gel under normal temperature. The elements dispersed in gel medium could be detected by X-ray fluorescence spectrometry. The method has both advantages of the solution preparation method and the solid preparation method. In addition, this method was adapted in detecting high content ores due to its' avoiding the risk of using platinum crucibles. The method has been applied to the determination of lead, zinc and iron in zinc and lead concentrates successfully.     

Improvement of matrix effects correction in X-ray fluorescence analysis through the optimum relation

A computer program for the optimization of relation for correction of matrix effects in Energy Dispersive X-Ray Fluorescence (EDXRF) analysis is described Program functioning and correction efficiency is studied experimentally in the case of silicate geological samples.     

X-ray Peltier cooled detectors for X-ray fluorescence analysis

The recent results on development of X-ray Si(Li), Si-planar and CdTe p-i-n detectors cooled by Peltier coolers for fabrication of laboratory and portable XRF analysers for different applications are discussed.

Low detection limits of XRF analysers are provided by increasing of detectors sensitive surface; improvement of their spectrometrical characteristics; decreasing of front-end-electronics noise level; Peltier coolers and vacuum chambers cooling modes optimization.

Solution of all mentioned tasks allowed to develop Peltier cooled detectors with the following performances:

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Advantages and disadvantages of all types of detectors for X-ray fluorescence analysis are compared. Spectra are presented. Application of different XRF analysers based on developed detectors in medicine, environmental science, industry, cryminalistics and history of art are demonstrated.     

Radioisotope sources for X-ray fluorescence analysis

Problems involved in developing radioisotope sources and the characteristics of potentially useful radioisotopes for X-ray fluorescence analysis are presented. Some of the isotopes, which are not in use but look very promising, are indicated.     

Development of a procedure for the determination of X-ray fluorescence of metals in aerosols

The precision of the determination of the of heavy metals in aerosols by X-ray fluorescence after their collection on a paper filter is evaluated depending on the chemical composition and weight of unsaturated samples. Recommendations on the choice of the optimal shape of the calibration function and on the conditions for the determination of its coefficients used for the X-ray analysis of unsaturated samples are formulated. A procedure for the X-ray determination of metals in aerosols collected on paper filters is developed; its performance characteristics are presented.     

Contribution to the sample preparation in the radionuclide X-ray fluorescence analysis of hair

Methods of sample treatment in XRF analysis of hair are studied in view of the effect on analytical results. A new method is proposed based on the incomplete ashing of hair followed by pellet preparation. Its suitability is estimated on the XRF analysis of real hair samples collected from 4 healthy adults.     

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

     

Optimisation of total-reflection X-ray fluorescence for aerosol analysis

The capabilities of total-reflection X-ray fluorescence (TXRF) analysis were investigated to develop an efficient, simple, rapid and low cost analytical method for aerosols. The technique involves direct impaction of airborne particulate matter on the quartz sample-reflector discs for TXRF. Special attention was paid to bounce-off effects, and hence the aerosol size distributions for the impactor stages; influence of siliconizing the quartz discs on the adhesion of particles; choice of the internal standard; local distribution of the material deposited on the quartz disc; and alternative materials for aerosol collection. Moreover, the proposed method could be used in combination with a one-stage impactor for total aerosol mass collection and analysis.     

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。     

Sample preparation for evaluation of detection limits in X-ray fluorescence spectrometry.

The influence of analyte mass concentration on determination of detection limits in X-ray fluorescence spectrometry has been investigated experimentally. Both the total reflection X-ray fluorescence (TXRF) and the conventional energy-dispersive X-ray fluorescence techniques have been used to derive the dependence of analyte mass concentration on the values of detection limits. Results obtained indicate that values of detection limits are optimum, or in other words, they are closer to the true detection limit of the technique, when analyte concentrations are in the range of 10 times of the detection limit.     

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.     

X-ray fluorescence analysis of titanium alloys

An X-ray solution method is proposed for determining major amounts of Mo, Sn and Zr in Ti alloys. The method utilizes adjacent elements in the periodic table as internal standards and has been successfully applied to levels of 3-10% Sn, 11-40% Mo and 6-20% Zr. The procedure involves three steps: dissolving the sample with a suitable acid mixture; adding the suitable internal standard at the concentration levels experimentally found to give optimum accuracy and precision; analysing the resulting solution mixture by X-ray fluorescence. Antimony was found to be a suitable internal standard for its adjacent element tin at a concentration ratio of 3:1 Sb:Sn. Niobium was successfully used for both its adjacent elements, molybdenum and zirconium, at 2:1 concentration ratios, Nb:Mo and Nb:Zr. A number of elements non-adjacent to tin, molybdenum and zirconium (i.e., copper, bromine, titanium, bismuth and tantalum) were experimentally found unsuitable as internal standards. Concentration factors of the internal standard and the adjacent elements sought were found to affect significantly the precision of analysis.     

X-ray fluorescence analysis of polymetallic ores

An analytical procedure for determination of Fe, Ti, V, Ni, Co and Cu, the most important constituents of the polymetallic ore has been developed. Twenty four powdered samples were prepared from the material taken in various places of the ore deposit. The samples were analyzed by wavelength dispersive (WD) and energy dispersive (ED) XRF method. The EDXRF method was applied using radioisotope source as well as a low power X-ray tube (Rh-anode) for excitation of the characteristic K-line radiation of the elements. A Si(Li) detector was used for the detection of radiation. The detection limits and precision of the analytical procedures, using reference materials, were estimated. The accuracy of the different XRF techniques is discussed. The developed analytical procedures based on the XRF method are rapid and quite simple. They can be useful for exploration data accumulation.     

X-ray fluorescence analysis of multiple-layer films

Theoretical equations for fluorescent count rates from bulks, single-layer films, and multiple-layer film specimens, based on fundamental parameter models, are developed. Absorption and secondary enhancement within each layer, between layers, and between layers and substrate are considered. A computer program is used to predict count rates as well as for simultaneous back-calculation of concentrations and thicknesses. Standards can be bulks, single films, or multiple films in any combination; pure-element standards as well as those containing additional elements are suitable. Evaluation of experimental data from two- and three-layer films (by using bulk pure-element standards) by the proposed method shows agreement with <0.3%(absolute) for concentrations and <5%(relative) for thicknesses compared to results from single-layer reference specimens prepared under identical conditions.     

Surface analysis for Si-wafers using total reflection X-ray fluorescence analysis

Summary Total Reflection X-Ray Fluorescence Analysis is presented as a novel analytical tool for the determination of metal impurities on Si-Wafer surfaces [1]. This method allows accurate quantification of surface coverages down to 10¹¹ atoms/cm² in a non-destructive way. The technique uses a molybdenum tube, a Si(Li) detector, and instrumentation for the exact control of the angle of incidence which must be set to a particular value below the cricitical angle for total reflection with an accuracy better than 0.1 mrad. Advantages are the lack of sample preparation and vacuum. Standards for quantification can be easily produced. Repeatability tests on three different wafers show good variability even for low concentrations.

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Oberflächenanalyse für Si-Wafer mit Hilfe streifend einfallender Röntgenstrahlen

     

Development of suitable plastic standards for X-ray fluorescence analysis

For the adoption of the EU directive “Restriction on use of certain Hazardous Substances” and “Waste Electrical and Electronic Equipment” using X-ray fluorescence analysis suitable standard materials are required.     

Effect of the conditions of sample preparation for x-ray fluorescence analysis on the effect of microabsorption heterogeneity

The dual effect of the microabsorption heterogeneity (MAH) of emitters on the fluorescence intensity (I _fl) is shown on the basis of the literature data. The duality is due to the covering of large fluorescent grains by small filler particles (II type effect) and its absence (I type effect). For some materials, the effect of MAH can change not only in magnitude but also in sign. It is shown experimentally that the prediction of the covering effect is difficult. It was found that, upon crushing multicomponent materials, different granulometric fractions differ in their chemical composition. This makes the theoretical account of the effect of the MAH of the emitter on the results x-ray fluorescence analysis hardly probable. It is shown that the experimental account by means of radiation scattered (I _σ) or absorbed (I _ab) by the sample possible only in a particular case, because the dependences I _fl,I _σ, and I _ab on the particle size differ in nature.