Study of biofilm formation by total-reflection X-ray fluorescence spectrometry

A total reflection X-ray fluorescence spectrometric method was developed for elemental analysis of natural biofilms grown on polycarbonate substrates in the Lake Velence. For the duration of 9 weeks long growing period, two substrates were removed weekly from the lake and investigated by analytical and algological methods. The total biomass production achieved its highest value after 7 weeks. Ca, Sr and Ti, as well as Fe, Mn, K and Zn showed their maximum concentrations in the biofilms after 5 and 6-7 weeks, respectively. The enrichment factors of the 6 weeks old biofilm for the detected seven elements amounted to 10³-10⁴. The recommended colonization time for biomonitoring of the Lake Velence is 6 weeks applying polycarbonate substrates.     

Application of total-reflection X-ray fluorescence spectrometry in material analysis

X-ray fluorescence spectrometry with total reflection conditions is applied in the qualitative and quantitative determination of impurities in thin layers of Ti, TiO₂, and HfO₂ prepared by evaporation and of SiO₂, TiO₂, and Ta₂O₅ prepared by ion beam sputtering. The same method is used to examine stainless steel discs, which have to be used as reference materials,Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Determination of metal-cofactors in enzyme complexes by total-reflection X-ray fluorescence spectrometry

The determination of metal-cofactors and their molar concentrations is an important requirement for the characterisation of metalloproteins and a challenge regarding the capabilities of trace analytical methods. In this respect, total-reflection X-ray fluorescence spectrometry offers many advantages for the determination of trace elements in enzymes, as compared to other well known analytical techniques such as flame atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry (ICP-AES), because of the significantly smaller amounts of sample required. Without any decomposition, elements like P, S, Fe, Ni, Cu, Zn, Mn and Mo could be determined with high accuracy, in spite of the large bio-organic matrix. The enzymes (polysulphide reductase and hydrogenase of the rumen bacterium Wolinella succinogenes, and the cytochrome c oxidase and quinol oxidase of the soil bacterium Paracoccus denitrificans) were transferred from their usual salt-buffer into a solution of 100 mmol l⁻¹ tris(hydroxymethyl)aminomethane (tris)-acetate containing an appropriate detergent. By this procedure, an improved signal-to-noise ratio is obtained. The polysulphide reductase was found to contain copper as a hitherto existing unknown cofactor. The enzyme contains a stretch of amino acids that are typical of copper proteins and thus confirm the presence of this element. Furthermore, the data concerning cytochrome c oxidase from Paracoccus denitrificans are in good agreement with published values obtained by ICP-AES. Also, results from measurements with the quinol oxidase from the same bacterium agree with the expected values. The investigations lead to the conclusion that the method is well suited to the quantitative determination of metals in enzymes, in particular their molar fractions, and requires only small amounts of the biological sample without any extensive pretreatment. © 1997 Elsevier Science B.V.     

Study of archaeological ceramics by total-reflection X-ray fluorescence spectrometry: Semi-quantitative approach

Total-reflection X-ray fluorescence spectrometry has been compared with Instrumental Neutron Activation Analysis in order to test its potential application to the study of archaeological ceramics in the archaeometric field. Two direct solid non-chemical sample preparation procedures have been checked: solid sedimentation and solid chemical homogenization. For sedimentation procedure, total-reflection X-ray fluorescence allows the analysis of the elemental composition with respect to the size fraction but not the average evaluation of the composition. For solid chemical homogenization procedure, total-reflection X-ray fluorescence provides precise (from 0.8% to 27% of coefficient of variation) and accurate results (from 91% to 110% of recovery) for 15 elements (Cr, Hf, Ni, Rb, Al, Ba, Ca, K, Mn, Ti, V, Cu, Ga, Y and Fe) with an easy sample preparation process of the solid clay and without previous chemical treatment. The influence of the particle sizes has been checked by total-reflection X-ray fluorescence sample angle scans and anomalous behaviors have been found for three additional detected elements: As, Sr and Zn, which can be attributed to interference effects of the mineral grain sizes of their associated chemical phases in the total-reflection X-ray fluorescence interference region. The solid chemical homogenization procedure produces data useful for archaeological interpretation, which is briefly illustrated by a case-study. Finally, the decantation procedure data can be also useful for size chemical speciation and, consequently, for alternative environmental total-reflection X-ray fluorescence applications.     

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.     

Determination of trace elements in the water cycle by total-reflection x-ray fluorescence spectrometry

The determination of trace elements in the various stages of the water cycle is very important. Economic procedures for multi-element determinations of trace elements in various matrices are needed. The applications of total-reflection x-ray fluorescence spectrometry in this general area are reviewed briefly, with examples relating to rain, river and sea waters, sediments, particulate matter and manganese nodules and crusts, as well as mussel tissue. Up to 25 elements can be determined; these are S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Pb, Se, Rb, Sr, Y, Zr, Mo, Ag, Cd, Sb and Ba. Preliminary treatments of the various matrices are described. Accuracy checks by analysis of reference standards and by application of independent techniques are reported.     

Determination of metal-cofactors in respiratory chain complexes by total-reflection X-ray fluorescence spectrometry (TXRF)

Total Reflection X-Ray Fluorescence Spectrometry (TXRF) offers many advantages for the detection of trace elements in enzymes as compared to other well known analytical techniques like flame-AAS or ICP-AES because of the significantly smaller amounts of sample required. Without any decomposition, elements like Fe, Ni, Cu, Zn, Mn and Mo could be determined with high accuracy, in spite of the large bio-organic matrix. Besides the metals also sulfur can be determined in protein samples. The two terminal oxidases, cytochrome c oxidase and quinol oxidase, isolated from the soil bacterium Paracoccus denitrificans, were transferred from their usual salt buffer into a solution of 100 mmol/L tris(hydroxymethyl)aminomethane (TRIS) acetate containing an appropriate detergent. By this procedure an improved signal/noise ratio is attained. The data for cytochrome c oxidase are in good agreement with values obtained by ICP-AES. Further results of quinol oxidase, which has different element ratios, also fit the expected values. The investigations lead to the conclusion that the method is well suited for the quantitative determination of metals in enzymes, and in particular their molar ratios, and requires only small amounts of the biological sample without any extensive pretreatment. Received: 17 June 1997 / Revised: 21 November 1997 / Accepted: 27 November 1997     

Calibration of reference materials for total-reflection X-ray fluorescence analysis by heavy ion backscattering spectrometry

Total-reflection X-ray fluorescence (TXRF) is widely used for the control of metallic contamination caused by surface preparation processes and silicon materials. At least three companies supply a variety of TXRF systems to the silicon integrated circuit (IC) community, and local calibration of these systems is required for their day to day operation. Differences in local calibration methods have become an issue in the exchange of information between IC manufacturers' different FABs (Fabrication Facility) and also between silicon suppliers and IC FABs. The question arises whether a universal set of fluorescence yield curves can be used by these different systems to scale system sensitivity from a single element calibration for calculation of elemental concentrations. This is emphasized by the variety of experimental conditions that are reported for TXRF data (e.g. different angles of incidence for the same X-ray source, different X-ray sources, etc.). It appears that an instrumental factor is required. We believe that heavy ion backscattering spectrometry (HIBS) provides a fundamental method of calibrating TXRF reference materials, and can be used in calculating this instrumental factor. In this paper we briefly describe the HIBS system at the Sandia National Laboratories HIBS User Facility and its application to the calibration of TXRF reference materials. We will compare HIBS and TXRF mapping capabilities and discuss the issues associated with the restrictions of some older TXRF sample stages. We will also discuss Motorola's cross-calibration of several TXRF systems using different elements as references.     

Elemental analysis of human amniotic fluid and placenta by total-reflection X-ray fluorescence and energy-dispersive X-ray fluorescence: child weight and maternal age dependence

This work is an attempt to evaluate the possible influence of the mother's age in trace element concentrations in human amniotic fluid and placenta and whether these concentrations are correlated to the weight of the newborn infants. Total-reflection X-ray fluorescence (TXRF) was used to analyze 16 amniotic fluid samples, and the placenta samples were analyzed by energy dispersive X-ray fluorescence (EDXRF). The whole samples were collected during delivery from healthy mothers and healthy infants and full-term pregnancies. According to the age of the mother, three different groups were considered: 20–25, 25–30 and 30–40 years old. Only two mothers were aged more than 35 years. The weight of the infants ranged from 2.56 to 4.05 kg and three groups were also considered: 2.5–3, 3–3.5 and 3.5–4 kg. The organic matrix of the amniotic fluid samples was removed by treatment with HNO₃ followed by oxygen plasma ashing. Yttrium was used as the internal standard for TXRF analysis. Placenta samples were lyophilized and analyzed by EDXRF without any chemical treatment. Very low levels of Ni and Sr were found in the amniotic fluid samples, and were independent of the age of the mother and weight of the child. Cr, Mn, Se and Pb were at the level of the detection limit. Zn, considered one of the key elements in neonatal health, was not significantly different in the samples analyzed; however, it was weakly related to birth weigh. The concentrations obtained ranged from 0.11 to 0.92 mg/l and 30 to 65 μg/g in amniotic fluid and placenta, respectively. The only two elements which seemed to be significantly correlated with mother's age and newborn weight were Ca and Fe for both types of sample: Ca levels were increased in heavier children and older mothers; however, Fe increased with increasing maternal age, but decreased for heavier babies. The same conclusions were obtained for placenta and amniotic fluid samples. Cu is closely associated with Fe in its function in the organism and has a similar behavior to this element, but not as pronounced.     

Determination of metal-cofactors in respiratory chain complexes by total-reflection X-ray fluorescence spectrometry (TXRF)

Total Reflection X-Ray Fluorescence Spectrometry (TXRF) offers many advantages for the detection of trace elements in enzymes as compared to other well known analytical techniques like flame-AAS or ICP-AES because of the significantly smaller amounts of sample required. Without any decomposition, elements like Fe, Ni, Cu, Zn, Mn and Mo could be determined with high accuracy, in spite of the large bio-organic matrix. Besides the metals also sulfur can be determined in protein samples. The two terminal oxidases, cytochrome c oxidase and quinol oxidase, isolated from the soil bacterium Paracoccus denitrificans, were transferred from their usual salt buffer into a solution of 100 mmol/L tris(hydroxymethyl)aminomethane (TRIS) acetate containing an appropriate detergent. By this procedure an improved signal/noise ratio is attained. The data for cytochrome c oxidase are in good agreement with values obtained by ICP-AES. Further results of quinol oxidase, which has different element ratios, also fit the expected values. The investigations lead to the conclusion that the method is well suited for the quantitative determination of metals in enzymes, and in particular their molar ratios, and requires only small amounts of the biological sample without any extensive pretreatment.     

Microanalysis of old violin varnishes by total-reflection X-ray fluorescence

Total reflection X-ray fluorescence was used to characterize elements (with Z>13) contained in varnishes applied by prominent violin makers during the last five centuries. Direct analyses of small flakes with masses <20 μg show a variety of elements. Some of these elements could be related to key elements of inorganic pigments and additives used to control some of the properties of a varnish. Higher amounts of Fe, As and Pb were found in old products, Mn, Co, Cu, Zn and Pb were used in more recent varnishes. © 1997 Elsevier Science B.V.     

Multi-element determination of dissolved heavy metal traces in sea water by total-reflection x-ray fluorescence spectrometry

Dissolved heavy metal traces in sea water are determined by a procedure based on total-reflection x-ray fluorescence spectrometry (t.x.r.f.). The trace elements are separated from the salt matrix by chelation with sodium dibenzyldithiocarbamate, selective chromatographic adsorption of the metal complexes onto a lipophilized silica-gel carrier, and subsequent elution of the metal chelates by a chloroform/methanol mixture. Aliquots of the eluate are then dispensed onto highly polished quartz sample carriers and evaporated to thin films for the t.x.r.f. measurements. The following elements can be determined: V, Mn, Fe, Co, Ni, Cu, Zn, Se, Mo, Cd, (Hg), Pb, and U. For 200-ml samples and a measuring time of 1000 s, detection limits of 5–20 ng kg^?1 are achieved for most of these elements. The limits are slightly higher for iron, zinc and mercury because of fluctuations in the blank values. Systematic investigations of the yield in the separation and enrichment step are described, and the procedure is characterized with regard to blanks, detection limits, precision and accuracy. The accuracy was checked with the aid of the sea-water reference material NASS-1. Some applications to Baltic sea water and open ocean waters are reported and discussed in terms of their information content.     

Size-fractionated sampling and chemical analysis by total-reflection X-ray fluorescence spectrometry of PMx in ambient air and emissions

PM 10 and PM 2.5 (PMx) have been recently introduced as new air quality standards in the EU (Council Directive 1999/30/EC) for particulate matter. Different estimates and measurements showed that the limit values for PM 10 will be exceeded at different locations in Europe, and thus measures will have to be taken to reduce PMx mass concentrations. Source apportionment has to be carried out, demanding comparable methods for ambient air and emission sampling and chemical analysis. Therefore, a special ambient-air sampler and a specially designed emission sampler have been developed. Total-reflection X-ray fluorescence analysis (TXRF) was used for multi-element analyses as a fast method with low detection limits. For ambient air measurements, a sampling unit was built, impacting particle size classes 10–2.5 μm and 2.5–1.0 μm directly onto TXRF sample carriers. An electrostatic precipitator (ESP) was used as back-up filter to also collect particles <1 μm directly onto the TXRF sample carriers. Air quality is affected by natural and anthropogenic sources, and the emissions of particles <10 μm and <2.5 μm, respectively, have to be determined to quantify their contributions to the so-called coarse (10–2.5 μm) and fine (<2.5 μm) particle modes in ambient air. For this, an in-stack particle sampling system was developed, according to the new ambient air quality standards and in view of subsequent analysis by TXRF. These newly developed samplers, in combination with TXRF analyses, were employed in field campaigns to prove the feasibility and capabilities of the approach. Ambient air data show the quantification of a wide spectrum of elements. From those concentrations, PMx ratios were calculated as an indicator for different sources of elements. Results useful for source apportionment are also the elemental day/night ratios calculated to determine local contributions to PMx mass concentrations. With regard to the emission measurements, results of mass and elemental concentrations obtained in two different processes (steel industry) show that the new PM 10/PM 2.5 cascade impactor and measurements with TXRF give characteristic fingerprints for different sources. Size-fractionated ambient air and emission sampling, together with multi-element analysis, prove to be a useful approach to derive information for source–receptor modeling, a method necessary to set up effective abatement strategies to reduce PMx mass concentrations.     

X射线荧光光谱法测定锡矿石中锡

本文采用向样品中加入硼酸来降低基体效应,加入氧化镧来稳定样品总质量吸收系数,建立固体粉末压片制样-X射线荧光光谱法测定锡矿石中锡含量的方法。通过将标准物质按一定比例混合配制和选取部分自制标样来补充标准物质样品,以解决锡矿石标准物质样品缺乏的问题。实验优化了稀释比,确定了以最佳稀释比为m（矿物质样品）:m（硼酸）：m（氧化镧）=1.0:2.0:0.5。在最优的实验条件下,Sn的荧光强度（kcps）与Sn浓度CSn呈良好的线性关系,R2=0.9989。方法中锡元素的最低检出限为0.005 %,测定范围在0.015 %-4.47 %之间。样品的混合均匀性实验表明各元素测定结果的相对标准偏差（RSD,n=6）在1.0 %-2.64 %之间。对3个不同含量段的物质进行测定来验证方法的准确度和精密度,准确度分别为0.0082-0.0367,均小于0.04,精密度分别为0.39 %-1.18 %,均小于8.0 %,准确度和精密度均符合地质样品分析规范要求。测定值均在误差范围内,各组分测定结果的相对标准偏差（RSD,n=11）在1.20 %以下。粉末压片-X射线荧光光谱法测定锡矿石中锡含量具有分析范围广、分析时间短、重现性好、精度高且操作简单等特点。能应用于地质、环境、材料等领域。     

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.     

Sapphire sample carriers for silicon determination by total-reflection X-ray fluorescence analysis

Sapphire is presented as a new sample carrier material for total-reflection X-ray fluorescence spectrometry (TXRF). A comparison with conventional sample carrier materials such as quartz glass, Perspex®, glassy carbon and boron nitride demonstrates that sapphire has all the physical and chemical properties required for TXRF micro and trace analysis. Moreover, sapphire sample carriers allow the determination of silicon in many matrices in a comparatively simple way. Especially for airborne particulate matter, acid digestion can be avoided by cool-plasma ashing of suitable filter materials directly on the sample carrier. This technique has been successfully applied to environmental samples.     

Study of interaction of iron and lead during their uptake process in wheat roots by total-reflection X-ray fluorescence spectrometry

Microwave assisted acidic digestion and total-reflection X-ray fluorescence spectrometry (TXRF) was used for the determination of lead and iron in wheat roots cultured in CaSO₄ solution, and treated with Pb(NO₃)₂ and Fe(III)–citrate or Fe(III)–EDTA under controlled conditions, respectively. It was established that lead has a stimulation effect on the iron uptake in the presence of Fe(III)–citrate. The lead uptake, however, is hardly influenced by iron independently from the complex forming agents applied. To check the stability of the accumulated iron and lead constituents, some of the roots were washed with various solutions and the removable iron and lead were also measured by TXRF. These experiments indicate that the presence of lead results in higher stability of iron constituents in the root; however, iron does not have any effect on the lead constituents, the stabilities of which increase in the order Pb–citrate<Pb–(cell wall)<Pb–EDTA. © 1997 Elsevier Science B.V.     

Determination of mercury by total-reflection X-ray fluorescence using amalgamation with gold

Analysis by total-reflection X-ray fluorescence (TXRF) is unsuitable for determining mercury concentrations because the usual sample preparation produces evaporation and loss of this element as a consequence of its high vapour pressure and low boiling point.A method that has been developed to achieve this determination involves forming an amalgam while a thin layer of silver (obtained by sputtering or evaporation) is in contact with an ionic solution of Hg; subsequently, a traditional TXRF analysis is performed. This was the first method reported in the literature to apply the TXRF technique for reliably determining mercury concentrations with high sensitivity.This work shows how a similar procedure may be employed to measure mercury concentrations. This second method involves forming an amalgam of gold using microlitre quantities of the solution to be analysed. As gold is a highly malleable material, it allows the production of very thin films, the weight of which is a few orders of magnitude higher than the mass of mercury present in the amalgam. The determination is performed in the usual way using the TXRF technique. The sensitivity of this method (≈ 5 ppm) is inferior to that of the former method, and data processing is quite difficult because the peaks for mercury and gold overlap, but the experiment is simple to execute and improved sensitivity is expected to be attained by forming the amalgam with larger volumes of sample and with a more responsive data processing scheme.     

Analysis of archaeological ceramics by total-reflection X-ray fluorescence: Quantitative approaches

This paper reports the quantitative methodologies developed for the compositional characterization of archaeological ceramics by total-reflection X-ray fluorescence at two levels. A first quantitative level which comprises an acid leaching procedure, and a second selective level, which seeks to increase the number of detectable elements by eliminating the iron present in the acid leaching procedure. Total-reflection X-ray fluorescence spectrometry has been compared, at a quantitative level, with Instrumental Neutron Activation Analysis in order to test its applicability to the study of this kind of materials. The combination of a solid chemical homogenization procedure previously reported with the quantitative methodologies here presented allows the total-reflection X-ray fluorescence to analyze 29 elements with acceptable analytical recoveries and accuracies.     

The use of Si carriers for aerosol particle collection and subsequent elemental analysis by total-reflection X-ray fluorescence spectrometry

The adoption of polished Si carriers was studied for the sensitive elemental analysis of aerosol particles using total-reflection X-ray fluorescence (TXRF) spectrometry. The surface roughness of the Si carrier measured by atomic force microscopy was found to be smaller than those of glassy carbon and quartz glass carriers, which are commonly used for TXRF analysis. The detection limits of elements for the Si carrier were superior to those for the glassy carbon and the quartz glass carriers, presumably due to its smaller surface roughness. For example, the detection limit of Sr for the Si carrier was 9 pg, which was 100 times and 3 times lower than those for the glassy carbon and the quartz glass carriers, respectively. The Si carriers could be successfully applied to the direct aerosol particle collection by impaction and the subsequent elemental analysis by TXRF. From the results of the elemental analysis of aerosol particles, the variations in the concentrations of K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn Sr and Pb with time could be clarified.