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.

     

Rapid qualitative determination of main components in archeological samples by radioisotope-excited X-ray fluorescence analysis

Archeological specimen were examined by the radioisotope-excited X-ray method to determine their chemical composition. Individual K and L X-rays of Fe, Ni, Cu, Zn, Pb, Mo, Ag, In, Sn, Sb, and Ba were induced by using²⁴¹Am−I and²⁴¹Am−Tm source—target assemblies. A lithium drifted silicone diode coupled to a 400-channel analyzer was used for detection. No sample preparation was required and all the elements were measured simultaneously in 40 min counting time.     

Quantitative analysis by X-ray photoelectron spectroscopy without reference samples

A comparison between X-ray fluorescence analysis (XRFA) and X-ray photoelectron spectroscopy (XPS) indicates the applicability of these two methods as relative and absolute techniques. For XPS the absolute field of application should be preferred. An improvement of the Hirokawa-Ebel method (an absolute XPS analysis) is presented in this paper. It is shown that the knowledge of the inelastic mean free paths of the photoelectrons (IMFP) is no longer required, but the energy dependence of the IMFPs can be used as a basis. This guarantees simplicity and much more universal applicability.     

Radioanalytical methods for the non-destructive analysis of lunar samples

The elemental compositions of Apollo 11 and Apollo 12 lunar soil samples 10084,141 and 12070,83 and Apollo 12 rock fragment 12063,73 were determined by non-destructive radioanalytical methods. Main mineral fractions and glasses separated from these samples were analyzed as well. Instrumental neutron activation analysis (INAA) was used to determine Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Cs, Ba La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, Lu, Hf, Ta, W, Ir, Au, Th and U. A method of delayed neutron counting was used for the determination of uranium, and non-dispersive radioisotopic X-ray fluorescence analysis was applied to the determination of Ti, Fe, Sr, Y and Zr.     

Selenium determination in biological samples by X-ray emission spectroscopy

Determination of Se in blood serum by PIXE and XRF is presented. Two different sample preparation methods combined with two modes of sample excitation are compared. Both methods are shown to be suitable for Se determination in blood serum and in standard reference materials (horse kidney IAEA H-8 and bovine liver NBS 1577a).     

X-ray photoelectron spectroscopy for nondestructive analysis of buried interfaces

The possibility to use high energy X-ray photoelectron spectroscopy as a nondestructive method of in-depth chemical phase analysis of solids is demonstrated. Theoretical background and optimal experimental conditions of in-depth analysis are considered. Interfaces in 5 nm thick HfO₂ films synthesized by molecular layering and deposition of organometallic compounds from the gas phase were studied. It was shown that thickness of the layers in multilayer structures can be determined by measuring the intensity of photoelectron peaks.     

Quantitative surface analysis by X-ray photoelectron spectroscopy and X-ray excited auger electron spectroscopy

It is shown that X-ray excited KLL Auger electron spectra allow it to describe measured signal strengths similarly to X-ray photoelectron signals, thus offering valuable information on the quantitative surface composition of a solid sample. The principal equation and corresponding fundamental parameters are discussed. As a result Auger spectra of C, N, O, F, and Na can be easily used in a multiline approach for quantitative analysis. LMM and MNN spectra give rise to more problems, due to their more complicated structure, uncertainties with regard to the background and the influence of Coster-Kronig transitions. These problems are overcome by the use of empirical ratios of the strongest lines of 2p/LMM or 3d/MNN. Since these ratios are independent of sample composition, they allow it to transform the Auger signal into the corresponding photoelectron signal, provided that a standard sample has been measured. Thus a true additional information is obtained and moreover difficulties in cases of photoelectron spectra with overlapping lines from other chemical elements can be overcome.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Automated energy-dispersive X-ray fluorescence analysis of environmental samples

Summary A procedure is described for the routine automatic analysis of 20 elements in small environmental samples. Up to 50 samples a day can be processed. The instrument uses an energy dispersive X-ray spectrometer for the simultaneous detection of all elements during a 5–20 min measurement. Computer techniques are used for the subsequent data reduction of the X-ray spectra. The technique is applicable to air particulate matter filtered from the air, to suspended material in water which is filtered on a filter paper and to dissolved trace elements which are evaporated on filter paper or are collected on a thin ion-exchange loaded paper.

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Automatisierte energie-dispersive Röntgenfluorescenzanalyse von Umweltmaterial

Zusammenfassung Ein Verfahren zur automatischen Routinebestimmung von 20 Elementen in Umweltmaterial wird beschrieben. Bis zu 50 Proben je Tag können verarbeitet werden. Ein energie-dispersives Röntgenspektrometer wird zur simultanen Erfassung aller Elemente bei einer Messung von 5–20 min benutzt. Die nachfolgende Auswertung der Spektren wird mittels Computer durchgeführt. Das Verfahren findet Anwendung auf Schwebestaub oder in Wasser suspendierte Substanzen, die auf Filterpapier gesammelt wurden sowie auf gelöste Elementspuren, die auf Filterpapier getrocknet oder durch Ionenaustauschpapier angereichert wurden.

     

Electron probe X-ray microanalysis of archeological finds of the Baikal region

A procedure was developed for determining Fe, Ni, Sn, and Zn in copper by electron probe X-ray microanalysis. The dependence of the detection limits for analytes on excitation conditions was studied and the optimum conditions for measuring the analytical signal were found. It was shown that the precision of quantitative electron probe microanalysis depends on the homogeneity of the reference samples. Individual certified reference samples of copper alloys previously synthesized for spectrochemical and chemical analysis were applied to electron probe microanalysis and justified. Performance characteristics of the proposed procedure were evaluated. Examples of using the procedure for determining the composition of archeological finds from a burial place in the Baikal region are presented.     

Recognition of archeological materials underwater by laser induced breakdown spectroscopy

The detection of different materials immersed in seawater has been studied by means of Laser Induced Breakdown Spectroscopy. The plasma emission was produced by a Q-Switched Nd:YAG laser operated at 1064 nm in a dual pulse mode. Different classes of materials potentially found in the undersea archaeological parks, such as iron, copper-based alloys, precious alloys, marble and wood have been examined. Data acquisition and processing were optimized for better signal control and in order to improve the detection threshold. In all the examined cases but wood, qualitative analysis was successful and allowed for the material recognition. The spectral features necessary to clearly distinguish marble materials from calcareous rocks have been also established. It was found that these characteristic spectral intervals could be also used for the recognition of sedimentary layers deposited on the underwater findings. Quantitative chemical analysis was also performed on submerged bronze samples, after generating calibration curves with standards of similar matrix composition.     

Fast multidimensional localized parallel NMR spectroscopy for the analysis of samples

A parallel localized spectroscopy (PALSY) method is presented to speed up the acquisition of multidimensional NMR (nD) spectra. The sample is virtually divided into a discrete number of nonoverlapping slices that relax independently during consecutive scans of the experiment, affording a substantial reduction in the interscan relaxation delay and the total experiment time. PALSY was tested for the acquisition of three experiments 2D COSY, 2D DQF‐COSY and 2D TQF‐COSY in parallel, affording a time‐saving factor of 3–4. Some unique advantages are that the achievable resolution in any dimension is not compromised in any way: it uses conventional NMR data processing, it is not prone to generate spectral artifacts, and once calibrated, it can be used routinely with these and other combinations of NMR spectra. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of a micro-X-ray fluorescence system based on polycapillary X-ray optics for non-destructive analysis of archaeological objects

A new micro-X-ray fluorescence (micro-XRF) system based on rotating anode X-ray generator and polycapillary X-ray optics has been set up in XOL Lab, BNU, China, in order to be used for analysis of archaeological objects. The polycapillary X-ray optics used here can focus the primary X-ray beam down to tens of micrometers in diameter that allows for non-destructive and local analysis of sub-mm samples with minor/trace level sensitivity. The analytical characteristics and potential of this micro-XRF system in archaeological research are discussed. Some described uses of this instrument include studying Chinese ancient porcelain.     

Multielement analysis of environmental samples by total-reflection X-ray fluorescence spectrometry, neutron activation analysis and inductively coupled plasma optical emission spectroscopy

Summary In environmental research and protection trace elements have to be determined over a wide range of atomic number, down to very low concentrations, and in quite different matrices. This challenge requires the availability of complementary analytical methods characterized by a high detection power and few sources of systematic errors. Besides, the capacity of multielement detection is often desired since it facilitates the tackling of many problems in which numerous trace elements are of direct concern. Total reflection X-ray fluorescence, neutron activation analysis and inductively coupled plasma optical emission spectroscopy, in principle, fulfill these requirements quite well. However, each method has its domain, and the application to certain sample species may be less promising. Under this aspect, the paper summarizes some recent developments and investigations, including intercomparisons as far as possible. Various matrices are considered: rainwater and airborne particulates, soil samples, river sediments and suspended particulate matter, river water filtrates, ovean water, and organic matrices. Capabilities and limitations are discussed. Sample preparation techniques are described if they are new or essential for achieving the results given.

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Multielementanalyse von Umweltproben mit Totalreflexions-Röntgenfluorescenzspektrometrie, Neutronenaktivierungsanalyse und ICP-Emissionsspektroskopie

Zusammenfassung Umweltforschung und Umweltschutz erfordern die Bestimmung von Spurenelementen über einen weiten Bereich der Ordnungszahl, z. T. bis in den extremen Spurenbereich und in ganz unterschiedlichen Matrices. Die Erfüllung dieser Aufgabe setzt die Verfügbarkeit einander ergänzender analytischer Verfahren voraus, die durch eine hohe Nachweisstärke und geringe systematische Fehler gekennzeichnet sein müssen. Hinzu kommt, daß vielfach Multielement-Eigenschaften wünschenswert sind, da bei manchen Fragestellungen zahlreiche Elemente von Interesse sind. Die Totalreflexions-Röntgenfluorescenzanalyse, die Neutronenaktivierungsanalyse und die optische Emissionsspektroskopie mit induktiv angeregter Plasmafackel erfüllen grundsätzlich diese Forderungen in hohem Maße. Jedoch besitzt jede Methode ihre besonderen Stärken, und Anwendungen auf bestimmte Probenarten können weniger erfolgreich sein. Der vorliegende Beitrag faßt unter diesem Aspekt einige neuere Entwicklungen und Untersuchungen zusammen, wobei nach Möglichkeit Vergleiche der verschiedenen Verfahren angestellt werden. Dabei werden die folgenden Matrices behandelt: Niederschlag und luftgetragene Partikel, Bodenproben, Flußsedimente und Schwebstoffe, Flußwasserfiltrate, Ozeanwasser und einige organische Matrices. Die Einsatzmöglichkeiten und die Leistungsgrenzen werden diskutiert. Die Probenvorbereitungstechniken werden beschrieben, sofern sie neu sind oder eine wesentliche Voraussetzung für die Erzielung der angegebenen Ergebnisse darstellen.

     

Picoliter solution deposition for total reflection X-ray fluorescence analysis of semiconductor samples

A deposition system capable of delivering picoliter quantities of solution in programmable arrays was investigated as a method for sample preparation for total reflection X-ray fluorescence (TXRF) spectroscopy. Arrays of trace metals in solution were deposited on Si wafers. The array deposits provide a capability of depositing closely spaced (100 μm or less), typically 5–20 μm diameter droplets in an area that can be matched to the analysis spot of the TXRF detector. The dried depositions were physically characterized and the effect of deposition type and matrix on the TXRF signal was investigated.     

Monte Carlo and experimental efficiency calibration of gamma-spectrometers for non-destructive analysis of large volume samples of irregular shapes

A comparison of efficiency calibration of a HPGe gamma-ray spectrometer applied for non-destructive analysis of gamma-ray emitters in large volume samples of irregular shape is presented. The detector efficiency calibration was carried out during the analysis of cosmogenic radionuclides (⁶⁰Co, ⁵⁴Mn, ²²Na and ²⁶Al) in fragments of the Ko?ice meteorite. Fourteen meteorite fragments were available for the analysis with masses from 27 to 2,163 g. A reasonable agreement in the estimation of the HPGe detector efficiency was obtained using the Monte Carlo simulation GEANT 3 code, and the experimental calibration using radioactive standards mixed with iron–silica–copper powder housed in mock-ups of similar shapes as the original samples. The differences in the efficiency estimation obtained by both methods were within 10 %. It is recommended that the Monte Carlo simulation of the detector efficiency can be applied in routine analysis of gamma-ray emitters in large volume samples of regular or irregular shapes.     

Comparison of conventional and total reflection excitation geometry for fluorescence X-ray absorption spectroscopy on droplet samples

X-ray absorption fine structure (XAFS) experiments in fluorescence mode have been performed in total reflection excitation geometry and conventional 45°/45° excitation/detection geometry for comparison. The experimental results have shown that XAFS measurements are feasible under normal total reflection X-ray fluorescence (TXRF) conditions, i.e. on droplet samples, with excitation in grazing incidence and using a TXRF experimental chamber. The application of the total reflection excitation geometry for XAFS measurements increases the sensitivity compared to the conventional geometry leading to lower accessible concentration ranges. However, XAFS under total reflection excitation condition fails for highly concentrated samples because of the self-absorption effect.     

Precise non-destructive X-ray fluorescence method for uranium and thorium concentration measurements

A precise non-destructive radioisotope X-ray fluorescence method for uranium and thorium concentration measurements was developed. A beta-emitting⁹⁰Sr−⁹⁰Y source was used for excitation of characteristic X-ray lines. It is proved that the beta-excited X-ray fluorescence method (in spite of the significant bremsstrahlung intensity) has essential advantages for analysis of high concentrations of U and Th, characteristic for nuclear power cycle materials, because of the higher sensitivity of the method. (3% changes of the intensity per 1% change of the concentration.) Portable semiconductor or scintillation detectors and multichannel analysers are used for detection of analytical lines. The accuracy achieved by this method is 0.2–0.3% for 15 minutes measurement and 0.1 mCi activity of the source. This work was performed under contract with the International Atomic Energy Agency, Vienna.     

Quantitative laser-induced breakdown spectroscopy analysis of calcified tissue samples

We report on the application of laser-induced breakdown spectroscopy (LIBS) to the analysis of important minerals and the accumulation of potentially toxic elements in calcified tissue, to trace e.g. the influence of environmental exposure, and other medical or biological factors. This theme was exemplified for quantitative detection and mapping of Al, Pb and Sr in representative samples, including teeth (first teeth of infants, second teeth of children and teeth of adults) and bones (tibia and femur). In addition to identifying and quantifying major and trace elements in the tissues, one- and two-dimensional profiles and maps were generated. Such maps (a) provide time/concentration relations, (b) allow to follow mineralisation of the hydroxyapatite matrix and the migration of the elements within it and (c) enable to identify disease states, such as caries in teeth. In order to obtain quantitative calibration, reference samples in the form of pressed pellets with calcified tissue-equivalent material (majority compound of pellets is CaCO₃) were used whose physical properties closely resembled hydroxyapatite. Compounds of Al, Sr and Pb were added to the pellets, containing atomic concentrations in the range 100–10 000 ppm relative to the Ca content of the matrix. Analytical results based on this calibration against artificial samples for the trace elements under investigation agree with literature values, and with our atomic absorption spectroscopy (AAS) cross-validation measurements.