Nigerian coal analysis by PIXE and RBS techniques

PIXE and RBS techniques were employed for the measurement of the concentrations of the major, minor and trace elements in Nigerian coal samples from a major deposit. The samples were irradiated with 2.55 MeV protons from the 3 MeV tandem accelerator (NEC 3 UDH) in Lund. The PIXE results are reported and compared with an earlier work on Nigerian coal using FNAA and INAA analytical techniques while the RBS results are compared with ASTM previous results. The results show that Nigerian coals have a low (0.82–0.99)% sulfur content. This is quite important for pollution control reasons.     

Bronze analysis by k0-NAA and PIXE

Five copper alloys were prepared with modern powder metallurgical processes in the frame of the European project Improvement of Means of Measurement on Archaeological Copper-Alloys for Characterisation and Conservation (IMMACO) and certified for As, Pb, Sn and Zn mass fractions. Similar in their composition to archaeological bronze alloys, these Certified Reference Materials (CRMs) are to be used for calibration of XRF instruments for characterization of archaeological samples either in the laboratory or in the field. This paper presents and compares the successful contribution of our non-destructive analytical methods (k ₀-NAA and PIXE) to the IMMACO project and to the certification of the five reference materials.     

Trace analysis of lithium metal by PIXE

A rapid method is described for simultaneous trace determination of metallic impurities in lithium metal by Particle Induced X-ray Emission (PIXE) technique. The impurities were preconcentrated by ion-exchange separation using a weak cation exchanger, Bio Rex-70 and analyzed by 2.34 MeV protons. The reliability of the method was tested by analyzing synthetic samples having several metallic impurities at 1–5 ppm range.     

Calibration of Micromatter Co. standards used for the calibration of PIXE analysis systems

The evaluation of the accuracy of thin elemental standards produced by Micromatter Co., which are widely used for the calibration of the detection sensitivity of PIXE analysis systems, is presented in terms of Rutherford scattering measurements of the thickness of 68 standards covering a range of 59 different elements.     

PIXE analysis of allanites

Allanites from Telixtlahuaca (Oaxaca, Mexico) were analyzed using the PIXE technique. The concentrations of 12 elements, mainly rare earths, were determined.     

Prompt analysis of rare earths by high-energy PIXE

Thin targets of rare earth fluorides were bombarded with 66 and 85 MeV protons. Measured cross sections for X-ray production agreed with PWBA calculations. Satellite X-rays from nuclear reactions were obtained for both (Z-1) and (Z+1) products from the bombardment of element Z. Interference-free sensitivities were of the order of tens of nanograms under bombardment with 1 mC of integrated charge. The technique was applied for the analysis of geological ores and standards.     

XRF induced by PIXE: Comparison with PIXE

Two different modes of sample excitation have been used for elemental analysis of thin standard reference materials and of chemical standards with known composition. PIXE /2.5 MeV protons/ and XRF induced by PIXE, will be called XRF-PIXE /2.5 MeV protons on Mo primary target/. The same samples were alternatively exposed to protons and X-ray beams. The sensitivities under standard running conditions are determined for both an XRF-PIXE and a PIXE analysis system. It is shown that the sensitivity of the PIXE spectrometer depends strongly on the sample matrix, whereas the XRF-PIXE sensitivity is rather constant with respect to different kinds of samples. In addition, the advantages of one mode of excitation on the other are discussed. It is shown that XRF-PIXE can be a useful complement to PIXE analysis.     

Using additional standards for increasing the accuracy of quantitative chromatographic analysis

Uncontrolled partial losses at the step of sample injection into a gas chromatographic column increase errors of determination by the external standard, absolute calibration, and standard addition methods. Modified method is proposed for quantitative analysis; it includes the introduction of additional standards into test samples and calculations by the ratio between the areas of chromatographic peaks and peaks of standards rather than the absolute areas of chromatographic peaks. The calculation equations are presented for modified methods of quantitative analysis using additional standards, including those for estimating random errors of determination. The relative standard deviations of peak areas were shown to be 6–38-fold lower than the analogous statistical characteristics of absolute areas. This ensures a high accuracy of quantitative determinations even under the conditions of low reproducibility of sample dosing. Solvents contained in the analyzed samples can be used as additional standards. This version can be recommended as a routine method of data representation and processing.     

Analysis of geological standards with PIXE and PIGE technioues applications to volcanic rocks

Geological standards are analyzed using PIXE and PIGE techniques. The concentrations of up to 26 elements are determined and compared with those obtained by other methods. PIXE and PIGE techniques are also applied to different volcanic rock samples. Their sensitivity, accuracy, and speed of data collection and reduction, are of great interest in the study of volcanic phenomena.     

XRF and PIXE analysis of metallic glasses

Radionuclide X-ray fluorescence (XRF) and particle induced X-ray emission (PIXE) methods have been used for a rapid and nondestructive analysis of metallic glasses. The methods are compared in accuracy and precision with the atomic absorption method. Some results of analyses of Fe_xNi₈₀-_xB₂₀ materials are briefly reviewed. The distribution of elements along the width as well as length and a qualitative analysis of the composition of material surfaces are considered.     

Characterization of colour pigments in pre-Columbian Chilean potteries by PIXE elemental analysis

Ancient ceremonial potteries belonging to pre-Columbian cultures in Chile, South America, are decorated with three different colours, red, white and black. Samples of these colours have been analyzed with induced X-ray fluorescence by a 6.6 MeV proton beam. The analyses show clearly distinct patterns for each pigment and also denote differences between the same colour in two cultures. Eight elements, from aluminium to copper were detected.Under partial support from the Departamento Técnico de Investigación de la Universidad de Chile, Grant 2438-8833.     

Non-destructive analysis of early glass unearthed in south China by external-beam PIXE

External-beam PIXE was used for the non-destructive analysis of early glasses unearthed from the tombs of Warring States (475–221BC) and Han Dynasty (BC 206–AD 220) in south China. It was found that these glasses were basically attributed to PbO—BaO—SiO₂ system and K₂O—SiO₂ system. The results from the cluster analysis showed that some glasses had exactly the same recipe. The source of the K₂O flux and the correlation between PbO and BaO are discussed. Some archeological information is revealed.This revised version was published online in November 2005 with corrections to the Cover Date.     

Elemental analysis of Pterocarpus Santalinus by PIXE and ICP-MS: chemometric approach

Journal of Radioanalytical and Nuclear Chemistry - A biomonitoring study of air pollution using lichen Flavoparmelia caperata (L.) Hale was conducted at indoor and outdoor environments of primary...     

Precision and accuracy of laser ablation-ICP-MS analysis of rare earth elements with external calibration

Solid sample introduction into an ICP-MS by laser ablation is an effective method for the total analysis of rare earth elements (REEs) in soils because no digestion is needed. A problem of the method, however, is the difference of the ablated mass for each laser shot. Therefore, internal standard for the compensation of signal instability, sample preparation, and the calibration method have to be carefully chosen.The analyzed sample was a certified standard provided by IAEA (SOIL-7). The sample was mixed with an internal standard solution and polyethylene (PE), dried, homogenized in a ball-mixer/mill, and pressed to a pellet. For the calibration 5 external standards with increasing REEs concentrations (0.4–20 g/g) as well as a blank were prepared in the same way.The analysis of the pellets was performed on a VG PlasmaQuad II + with a LaserLab unit. The laser ablation-cell was modified to improve the sample particle transportation characteristics and to allow a quicker sample-exchange. The pellets were ablated from six different spots for 60 s each with a laser-repetition rate of 4 Hz.The correlation coefficients of the calibration curves based on 5 standards, were better than 0.995. The concentrations c_A of the 15 REEs in the soil sample were determined with an average relative confidence interval 100(CI)/c_A of 6.95%, as a figure for the precision. This good precision have been obtained with a new laser ablation cell, which will be described in detail.With 2 exceptions (Ce and La) the measured concentrations were within the confidence intervals (CI) of the certified values. Therefore, with respect to accuracy and precision, the presented method offers a convenient way to analyze homogeneous and powdered soil samples for REE's without digestion. Since a good calibration for the REE determination may be obtained, the laser sampling variance (within the sample) is less significant than the analytical variance. Automation of the method is possible by construction of an autosampler based on the modified laser cell.Presented in part at the 1993 European Winter Conference on Plasma Spectrochemistry, Granada, Spain     

Determination of major and trace elements in bones by simultaneous PIXE/PIGE analysis

The training process and training programs in both commercial nuclear plants and Department of Energy (DOE) nuclear facilities have improved significantly in the years following the Three-Mile Island (TMI) accident. This article describes some of these changes, including the reasons behind the change, the affected population, the training accreditation process and performance-based training, and the benefits of the changes.     

High accuracy determination of235U in nondestructive assay standards by gamma spectrometry

High precision gamma spectrometry measurements have been made on five sets of uranium isotope abundance reference materials for nondestructive assay (NDA). These sets are intended for international safeguards use as primary reference materials for the determination of the²³⁵U abundance in homogeneous uranium bulk material by gamma spectrometry. The measurements were made to determine the count rate uniformity of the²³⁵U 185.7 keV gamma-ray as well as the²³⁵U isotope abundance for each sample. Since the samples were packaged such that the U₃O₈ is infinitely thick for the 185.7 keV gamma-ray, the measured count rate was not dependent on the material density. In addition, the activity observed by the detector was collimated to simulate calibration conditions used to measure bulk material in the field. The sample-to-sample variations observed within the 5 sets of samples ranged between 0.005–0.11% (1s) with standard deviations of the mean ranging from 0.01–0.02%. This observed variation appears to be due predominantly to counting statistics and not to material inhomogeneity and/or packaging. The results of this study indicate that accuracy of²³⁵U determinations via gamma spectrometry, in the range of few hundredths of a percent (2), is achievable. The main requirement for achieving this level of accuracy is a set of standards whose²³⁵U isotope abundances are known to within 0.01% (2).     

Precision at the low picogram level in the analysis of derivatized iodothyronine standards by capillary gas chromatography with electron-capture detection

Previously an acceptable precision (coefficient of variation less than 10%) could be obtained only part of the time for the peak areas of derivatized iodothyronine standards, even relative to that of a structurally close internal standard, 3,4-diiodo-3′,5′-dibromothyronine, when these compounds were analyzed at the low picogram level by capillary gas chromatography with electron-capture detection. This problem has now been ovecome, primarily by introducing a new design, material and conditioning of a direct vapor-injector insert. An extensive analysis under practical operating conditions of derivatized 3,5-di-, 3,5,3′-tri and 3,5,3′,5′-tetraiodothyronine at the 5-10-pg level, involving several changes in the injection equipment and several days of injections, now gives within-day coefficients of variation ranging from 2.7 to 7.7%, 1.5 to 5.3% and 1.8 to 5.2%, respectively, for the relative peak areas of these compounds.     

Precision, accuracy and referencing of isotope ratios determined by nuclear magnetic resonance

Summary The precision and accuracy of site-specific and average hydrogen isotope ratios determined by NMR are checked according to the ISO norms. The consistency of the results is investigated by comparison with the values of the mean isotope ratios measured by mass spectrometry. Several kinds of molecular species from different natural origins have been studied: water, ethanol, anethol, vanillin. A very good agreement between MS and NMR results is found for water. The limitations and advantages of NMR for the determination of average deuterium contents of organic molecules are discussed. A satisfactory precision of the NMR measurements can usually be reached, however systematic deviations of a few ppm between MS and NMR results may occur. By using either MS or NMR mean isotope ratios, site-specific parameters can be obtained by SNIF-NMR with an accuracy which is strongly dependent on the structure of the molecular species. The role and the importance of the reference materials in quantitative isotope determinations are stressed.

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Genauigkeit, Richtigkeit und Verifizierung von Isotopenverhältnissen mit Hilfe der NMR-Spektroskopie

     

Standardless PIXE analysis of thick biomineral structures

The particle-induced X-ray emission (PIXE) of thick biomineral targets provides pertinent surface analysis, but if good reference materials are missing then complementary approaches are required to handle the matrix effects. This is illustrated by our results from qualitative and semiquantitative analysis of biomaterials and calcified tissues in which PIXE usually detected up to 20 elements with Z > 14 per sample, many at trace levels. Relative concentrations allow the classification of dental composites according to the mean Z and by multivariate statistics. In femur bones from streptozotocin-induced diabetic rats, trace element changes showed high individual variability but correlated to each other, and multivariate statistics improved discrimination of abnormal pathology. Changes on the in vitro demineralization of dental enamel suggested that a dissolution of Ca compounds in the outermost layer results in the uncovering of deeper layers containing higher trace element levels. Thus, in spite of significant limitations, standardless PIXE analysis of thick biomineral samples together with proper additional procedures can provide relevant information in biomedical research.Abbreviations AAS Atomic absorption spectrometry - ERDA Elastic recoil detection analysis - ESR Electron spin resonance - FDA Factorial discriminant analysis - FTIR spectroscopy Fourier transform infra-red spectroscopy - HP Ge detector Hyperpure Ge detector - ICP-AES Inductively coupled plasma atomic emission spectrometry - NAA Neutron activation analysis - NRA Nuclear reaction analysis - PCA Principal component analysis - PIXE Particle-induced X-ray emission - PIGE Particle-induced -ray emission - RBS Rutherford backscattering spectroscopy - SRIXE Synchrotron radiation-induced X-ray emission     

Possible use of low voltage accelerators in PIXE analysis

A low energy (200 keV) accelerator routinely used as a neutron generator has been modified and a procedure established to extend the use to include proton induced X-ray emission (PIXE) analytical method. With these modifications, the generator has been used to measure the proton induced X-ray emission cross sections for twenty-eight elements ranging from aluminium to lead at 160 keV bombarding energy. Using these cross sections, the minimum detection limits for trace element determination in a rock matrix of average atomic number 13 have been evaluated.