Lead determinations in human bone by particle induced X-ray emission (PIXE) and graphite furnace atomic absorption spectrometry (GFAAS)

Chronic lead (Pb) intoxication has been linked to Alzheimer's disease (AD). Lead, like many heavy elements, tends to accumulate in bone. PIXE is a powerful analytical tool which permits the determination of Pb at the g/g level without requiring sample digestion. GFAAS is one of the most sensitive methods for the determination of Pb and is capable of determining ng/g levels in solution. For bone analyses by GFAAS, sample dissolution and a matrix modifier are required. Rib bone samples were analyzed for Pb by PIXE and GFAAS. IAEA Animal Bone (H-5) was used as a secondary standard for Pb with both methods to ensure accuracy. The range of Pb concentrations in human rib bone was 1.4–11.5 g/g for the trabecular surface by PIXE, 1.3–45 g/g for the cortical surface by PIXE, and 1.54–11.75 g/g for whole bone by GFAAS. No significant difference (p>0.05) was found for AD versus control for either surface or for whole bone.     

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     

Trace elements in human fingernails: Measurement by proton-induced X-ray emission

The method of proton particle-induced X-ray emission (proton PIXE) has been employed to study the trace element composition of human fingernails. The samples were colleted from 51 subjects randomly selected from a working community of about 500 adults and they were analyzed by the thick-target external beam technique of the PIXE method. The samples were exposed to the proton beam as 1-mm thick pellets and irradiated with 2 MeV protons having 20 nA beam intensity. For 40 C irradiations, the concentration of fourteen elements, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Rb, Sr and Pb, were measured by comparison with a calibration obtained from the NBS orchard leaf standard (SRM 1571). Some anomalous cases have been revealed from this study and they are attributed to environmental factors. The frequency distributions of the elements are presented and the results compared with available data.This research received financial support from the International Atomic Energy Agency, Vienna, under the research contract RC/2536/RBl.     

Inductively-coupled plasma atomic emission spectroscopic determination of trace impurities in ZrO2-powder

Four independent procedures including one using slurry nebulization ICP-AES were developed for the trace analysis of ZrO₂ powders. They were evaluated with respect to detection limits, blank values, interferences, accuracy and precision. For the procedures I–III ZrO₂ powder was decomposed by fusion with a 10-fold excess of NH₄HSO₄ and subsequent dissolution of the melt in either water or, after evaporation of NH₄HSO₄, in diluted HNO₃. In procedure I the solution was directly analyzed by ICP-AES, which was optimized with the aid of a simplex algorithm. In procedure II Zr was separated by extraction from 6 mol/l HNO₃ with a 0.5 mol/l solution of 2-thenoyltrifluoroacetone (TTA) in xylene. More than 99.5% of the Zr was removed and more than 95% of the trace elements retained. In procedure III the matrix was separated by its precipitation as ZrOCl₂·8 H₂O from a (1:4) HCl-acetone medium. More than 98% of Zr were removed and more than 90% of the trace elements were retained. In procedure IV the ZrO₂ powder was dispersed by ultrasonic treatment in water acidified with HCl (pH 2) and the slurry was directly analyzed by ICP-AES using a Babington nebulizer. The optimization and the analytical features of this procedure will be described in a subsequent paper. In all procedures the calibration was performed by standard addition and matrix matching was not necessary. The detection limits varied from 0.3 g/g (Ca) to 10 g/g (Al). The standard deviations obtained were 1–10% depending on the element and its concentration in the sample. The results of the procedures for 6 commercially available fine ZrO₂ powders were found to agree for Al, Ca, Fe, Mg, Na, Ti and Y. A good agreement between the results of the procedures using matrix separation was also observed for Cu, Mn, V, but the concentrations of these elements found by methods without matrix separation were considerably higher. Except for Ca and Mg the blank values encountered were below the detection limits.On leave from Department of Analytical Chemistry, Technical University, PL-00-664 Warsaw, Poland     

Combined application of INAA and PIXE for studying the regional aerosol composition in Southern Africa

As part of the SAFARI-92 biomass buming experiment, aerosol collections were carried out with several size-fractionating sampling devices at a number of sites in Southern Africa. One of the samplers used at all ground-based sites was a stacked filter unit (SFU). The SFU samples were analyzed by both INAA and PIXE analysis. The present paper gives an intercomparison of the analytical results obtained in order to assess the accuracy and to check the quality assurance of the analytical procedures. Twenty-one common elements were determined by both INAA and PIXE. Concentrations of 13 elements (i.e., Na, Mg, Al, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Zn and Br) were generally measured with sufficient precision in both techniques for performing the intercomparison. The INAA and PIXE data were compared in terms of PIXE/INAA concentration ratios on a sample by sample basis for the coarse and fine size fraction separately. the atmospheric concentrations for K, Mn and Fe agreed within 5–10%, the agreement between the data for the other common elements was typically better than 15%. Possible explanations for lower than 1.0 ratios for Cl, Br and Na are presented. The common elements were classified into groups according to their detectability and sensitivity in each technique.     

Status report: preparing an ambient aerosol filter reference material for elemental analysis

Summary For the elemental analysis of aerosol filter samples by X-ray techniques there is a lack of adequate reference materials (RM). No genuine aerosol matrix is available, which has been collected on membrane filters from ambient aerosol and can be distributed in the same physical form. It is possible to collect high-volume ambient aerosol samples, with a uniformity of 5% to 15%, in the elemental deposit ranges of 10 ng/cm² to g/cm² within probed spots of only 4 mm diameter on suitable filter materials. An aerosol sampling campaign is being organized, aiming at the collection of large enough filter batches of aerosols of different origin, suitable for characterization by different analytical methods and compatible with X-ray fluorescence analysis (XRF). To a large extent, the production control - especially for the homogeneity of the elemental mass deposits - will be performed by particle-induced X-ray emission (PIXE) analysis on residual material without consuming any part of the candidate RM stock.Working under contract CBNM/ST/91-147     

Determination of urinary bromine by pixe

The method of thin film PIXE was applied to the analysis of a total of 117 urine specimens from urinary stone sufferers and controls. The overall range of Br levels was between 2 and 18 g cm^–3. Mean values obtained over a period of three days ranged from 6.8 to 9.2 g cm^–3. No significant differences between the Br distributions in the two groups over the collection period were observed.     

Sample preparation of archaeological materials for PIXE analysis

A method to prepare thin samples of archeological materials such as potteries and bones for PIXE analysis is presented. In this method fine powder of the matter under analysis is suspended and deposited on polycarbonate filters. The process takes place in a chamber where clean air and the powder are mixed and forced to pass through the filter. Thin samples with typical mass density of about 50 g cm^–2 are obtained. The uniformity of the mass deposit has been optically tested with a He–Ne laser showing fluctuations of the order of one percent. Samples of clay standards from NIST were prepared with this method and analyzed by PIXE. The agreement between our results and NIST values is very good, with linear correlation factors close to unity. The method was applied to study the elemental composition of clay from different fragments of a Chilean pre-Hispanic pottery piece. These results are very consistent showing that the analysis of samples from a small fragment can represent the whole piece.Work supported in part by FONDECYT Grant 1052-92.     

Elemental analysis of the frontal lobe of “normal” brain tissue and that affected by Alzheimer's disease

Normal brain tissue and brain tissue affected by Alzheimer's disease has been taken from the frontal lobe of both hemispheres and their elemental compositions in terms of major, minor and trace elements compared. Brain samples were obtained from the MRC Alzheimer's Disease Brain Bank, London. 25 samples were taken from 18 individuals (5 males and 13 females) of mean age 79.9±7.3 years with pathologically confirmed Alzheimer'sdisease and 26 samples from 15 individuals (8 males and 7 females) of mean age 71.8±13.0 years with no pathological signs of Alzheimer's disease (normals). The elemental concentration of the samples were determined by the techniques of Rutherford backscattering (RBS) analysis, particle induced X-ray emission (PIXE) analysis and instrumental neutron activation analysis (INAA). Na, Mg, Al, Cl, K, Sc, Fe, Zn, Se, Br, Rb and Cs were detected by INAA and significant differences in concentrations were found between concentrations in normal and Alzheimer tissue for the elements. Na, Cl, K, Se, Br and Rb, P, S, Cl, K, Ca, Fe, Zn and Cd were detected by PIXE analysis and significant differences found for the elements P, S, Cl, K and Ca.     

Multi-element determination of trace elements in whole blood and blood serum by TXRF

Summary The suitability of total-reflection X-ray fluorescence analysis (TXRF) for multi-element determination in whole blood and human serum has been investigated. In combination with microwave digestion with nitric acid the elements P, S, K, Ca, Fe, Cu, Zn, Se, Rb, Sr, and Pb were determined in samples from several patients. The detection limits for heavy metal traces are in the range of 0.02 –0.08 g/ml, the precision is in the range of 2 –10%. The elements Mn, Ni and Pb could additionally be determined after iron-(only necessary for whole blood) and salt-matrix separation. In this way the detection limits could be improved by more than one order of magnitude (0.002 g/ ml). The accuracy of the results and the reliability of the analytical procedures are checked with the help of several certified reference materials. In general the accuracy is in the range of 2–15%.

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Multielement-Bestimmung von Spurenelementen in Gesamtblut und Blutserum durch TXRF

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Dedicated in gratitude to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Recent developments in chemical characterization with MeV ion beams

A multitude of ion-atom interactions are induced with projectiles of E0.1 MeV/nucleon. Analytical techniques derived from these include particle induced X-ray emission (PIXE), charged particle activation analysis (CPAA), prompt nuclear reactions (PNR), and Rutherford backscattering spectrometry (RBS). Among their features are broad elemental coverage (PIXE), subnanogram sensitivity (PIXE, CPAA), isotopic specificity (CPAA, PNR), and depth resolution (RBS, PNR). A limiting requirement with each technique is the need for high intensity ion beams. Novel approaches seek now to obtain analytical information with very small numbers of bombarding ions. Sample integrity is then maintained; moreover, they can be delivered in a microbeam (diameter 5 mm). A phenomenon which under these conditions provides useful analytical information is the particle induced desorption of molecular fragments. Thus, microscopic chemical analysis can be achieved with a small number (<10,000) of heavy fast projectiles and identification of the species desorbed from the sample surface via time-of-flight mass spectrometry. Experimental work with 84 MeV kr ions indicates the following: (a) high desorption yields can be obtained (>50%); (b) mass spectrometry on microspots (diameter of a few m) is feasible; (c) < 10⁶ atoms can be detected. Further capabilities of ion beams for minute, detailed, and comprehensive chemical characterization remain to be explored.     

Proton induced X-ray emission (PIXE) analysis on thick samples exemplified on the rare earth elements

Summary A semiempirical procedure is developed for the calculation of the signal intensity for thick sample PIXE experiments. The calculated X-ray intensity emerged out of a thick sample is factorized into the overall produced intensity within a thick sample and an effective transmission factor for the X-ray self-absorption.The accuracy of this procedure is limited by the reliability of the experimental input parameters to about ±25%.We find as an important result of this study: The signal intensity is calculated as a function of the various experimental parameters, i.e. proton energy and sample composition including interelement- and matrix effects. This function is presented as a closed equation, which can be applied very easily, i.e. without large scale computers, to calculate the sample elemental concentration. The mass absorption coefficient of the sample most strongly influences the effective transmission term.Enhancement corrections are calculated for additional interfering rare earth elements j. No significant interelement-effects appear at concentrations c _j 2 weight%, where analysis by PIXE may be interesting. The calculated results agree well with experimental data for the rare earth elements in different matrices.Dedicated to Karl Gleu on the occasion of his 80th birthday     

Study of trace elements in milk by nuclear analytical techniques

This work is part of a project with the IAEA, in a coordinated program on Trace Elements in Human and Bio-Environmental Systems to evaluate their nutritional requirements, interrelations and the role of trace elements in health, metabolism, etc. Cow's milk being regarded as one of the most important and nutritious foodstuffs consumed by people. Hence as a first step, an elemental analysis for milk was carried out for this purpose; a few samples of pasteurized milk and local sample were investigated for essential and toxic trace elements. The secondary aim of this project was the assessment of various analytical techniques involved. However, in the present work, the methods involved were AAS, PIXE and NAA. The latter method was applied both instrumentally and radiochemically. Although the results pertaining to the various methods employed are not in good agreement. there is, however, some justification to clarify this internal inconsistency. The precision of NAA and AAS allows a greater degree of acceptance. Although PIXE is very fast and rather routine, the technique for trace element analysis needs certain adaptations and development.     

Interlaboratory simultaneous multielement analysis of aerosol samples from Šumava mountains

The samples of the solid aerosol were taken in umava mountains (SFR/FRG frontier) to be analyzed by PIXE or XRF methods in the frame work of air pollution import investigation. To evaluate differences in the results and to minimize discontinuities in the time series, some analyses of the same samples were done by both methods. The peak areas of Al, Si, S, K, Ca, Ti, Cr, Mn, Fe, Cu and Zn were compared to establish the degree of correlation for separate elements. On the basis of the comparison, the multiplicative factors were determined to estimate the XRF peak areas from the PIXE ones. Relative element concentrations and other data were derived from both determined and estimated peak areas and taken into account in the preliminary stage of research.     

An external helium flushed milli-beam for combined PIXE and PIGE analysis

A helium flushed external beam PIXE/PIGE facility for nondestructive multielemental analysis has been developed and tested. By using proton energies E_p4.1 MeV and simultaneous detection of X- and gamma-rays, nearly complete analysis of all elements is achieved with nondestructively low ion current of I_p1 nA (except H, He, C, O and Ne are detected in a single measurement with sensitivities from the ppm level to about one percent). For most of the elements there are at least two channels of identification, which is a special advantage in analyzing unfavourable matrices, where the radiations of certain elements may interfere with each other.     

Determination of impurities in silicon carbide powders

Summary The analysis of SiC powders used for the production of high-performance ceramics was investigated by combined procedures as well as by a direct technique including atomic spectrometric detection. For the combined chemical procedure, SiC powders (0.25 g) were completely dissolved in a mixture of HNO₃, HF and fuming H₂SO₄ in an autoclave at 240°C within 8 to 20 h. In the final 0.5% w/v solution 13 elements were determined by electrothermal atomic absorption spectrometry (ETAAS) and by inductively coupled plasma atomic emission spectrometry (ICP-AES). With acid decomposition the detection limits for Ca, Cd, Cr, Cu, Mg, Mn and Zn were found to be in the range of 0.1–1 g/g; those for Al, B, Fe, Ni, Ti and V are at the 1–5 g/g level. With a Babingtontype nebulizer 1% slurries of SiC can be directly analyzed by ICP-AES. Calibration was performed by standard addition of aqueous solutions of the elements to be determined and the detection limits are close to those of ETAAS subsequent to pressure decomposition. The required analysis time was reduced from approx. 24 h to 30 min. First results for Ca, Cr, Cu, Mg, Mn, Ti and V as well as the needs to overcome systematic errors of this method, e.g. for Fe, are communicated.Part of this paper was presented at XI. International Symposium of Microtechniques, Wiesbaden, FRG, Aug. 28th–Sept. 1st 1989     

Performance of a nuclear microprobe to study giant marine aerosol particles

The scanning nuclear microprobe analytical facility of the IRMM was used to determine with PIXE major, minor and trace elements in individual giant marine aerosol particles, collected above the North Sea (particle size > 5 m Ø). The instrumentation is briefly described, and the experimental parameters chosen for these analyses are discussed. Elements with atomic numbers Z > 15 could be determined. Detection limits observed under the prevailing experimental conditions reached down to 50 fg in the case of Ti, V or Cr, corresponding to a mass content of 10 g/g in particles of 15 m size. Quantitative evaluation of the acquired spectra revealed basically three aerosol types in these samples: sea salt particles, sea salt combined with high contents of S, K and Ca, and particles rich in heavier elements (Ti, Cr, Fe, Ni). The agglomeration of several large particles forming a giant one could be visualised directly through the heterogeneity found in the elemental maps of such a particle.     

The distribution of fluorine and other elements in teeth using proton induced reaction analysis techniques

Proton induced gamma-ray emission (PIGE) and proton induced X-ray emission (PIXE) analysis was employed to investigate the distribution of the concentration of fluorine and ten other elements along sections of teeth samples, extracted from eight individuals. These sections which included the bulk of dentine and enamel were scanned using a proton beam of 250 m diameter. Rutberford backscattering spectra were also collected in order to obtain information about the concentration of major elements and to correct for matrix inhomogeneities.     

Comprehensive determination of trace elements in human saliva by ETA-AAS

A method is described for the comprehensive determination of a series of trace and ultratrace elements (Fe, Mn, Zn, Cu, Sr, Cr, Al and Si) in human saliva by atomic absorption spectrometry with electrothermal atomization and Zeeman-effect background correction. Procedures for sampling of total mixed saliva and its treatment including centrifugation and mineralization by HNO₃ are described in detail. To avoid the use of matrix modifiers, element standards with an artificial saliva matrix were used to construct calibration curves. Instrumental precision, tested by repeated analyses of natural salivas, is good (error less than 5%) for most elements. Lower precision was obtained for elements like Al and Si present in concentrations close to the detection limit. The analysis of some natural salivas clearly shows the influence of the sampling and treatment procedures on the reliability of the data. An accurate standardization of these procedures is thus recommended.     

Application of PIXE analysis to environmental samples stable element distribution in sea algae by scanning microprobe analysis

The resolution of a 33±3 m microprobe focussed with quadrupole doublet installed at the 3 MV Van de Graaff of the National Institute of Radiological Sciences was used for this analysis. Brown algae, Hijiki,Hizikia fusiforme was the sample target bombarded with a 2 MeV proton beam collimated mechanically into a rectangular image of 100 m × 700 m. Scanning across the sample target prepared into a longitudinal section from the caulis of the algae provided the following observations. More than 12 elements such as Al, Si, P, Cl, Ca, Mn, Fe, Cu, Zn, As, Br and Sr were determined simultaneously, together with their distributional information across the diameter. In the medullary layer, Mn and Zn were specific in their accumulation, while the deposition of Fe, Cu, As and Br were observed to be high in the epithelial layer, especially Fe and Cu which were found on the surface, where they contact ambient sea water, but no significant change in pattern was indicated for such elements as Al, P and Cl. The PIXE microprobe analysis was, therefore, effective in its detectability for elements below a few ppm level, resultantly provides further possibilities for collecting information from bio-medical and environmental samples on trace characterization of elements.