Trace element determination in tomato puree using particle induced X-ray emission and Rutherford backscattering

Particle induced X-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS) were used to determine the concentrations of trace elements in samples of 12 tomato puree brands sold in the Mexican market. While RBS offered information about the main elements present in the matrix, PIXE gave results on trace elements. As a whole, data for 17 elements (C, N, O, Na, Mg, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, and Zn) were obtained. To evaluate the results, a comparison with brands from USA, Japan, Colombia, and Chile was carried out, using tomato purees produced following the domestic technology recipe. Additionally, the results were considered in the light of the Codex Alimentarius and the Mexican standard. It was found that all of the brands fall within the limits established by these standards, being of the same order of magnitude as the foreign brands. This revised version was published online in July 2006 with corrections to the Cover Date.     

Usefulness of nuclear and atomic-based analysis techniques in air pollution studies in Nigeria

Three nuclear and atomic-based techniques for elemental analysis of air-particulate samples are discussed in terms of their usefulness in an environmental monitoring and impact assessment programme, supported by the European Economic Community, in Nigeria. Instrumental neutron activation analysis (INAA) and proton induced X-ray emission (PIXE) analysis are compared with respect to the number of elements detected and the detection limits obtained for air-particulate matrices. The latter is used in conjunction with Rutherford backscattering spectrometry (RBS) in order to correct for variations in matrix composition. A scanning electron microprobe (SEM) with analytical facilities is also employed mainly for characterization of the air-particulates through measurement of particle size and morphology. The value of carrying out statistical analysis for differentiating between collection sites or sources of pollution is emphasised. Reference to results obtained from the analysis of air-particulates collected during the Harmattan season at Kano and Ife, separated by about 1000 km place the problem in context and serve to illustrate the requirements.     

External proton beam analysis of layered objects

Ion-beam analysis for determining the elemental composition and to obtain depth information has been carried out with MeV protons in air by means of simultaneous external PIXE and RBS. Stainless steel products of extended size and a historic painting are analyzed non-destructively. These objects include systems of layers with areal densities up to some ten mg/cm(2). Depth information is obtained by PIXE using energy variation of the primary proton beam and in addition directly from RBS for the outermost near-surface region. Main and secondary elements as well as impurities can be determined together with areal densities. Particularly, the knowledge on the depth distribution of the pigments in paintings provides information on paint techniques.     

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.     

Elemental composition of hypertrophic scar and normal skin tissue using proton induced X-ray emission

Hypertrophic scars are a particular type of scar that can form after any type of dermal trauma. They are unsightly, red and elevated above normal skin level. At present no-one knows why these scars form and what form the treatment should take. Full thickness hypertrophic skin tissue as well as full thickness normal skin samples, obtained form the Restoration of Appearance and Function Trust (RAFT), Institute of Plastic Surgery, Mount Vernon Hospital, were analysed, using simultaneously both PIXE and RBS, with a 2 MeV proton beam. The epidemis was compared to the dermis on both normal and scarred tissue, and each was compared to the other, to see if there were any variations in elemental composition. In all the samples C, N and O detected by RBS and P, S, Cl, K, Ca, Fe detected by PIXE were found, In the majority of samples Zn and Cd were found, and in a few samples Sn was determined. Significant differences in concentrations, for the elements P, S, K and Cd, between the epidermis and dermis in both hypertrophic scarred and normal skin tissue were found. A difference was also detected between elemental concentrations in normal and scarred skin for the elements Ca, P, S, Fe and Cd.     

External proton beam analysis of layered objects

Ion-beam analysis for determining the elemental composition and to obtain depth information has been carried out with MeV protons in air by means of simultaneous external PIXE and RBS. Stainless steel products of extended size and a historic painting are analyzed non-destructively. These objects include systems of layers with areal densities up to some ten mg/cm². Depth information is obtained by PIXE using energy variation of the primary proton beam and in addition directly from RBS for the outermost near-surface region. Main and secondary elements as well as impurities can be determined together with areal densities. Particularly, the knowledge on the depth distribution of the pigments in paintings provides information on paint techniques.     

Determination of Ca, P, Sr and Mg in the synthetic biomaterial aragonite by NAA

Implanted ⁷⁴Ge and ¹²⁰Sn concentrations in silicon (Si) layers were investigated by particle induced X-ray emission (PIXE), instrumental neutron activation analysis (INAA), Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS). Slight differences were observed in the results obtained. It was shown that PIXE and INAA are as powerful as the traditional RBS and SIMS spectroscopy for the investigation of thin layered Si.This revised version was published online in November 2005 with corrections to the Cover Date.     

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.     

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     

Elemental composition of skin tissue by PIXE and INA analyses

Hypertrophic scars are a particular type of scar that can form after any type of dermal injury. They are unsightly, red, elevated above nomal skin level, itchy and painful. At present no-one knows why these scars form. Due to the differences between scar tissue and normal skin it was decided to analyse skin tissue which at a later date would be compared to scar tissue. Split skin graft (epidemis) samples as well as full thickness skin (epidemis to demis) tissue were analysed using PIXE and RBS with a 2 MeV proton beam. The epidemis was compared to the demis to see if there were any variations between the two. In all the samples P, S, Cl, K, Ca, Fe, and Cd were detected and in a majority of the samples Zn and Ba were found, using PIXE. It was found that, between the epidemis and demis, there was an significant increase in P in the epidermis in both full thickness and split skin graft samples. Complementary elemental analysis was also performed using neutron activation, and Br, Na and Zn were detected.     

Ion-beam analysis of CuInSe<Subscript>2</Subscript> solar cells deposited on polyimide foil

CuInSe₂ (CIS) solar cells deposited on polyimide foil by the Solarion company in a web-coater-based process using sputter and evaporation techniques were investigated in the ion beam laboratory LIPSION of the University of Leipzig by means of Rutherford backscattering spectrometry (RBS) and particle-induced X-ray emission (PIXE) using high-energy broad ion beams and microbeams. From these measurements the composition of the absorber and the lateral homogeneity and film thicknesses of the individual layers could be determined on the basis of some reasonable assumptions. For the first time, quantitative depth profiling of the individual elements was performed by microPIXE measurements on a beveled section prepared by ion-beam etching of a CIS solar cell. Within the CIS absorber layer no significant concentration–depth gradients were found for Cu, In, and Se, in contrast with results from secondary neutral mass spectrometry (SNMS) depth profiling, which was applied to the same samples for comparison. Furthermore, both PIXE and SNMS showed the presence of a remarkable amount of Cd from the CdS buffer layer in the underlying absorber.     

Preparation and characterization of a new set of IAEA reference air filters using instrumental neutron activation analysis, proton-induced X-ray emission and Rutherford backscattering

A new set of reference air filters was prepared for proficiency testing of laboratories involved in air pollution studies organized by the International Atomic Energy Agency (IAEA). The set consists of one filter loaded with airborne particulate matter (APM) and one blank filter. Target values and their standard deviations were established using instrumental neutron activation analysis (INAA) and proton induced X-ray emission (PIXE) with proven accuracy. Rutherford backscattering (RBS) was used to help in deriving the necessary corrections in PIXE. Losses of individual elements from APM due to the wet deposition procedure were evaluated.     

The analysis of air particulate deposits using 2 MeV protons

Particle-induced X-ray emission (PIXE) analysis of the lighter elements in time-resolved air particulate deposits has been carried out. Minimum detection limits have been determined for 1.0, 2.0 and 3.5 MeVprotons. Quantitative PIXE analysis results, obtained with 2 MeV protons, are given for temporal variations in the elemental concentrations of Na, Al, Si, S, Cl, K, Ca and Fe. Rutherford backscattering (RBS) spectra were taken simultaneously with the PIXE spectra to provide information on lead concentrations and deposit thicknesses. The experimental problems associated with the quantitative analysis of light elements on cellulose acetate filters are described. The relationship between these results and meteorological data is discussed.     

A Positron Emission Tomography Analysis of Glucose Metabolism in Alzheimer's Disease Brain Using [18F] Fluorodeoxyglucose: A Parallel Study with Elemental Concentrations

Alzheimer's disease (AD) is a debilitating form of dementia which leads to impaired memory, thinking and behavior. This work examines elemental concentrations between "normal" and AD subjects as well as the hemispherical differences within the brain. Tissue samples from both hemispheres of the frontal lobe in both AD and normal subjects were examined for their trace element concentrations using PIXE and RBS analyses. Elemental concentrations were seen to differ between AD and normal brain tissue samples. While in the normal group concentrations were found to be significantly higher in the right hemisphere than in the left the converse was true in AD. A change in elemental concentrations may indicate possible alterations in the function of the blood brain barrier. This was examined by determining regional cerebral metabolic rates of glucose (rCMRGlu) using the in vivo technique of positron emission tomography (PET). Again variations between both hemispheres and between AD and normal were found.     

Analyse von Schichten und Schichtsystemen mit hochenergetischen Ionenstrahlen

Summary The utility of energetic ion beams for thin film analysis is reviewed briefly. The different methods for analysis are based on the different interactions of the fast ions with atomic nuclei and electrons of the solid state samples to be analysed. These interactions include not only ion scattering, but also emission of x-rays and nuclear reactions. Quantitative chemical analysis with good depth resolution by Rutherford-backscattering analysis (RBS) is demonstrated for the suicide formation at the interface between Si and metal. Particle induced x-ray emission (PIXE) can be used for the detection of small amounts of impurities (atomic number Z 6). In addition, light elements can be detected within a heavy matrix using ion beams for nuclear reaction analysis (NRA). The different ion beam methods are compared and their advantages are discussed with respect to different analytical problems. In addition, channeling experiments on epitaxial superlattices are presented which allow the determination of the strain individual interfaces.     

Non-destructive 3D-characterization of Zn 2-2x Cu x In x S 2-thin films with ion beam analysis

Thin layers of ZnS-CuInS(2) mixed crystals (called ZCIS) are promising absorber materials for thin film solar cell applications. The ZCIS-films investigated in this study were grown on (001)GaP, SiO(2) and CeO(2)/Al(2)O(3) with different elemental compositions by Pulsed Laser Deposition (PLD). In order to optimize the sample preparation process a quantitative three-dimensional (i.e. laterally and depth resolved) determination of the compositions and thicknesses of the ZCIS-films is needed. It is demonstrated how this difficult analytical task can be addressed with ion microbeam analysis. For this purpose the films have been analysed non-destructively by means of Rutherford Backscattering Spectrometry (RBS) and Particle Induced X-ray Emission (PIXE) using a 2 MeV He(+) ion microbeam at the high-energy ion nanoprobe LIPSION. A large variation in film thickness caused by particulates deposited on the film was observed. The elemental compositions of the film and the particulates have been determined and compared with the target composition. The deviations found varied substantially for the individual elements. It could be concluded from these measurements, that the quality of the sintered PLD-target is of crucial importance for the roughness of the films. Furthermore concentration-depth-profiles of the individual elements have been derived non-destructively by means of RBS.     

PIXE-RBS combination to measure uranium and thorium in environmental and biological samples

A combination of two techniques, PIXE (particle induced x-ray emission) and RBS (Rutherford backscattering), is proposed as an analytical tool to measure uranium and thorium in environmental and biological samples and in the study of the micro-distribution of uranium is low Z matrices such as biological tissue.Work supported by U.S. Department of Energy Contracts DE-AC02-76CH-00116 (MC, KWJ) and DE-AC02-76EV-00119 (NPS, MEW). One of us (ASP) is grateful to FINEP (Financiadora de Estudos e Projetos) and CNPq (Conselho Nacional de Desenvolvimento Cientifico e Technológico).     

Trace element analysis of placentas of alcoholics and controls with external beam PIXE

External beam PIXE analysis with a protonbeam of 2.4 MeV was used to study trace element concentrations in human placentas. The aim was to check the suitability of PIXE analysis regarding soft tissue samples. Sample preparation was kept as simple as possible to avoid contamination or losses due to volatilization. The element of interest /Fe, Cu, Zn, Se, Br, Rb, and Sr/ were easily detected. A comparison was made with placental samples of alcoholics and abstinent controls to determine whether trace element concentrations in the placenta play a role in the pathogenesis of fetal alcohol syndrome.     

Comparative composition analysis of SiOx and SiNx thin films by AES,EDX and RBS

The chemical composition of thin films in SiO_x and SiN_x systems (“SIPOS”) have been analyzed by comparative AES, EDX, and RBS of the same samples to assess the extent of possible errors introduced by the “weak points” of each method. These exist for EDX in the necessity of a thickness correction, for AES in a possible composition dependence of the sensitivity factors, and for RBS in the low sensitivity in detecting light elements. Linear correlations between the data obtained by RBS and EDX have been revealed over the whole range of x. Therefore, EDX can be calibrated by appropriate standards of pure SiO₂ or Si₃N₄ films. For AES analysis a calibration curve is needed. Using RBS data for calibration the content of the light components O and N might be slightly overestimated by this method.     

Trace element analysis of maternal scalp hair by external beam proton-induced X-ray emission (PIXE)

We have constructed an external beam proton-induced X-ray emission (PIXE) system for trace element analysis of biological and environmental samples. Optimization of sample preparation and experimental PIXE set up has produced a rapid, accurate, sensitive, and reliable PIXE analysis procedure. The analytical procedure was evaluated using maternal scalp hair from pregnant women 16–19 weeks' gestation. The samples were irradiated with 3.5 MeV protons from the Rutgers Nuclear Physics Department's 8 MV Tandem FN Van de Graaff accelerator. The concentrations of the elements calcium (Ca) to cadmium (Cd) in hair are reported for 50 subjects. The analytical procedure is suitable for non-invasive clinical analysis for evaluation of nutritional states and for environmental exposure to toxic metals.