Elemental and mineral characterisation of Coastal Antarctic Aerosols in snow using PIXE and SEM-EDAX

The chemical constituents of snow from a 3 m pit sampled at a coastal Antarctic site were characterised by means of PIXE and SEM-EDAX. Oxygen isotope dating revealed that the pit spanned an 8-year period, from 1986 to 1994. Concentrations measured by PIXE ranged from less than 1 ng g⁻¹ of H₂O for Cu, and Zn to several tens of ng g⁻¹ for Si, S and Cl. The major elements found were Si, S, Al, and Na, which contributed more than 75% of the element loading. Snow layers with elevated Cl concentration were regularly found along the pit. The mineralogy of the insoluble particles determined by SEM-EDAX analyses showed that quartz, plagioclase and clays were the prevalent minerals. The proportion of each element in the insoluble phase was comparable with that previously found in similar studies.     

Non-destructive analysis of coins using high-energy PIXE

At the Ionenstrahllabor (ion beam laboratory) a great variety of ions with variable energies up to several MeV/u can be produced. Performing proton induced X-ray emission (PIXE) with protons of 68 MeV, heavy elements can be detected via the K X-rays in addition to their L X-rays. The large proton range and the small absorption coefficients for the K X-rays result in an analysable depth of several millimeters. The L–K line intensity ratio yields further information on the composition of the objects. The objects of the study were so-called “Wiener Pfennige” found in Tulln, Austria. The “hoard of Tulln” contains about 11 000 of these silver coins which were strongly corroded and agglomerated to a single block. After the restoration non-destructive analysis should provide information about the elemental composition. The goal was to show the evolution of the copper content of the coins and the verification of the actual coin classification.     

Elemental analysis of agricultural soil samples by particle induced X-ray emission (PIXE) technique

In agriculture, elements essential to vital processes are also called nutrients. A suitable and reliable particle induced X-ray emission (PIXE) methodology for content determination of essential nutrients in soil samples was developed and its effectiveness proved. The PIXE method is applied to intermediate thickness samples, whose mass per area unit are smaller than 1 μg/cm². Precision and accuracy of the method was estimated after repeated measurements of a single reference material: CRM PACS-2 (estuarine sediment) with a matrix quite similar to the soil samples measured. This paper reports the results of elemental measurements in soil samples. A discussion of agricultural soil sample preparation for PIXE analysis is also presented.     

A quantitative basis for hair analysis using PIXE

The PIXE technique offers the possibility of scanning a single hair strand longitudinally with a millimetre proton beam for trace elements. However, the accuracy of the method has been questioned since the quantification of the mass concentration has been a serious problem. In this paper a specific beam-hair-detector geometry is assumed, and the correction factor accounting for the proton energy loss and the X-ray absorption in a regular hair is calculated. 43 hair segments from 8 individuals, ranging from 45 to 110 μm in in diameter were analyzed giving a mean value of 4.32% (standard deviation 0.25%) for sulphur, and a mean value of 149 ppm (standard deviation 35 ppm) for zinc. It is shown that the correction is important not only for the determination of the absolute elemental concentrations but also for the determination of their relative longitudinal distributions. The secondary corrections accounting for the inhomogeneous elemental distribution over the cross section and the irregular shape and/or the differing mass density of a hair are also calculated. It is concluded that the accuracy and precision of the PIXE method does not become considerably lower when it is applied to single hair strands, and accuracy and precision below 10% may be reached by implementing the procedure described.     

Quality control of coins mint using PIXE and RBS analysis

PIXE and RBS analysis is used to investigate the elemental content of modern Lebanese coins, in order to control their minting quality. The coins of interest were 100, 250 and 500 Lebanese Lira (LL), which are mainly bulky metals with or without coated layer. Using 3 MeV protons, proton induced X-ray emission PIXE identified and quantified elements while Rutherford backscattering spectrometry RBS checked the thickness of the coated layer. Indeed, the combination of PIXE and RBS provides a powerful tool to investigate the elemental composition of coins, either modern or ancient. In addition, the experimental protocol was checked by analyzing some other coins of known composition, such as 1-euro and 2-euro.     

Precision of PIXE analysis of thin fluid-residue specimens using internal standards

Different roles for internal standards in PIXE analysis of fluid residues are discussed. The efficacy of internal standards is predicated on having homogeneous targets of uniform thickness; the use of lecithin additives to achieve this is described and data are presented to illustrate the dependence of analytical precision on the mode of specimen preparation. Determination of actual thickness via measurement of the energy loss of transmitted protons is demonstrated; this provides a means of correcting for departures from the much-quoted “thin target” criterion.     

Total elemental composition analysis of soil samples using the PIXE technique

The determination of major and trace element contents in soils was developed by acid digestion method combined with particle-induced X-ray emission spectrometry (PIXE). The digestion of soils was achieved by using nitric acid (HNO₃), hydrochloric acid HCl and hydrogen peroxide (H₂O₂) with repeated additions. A 20 μL aliquot from the digested samples was evaporated on the Nuclepore Track-Etch Membrane and irradiated by the 2.5 MeV proton beam from the single-end type Van de Graaff accelerator. The accuracy of this methodology was estimated based on series of measurements done for a reference material of soil CRM 023-050. The proposed experimental procedure was shown to have good reproducibility of the experimental results. The corresponding limits of detection (LODs) for Na, Mg, Al, P, S, Cl, K, Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Mo and Cd were estimated. Other soil characteristics such as total carbon (TC) and nitrogen (TN) content, pH and electrical conductivity (EC) were also measured.     

PIXE analysis of Zn enzymes

Zinc is a necessary component in the action and structural stability of many enzymes. Some of them are well characterized, but in others, Zn stoichiometry and its association is not known. PIXE has been proven to be a suitable technique for analyzing metallic proteins embedded in electrophoresis gels. In this study, PIXE has been used to investigate the Zn content of enzymes that are known to carry Zn atoms. These include the carbonic anhydrase, an enzyme well characterized by other methods and the cytoplasmic pyrophosphatase of Rhodospirillum rubrum that is known to require Zn to be stable but not how many metal ions are involved or how they are bound to the enzyme. Native proteins have been purified by polyacrylamide gel electrophoresis and direct identification and quantification of Zn in the gel bands was performed with an external proton beam of 3.7 MeV energy.     

PIXE investigation of aerosol composition over the Zambian Copperbelt

Atmospheric sulphate aerosol concentrations are of interest in climate change studies because of their negative climate forcing potential. Quantification of their forcing strength requires the compilation of global sulphur emission inventories to determine the magnitude of regional sources. We report on measurements of the ambient aerosol concentrations in proximity to a copper refinery in the central African Copperbelt, along the border of Zambia and the Democratic Republic of the Congo. This region is historically regarded as one of the largest African sources of sulphate aerosols. Sulphate is produced by oxidation in the atmosphere of SO₂ emitted during the pyrometallurgical processing of Cu–Co sulphide ores. Since the last quantification of sulphur emissions (late 1960s), there has been large-scale reduction in copper production and more frequent use of the leaching technique with negligible sulphur emissions.

Samples were collected over four weeks, November–December 1996, at Kitwe, Zambia. A low volume two-stage time-resolving aerosol sampler (streaker) was used. Coarse and fine mode aerosols were separated at >2.5 and >10 μmad. Hourly elemental concentrations were determined by 3.2 MeV PIXE, and routinely yielded Si, S, K, Ca, Ti, Mn, Fe, Cu and Zn, above detection limits. Si, K, Ca and Fe (major crustal components) dominated the coarse elemental mass. In the fine stage, S and Si accounted for up to 80% of the measured mass, and S alone up to 60%. Time series analysis allowed the division of sulphur and crustal elements (Si, K, Ca, Fe) between (i) background concentrations representative of synoptic scale air masses; and (ii) contributions from local sources, i.e., copper smelter and re-suspended soil dust. Short duration episodes of S concentrations, up to 26 μg/m³, were found simultaneously with enhanced Cu, Fe and Zn. Contributions from individual pyrometallurgic processes and the cobalt slag dump could be distinguished from the elemental signatures. Periods of diminished sulphur concentrations were also identified, indicating a well-mixed regional air mass. These results will contribute towards validating global climate model predictions of aerosol forcing over central Africa.     

External-beam PIXE analysis of small sculptures

Non-destructive analysis of precious art objects is an important tool to solve provenance problems or to facilitate restoration. External beam PIXE analysis is one of the most powerful and popular methods used in this respect. The paper summarises the external beam PIXE set-up at the Accelerator Laboratory in Budapest, and two selected applications are described. Different parts of a small Cambodian metal sculpture probably made in the 11th century were analysed. It was observed that the sculpture was composed of an iron core and an outer bronze shell. This sculptural technique was well known in the Middle-East but no indication has been found about its use in the Far-East, yet. Before its restoration paint traces on a wooden relief of St. Jerome made by an unknown artist in about 1600 were analysed. Different white and red paints were distinguished at selected points and the presence of titanium on a certain part of the relief was attributed to a repainting in modern times.     

PIXE analysis of Trojan gold jewelry

Technological advancements in the production of gold jewelry from the Troad in northwest Anatolia in the third millennium BC are investigated by PIXE. Results indicate a higher percentage of Cu at the interface between joined pieces of gold than exists elsewhere on the jewelry, away from joinings. The results indicate the probable use of copper salts as a flux in the manufacture of jewelry with granulation.     

High-Energy PIXE using 68 MeV protons

The elemental composition of realistic thick samples has been measured with PIXE by 68 MeV protons. Heavy elements can be well detected much deeper below the surface, than with other methods. Measurements on objets d'art are presented. Large and complicated objects can be measured easily.     

Elemental analysis of mixed lanthanide crystals using proton-induced K X-ray emission

A 3.2 MeV external proton beam K X-ray PIXE (particle-induced X-ray emission) facility has been constructed with the special aim of performing accurate and multi-elemental analysis of aqueous crystals containing mixtures of lanthanide compounds. Minimum detection limits and the problems of photon backscattering within the sample matrix are discussed in detail. The accuracy of the method was validated via comparison to commercial instrumental neutron activation analysis and to a new high performance liquid chromatography method; both of which were performed at independent laboratories. The values for the ratio $\text{La}\text{(}\text{La}\text{+}\text{Ce}\text{)}$, in a series of mixed crystals, were applied to a low temperature investigation of crystal field splittings.     

Quantitative PIXE analysis of human uterine myoma

Twenty-two samples, taken from eight pathological proved uterine myoma patients, were embedded in paraffin and cut into slices of identical thickness (4.0 μm). After deparaffinization, washing and drying, the slices of myomal tissue and their neighboring myometrial tissue were bombarded by 2.0 MeV proton beams from a 3 MV Van de Graaff accelerator. The induced characteristic X-rays were then detected and analyzed using a HPGe detector system. The absolute concentrations of trace elements contained in tumors and normal tissues of human myomal uterus were determined, in reference to a known concentration of doped yttrium. Significant correlations between the concentration of elements, both in tumors and in normal tissues, were found.     

PIXE analysis of ancient Chinese Changsha porcelain

In this work, proton induced X-ray emission (PIXE) method was applied for the analysis of ancient Chinese Changsha porcelain produced in the Tang dynasty (AD 618–907). A collection of glazed potsherds was obtained in the complex of the famous kiln site at Tongguan, Changsha city, Hunan province. Studies of elemental composition were carried out on ten selected Changsha potsherds. Minor and trace elements such as Ti, Mn, Fe, Co, Cu, Rb, Sr, and Zr in the material of the porcelain glaze were determined. Variation of these elements from sample to sample was investigated. Details of results are presented and discussed.     

A PIXE micro-tomography experiment using MLEM algorithm

A new approach for PIXE tomography has recently been introduced by our group. The reconstruction program is based on the maximum likelihood expectation maximization (MLEM) algorithm. Since the algorithm is built upon the actual stochastic model of X-ray production and propagation, attenuation correction as well as ion energy loss are readily incorporated into the reconstruction. The resultant procedures have been previously tested by using simulated X-ray yields and the results were given in an earlier paper. In this work, we present the results of the tomographic reconstruction of a realistic sample done in order to study the effectiveness of the algorithm.     

Characterization of human fingernail elements using PIXE technique

PIXE technique was employed in the determination of the major, minor and trace elemental concentrations in finger-nails of 62 healthy young adults (30 females and 32 males), aged between 20 and 37 years. The elemental concentrations in the nails of the analyzed population provide good reference data set for further health studies. The PIXE measurements were carried out using 1.8 MeV collimated proton beam from the 2.5 MV AN-2000 Van de Graaff accelerator at INFN, LNL, Legnaro (Padova), Italy. The results show the presence of twenty elements. Their metabolic roles in humans are presented and discussed. The comparison of our results with those of other authors are also presented.     

应用PIXE分析胎儿肝、脑、肾、肺组织及其亚细胞组分中的元素分布

质子激发X射线荧光(PIXE)分析了上海市6例自然流产胎儿(5—6个月)的肝、脑、肾、肺的组织匀浆及其线粒体、溶酶体和微粒体中K、Ca、Mn、Fe、Cu、Zn、Pb、Rb、Sr的含量。结果显示了元素在不同脏器的分布以及同一脏器的亚细胞水平的分布,并且通过与成年人肝的数据比较,得出胎儿中必需微量元素Zn、Cu、Fe等含量显著高,并且有的亚细胞分布模式也不同,这一结果提示了必需微量元素的亚细胞分布与细胞发育有密切关系。     

Micro-crystalline inclusions analysis by PIXE and RBS

A characteristic feature of the nuclear microprobe using a 3 MeV proton beam is the long range of particles (around 70 μm in light matrices). The PIXE method, with EDS analysis and using the multilayer approach for treating the X-ray spectrum allows the chemistry of an intra-crystalline inclusion to be measured, provided the inclusion roof and thickness at the impact point of the beam (Z and e, respectively) are known (the depth of the inclusion floor is Z + e). The parameter Z of an inclusion in a mineral can be measured with a precision of around 1 μm using a motorized microscope. However, this value may significantly depart from Z if the analyzed inclusion has a complex shape. The parameter e can hardly be measured optically. By using combined RBS and PIXE measurements, it is possible to obtain the geometrical information needed for quantitative elemental analysis. This paper will present measurements on synthetic samples to investigate the advantages of the technique, and also on natural solid and fluid inclusions in quartz. The influence of the geometrical parameters will be discussed with regard to the concentration determination by PIXE. In particular, accuracy of monazite micro-inclusion dating by coupled PIXE-RBS will be presented.