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.     

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 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.     

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.     

用质子激发X射线分析方法进行人发微量元素的分析研究

一、序言 质子激发X射线分析方法是瑞典人约翰逊在1970年首先提出来的。由于它具有灵敏度高、取样少、无损伤、快速、适用范围广等特点,使它在十余年中在生物医学、环境科学、地质、冶金、考古学和法学等领域得到了广泛的应用。我们应用质子激发X射线分析方法分析了人发中的微量元素。     

PIXE analysis of biological bodies in Uranouchi bay

We have investigated shellfish called Japanese littleneck clam (Ruditapes philippinarum) which were collected from Uranouchi bay (Kochi, Japan) for analysis of elemental concentration by Particle Induced X-ray Emission (PIXE). A 4 MeV He⁺⁺ ion beam was used to analyze shellfish in the ion beam laboratory of Kochi University of Technology (Japan). In the present study, shellfish have been chosen as a representative of the biological bodies in the Uranouchi bay. The concentration of heavy metals in shellfish has been quantified and the results are compared with those obtained by analyzing Market shellfish. Analyzing shellfish collected from three different places in the bay Cu, Zn, Br, Sr and Zr are detected as heavy metals. Our results suggest that in comparison with Market shellfish the Uranouchi bay shellfish contain more heavy metals.     

PIXE analysis of nephrite minerals from different deposits

External-beam PIXE was used to determine the major, minor and trace elements of 45 nephrite minerals from 14 different deposits, including China and other countries. Depending on the R^∗ value (mole percent of Mg²⁺/(Mg²⁺ + Fe²⁺⁽³⁺⁾)) and content of Cr, Co and Ni, two types of nephrite minerals from dolomite and serpentinized ultramafic deposits can be more accurately distinguished. Besides, the nephrite minerals from Xiaomeiling and Wenchuan deposit can be distinguished with others from dolomite deposits, through the content of Sr and Mn/Fe value, respectively. Moreover, depending on the Sr content, clear evidence was given to prove that the raw materials of ancient nephrite artifacts from Liangzhu culture ruins are not from Xiaomeiling nephrite deposit. Furthermore, PIXE as a non-destructive method will be more used to study ancient nephrite artifacts, so these results can provide scientific basis for seeking the provenance of nephrite raw materials.     

两次PIXE国际横向比对分析结果

介绍了两次ＰＩＸＥ国际横向比对中实验方案的设计思想，对一些具体问题的解决办法以及定量分析中的质量保证和质量控制的实施情况。     

PIXE analysis of high Z complex matrices

The study of complex materials (nonhomogeneous matrices containing medium and/or heavy atoms as major elements) by PIXE requires the tailoring of the experimental set up to take into account the high X-ray intensity produced by these main elements present at the surface, as well as the expected low intensity from other elements “buried” in the substrate. The determination of traces is therefore limited and the minimum detection limit is generally lower by at least two orders of magnitude in comparison with those achievable for low Z matrices (Z20). Additionally, those high Z matrices having a high absorption capability, are not always homogeneous. The nonhomogeneity may be, on the one hand, a layered structure (which is uneasy to profile by RBS if the material contains elements of neighbouring masses or if the layered structure extends on several microns) or, on the other hand, inclusions which are to be localized. PIXE measurements at various incident energies (and with various projectiles (p, d, He³, He⁴)) are then an alternative method to overcome those difficulties. The use of special filters to selectively decrease the intensity of the most intense X-ray lines, the accurate calculation of the characteristic X-ray intensity ratios (K/Kβ, L/Lβ) of individual elements, the computation of the secondary X-ray fluorescence induced in thick targets are amongst the most important parameters to be investigated in order to solve these difficult analytical problems. Examples of Cr, Fe, Ni, Cu, Ag and Au based alloys with various coatings as encountered in industrial and archaeological metallurgy are discussed. RBS, PIGE and NRA are sometimes simultaneously necessary as complementary (or basic) approaches to identify corroded surface layers.     

Golden glazes analysis by PIGE and PIXE techniques

We present the analysis performed on the chemical composition of two golden glazes available in the market using the PIGE and PIXE techniques at the ITN ion beam laboratory. The analysis of the light elements was performed using the Emitted Radiation Yield Analysis (ERYA) code, a standard-free method for PIGE analysis on thick samples. The results were compared to those obtained on an old glaze. Consistently high concentrations of lead and sodium were found in all analyzed golden glazes. The analysis of the samples pointed to Mo and Co as the specific elements responsible of the gold colour at the desired temperature, and allowed Portuguese ceramists to produce a golden glaze at 997 °C. Optical reflection spectra of the glazes are given, showing that the produced glaze has a spectrum similar to the old glaze. Also, in order to help the ceramists, the unknown compositions of four different types of frits (one of the components of glazes) were analysed.     

PIXE spectrum analysis taking into account bremsstrahlung spectra

Continuous background appearing over the wide region of X-ray energy in the PIXE spectrum is very troublesome presence in the peak fitting. In the usual manner, the spectrum of continuous background is predicted as a function of polynomial and is subtracted from the X-ray spectrum. However, the parameters of the polynomial are determined with difficulty in the case that the continuous background exists under many peaks of characteristic X-rays. We calculated the production cross sections of continuous X-rays for several elements on the basis of the theories of quasi-free electron bremsstrahlung (QFEB), secondary electron bremsstrahlung (SEB) and atomic bremsstrahlung (AB), and obtained the continuous X-ray spectrum as a function of atomic number and X-ray energy. X-ray spectra of a standard sample and of a bovine liver sample were analyzed by a pattern analysis method assuming the reference spectra consisting of characteristic X-rays and continuous X-rays for each element. The results of analysis are quite satisfactory. By the present method, the PIXE spectra can be analyzed under little influence of the background subtraction, and it enables us a full auto-analysis of PIXE spectrum.     

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.     

Thick target PIXE analysis of clays for archaeological studies

In view of the study of trade and cultural exchange in Western Africa during the Middle-Ages, ceramics from this region will be analyzed by PIXE in order to localize the production areas via the chemical composition of the clays used for the fabrication of the pottery. To check the analytical method the concentrations of some 20 elements in the Perlman-Asaro standard pottery are determined. The results are compared to the values reported by others.     

Elemental investigation of Syrian medicinal plants using PIXE analysis

Particle induced X-ray emission (PIXE) technique has been employed to perform elemental analysis of K, Ca, Mn, Fe, Cu, Zn, Br and Sr for Syrian medicinal plants used traditionally to enhance the body immunity. Plant samples were prepared in a simple dried base. The results were verified by comparing with those obtained from both IAEA-359 and IAEA–V10 reference materials. Relative standard deviations are mostly within ±5–10% suggest good precision. A correlation between the elemental content in each medicinal plant with its traditional remedial usage has been proposed. Both K and Ca are found to be the major elements in the samples. Fe, Mn and Zn have been detected in good levels in most of these plants clarifying their possible contribution to keep the body immune system in good condition. The contribution of the elements in these plants to the dietary recommended intakes (DRI) has been evaluated. Advantages and limitations of PIXE analytical technique in this investigation have been reviewed.     

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.     

PIXE analysis of obsidian tools from radiocarbon dated archaeological contexts

Obsidian tools from archaeological sites in Turkey and Southern Italy, ¹⁴C-AMS dated to the Neolithic were submitted to IBA analyses at CEDAD, University of Salento, Italy. PIXE and PIGE quantitative analysis of major and trace elements allowed the separation of the samples in different compositional groups corresponding to different sources of obsidian, identified on the basis of published data.     

Non-destructive analysis and appraisal of ancient Chinese porcelain by PIXE

This paper reports the results of the PIXE analysis on ancient Chinese blue and white porcelain fired at Kuan Kiln (Jingdezhen, Jiangxi province) during 13–19th century. The major, minor and trace element of porcelain body, white glaze and blue glaze were determined by PIXE. In this paper the chemical compositions of porcelain body, white glaze and blue glaze measured from Yuan (AD 1206–1368), Ming (AD 1368–1644) and Qing (AD 1616–1911) blue and white porcelain are present. The cobalt blue pigment used in Yuan, Ming and Qing are also discussed.