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.     

Development of a PIXE method at high energy with the ARRONAX cyclotron

The high energy PIXE (HEPIXE) method is a multi-elemental non-destructive ion beam analysis technique. It is based on the detection of the X-ray emitted due to the interaction of high energy particle beam with a sample. This technique is fast and allows the analysis of heavy and medium elements in thin (μm), thick (mm) and multilayer samples. At the ARRONAX facility (Nantes, France), the HEPIXE method has been used to determine the composition of natural and synthetic sodalites. Photochromic properties of these samples are supposed to come from the trace elements (concentration in the ppm range) present in the samples. Taking advantage of the 70 MeV proton beam available at our facility, the HEPIXE method has been also used to study multilayer samples. It has been shown that it is possible to determine the composition of each layer, their thicknesses and their depth position by analyzing the recorded X-ray spectra.     

Isolation and alpha-particle spectrometric determination of238Pu and239,240Pu in sediments

A simple method is described for the isolation and determination of plutonium isotopes in sediments. The method involves leaching of sample with nitric acid and subsequent separation of plutonium on an anion-exchange column. Major matrix elements and several potential radiochemical interferences are removed during 8M HNO₃ sample loading on the column. Thorium is removed by thorough washing with 10M HCl. Plutonium (IV) is eluted with 4M HCl. Source for alpha-particle spectrometry is prepared by LaF₃ coprecipitation technique at which stage a complete separation from uranium(VI) is also achieved. The entire analytical procedure is completed in about two days.     

Pixe analysis of powdered milk

An accelerator-based elemental study, using proton-induced x-ray emission (PIXE), was performed on four full-cream and four half-cream brands of powdered milk commonly consumed in Jordan. The elements detected in the samples are S, Cl, K, Ca, Fe, Cu, Zn, Br, and Rb. The significance of some of these elements is discussed from the viewpoint of nutrition and also their effect on milk processing and dairy technology. The standard reference milk sample, A-11, which is distributed by IAEA was also examined, and the results for trace elements detected are compared with the values certified by IAEA.     

High resolution auger electron spectroscopy for materials characterization

High resolution Auger microanalysis has become a widely applied technique in various fields of materials research. Its submicrometer spatial resolution is shown as being advantageous for surface, interface and thin film analysis. Limitations of the lateral resolution are outlined with respect to influences of electron backscattering, detection sensitivity, sample drift, beam heating and other electron induced processes. High in-depth resolution is linked with high spatial resolution for optimized depth profiling by sputtering. Crater edge profiling with scanning Auger microscopy is particularly useful for obtaining a three-dimensional microanalysis. Some examples demonstrate the capabilities and limitations in the analysis of precipitates, fracture surfaces and multilayer structures.     

A radiochemical neutron activation analysis method for the determination of tin,arsenic, copper and antimony for the forensic comparison of bullet lead specimens

Trace element characterization of bullet lead by instrumental neutron activation analysis (INAA) is hampered by the high spectral background due to antimony, normally present in high concentration in bullet lead. Tin is indicated to be a very useful element for characterization purposes. Beta-active¹²¹Sn is a suitable nuclide for quantitation of tin provided it is separated in high radiochemical purity. A radiochemical procedure capable of determining tin down to 10 ppm in bullet lead, a sequential procedure for its determination along with copper, arsenic and antimony and the application of this procedure for the determination of the contents of these elements in various bullet leads are described. This method has been applied to a “Rhinoceros shoot-out” case, referred to our laboratory.     

Triazine-modified magnetite nanoparticles as a novel sorbent for preconcentration of lead and cadmium ions

We report on a new sorbent for preconcentration of cadmium and lead ions that is based on triazine-functionalized magnetite nanoparticles that were prepared by direct silylation of magnetic nanoparticles with 3-aminopropyltriethoxysilane-2,4-bis(3,5-dimethylpyrazol)-triazine. The sorbent was characterized by IR spectroscopy, X-ray powder diffraction, scanning electron microscopy, thermal and elemental analysis. The sorbent was applied to the preconcentration of lead and cadmium ions which then were quantified by FAAS. The effects of sample pH value, extraction time, of type, concentration and volume of eluent, and of elution time were optimized. The limits of detection are 0.7 ng mL^?1 for Pb(II) ion and 0.01 ng mL^?1 for Cd(II). The effects of potentially interfering ions often found in real samples on the recovery in the determination of cadmium and lead ions in real samples were also investigated. The accuracy of the method was confirmed by analyzing the certified reference materials NIST 1571 (orchard leaves) and NIST 1572 (citrus leaves). Finally, the method was successfully applied to the determination of cadmium and lead ions in some fruit samples. Figure

We report on a new sorbent for preconcentration of cadmium and lead ions that is based on triazine-functionalized magnetite nanoparticles. After optimization of the preconcentration step the method was successfully applied to the determination of cadmium and lead ions in some fruit samples     

Proton-induced x-ray emission analysis of tea leaves

Proton-induced X-ray emission (PIXE) spectroscopy has been used for the determination of the concentration of 12 elements in tea leaves of four different brands. The elements are: Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Br, Rb and Sr. The transference ratio of the elements into solution, when tea is leached by percolation is reported. It was found that some elements are totally transferred into solution and some are partially retained by the leaves. The significance of some of the elements found in the samples is discussed.     

High resolution heat flow DSC: Application to study of phase transitions,and pore size distribution in saturated porous materials

Suitable container design permits very high temperature and differential temperature resolution in DSC even when relatively large (? 0.14 cm³) samples are used; and thus energy signals associated with phase change occurring over large temperature intervals may be analysed in differential elements. An original and powerful high resolution low temperature DSC technique (the authorsψ plot”) for studying and comparing pore size distributions (PSD) in water saturated samples (for pores having Kelvin radii between 1,2 and about 500 nm) is given, together with an application which shows that the PSD in a water saturated organic ion exchanger could be obtained from analysis of three Gaussian distributions which precisely generate a curve which is an excellent empirical fit to the recorded low temperature exotherm obtained by freezing pure water within the sample.     

Correlative organelle fluorescence microscopy and synchrotron X-ray chemical element imaging in single cells

X-ray chemical element imaging has the potential to enable fundamental breakthroughs in the understanding of biological systems because chemical element interactions with organelles can be studied at the sub-cellular level. What is the distribution of trace metals in cells? Do some elements accumulate within sub-cellular organelles? What are the chemical species of the elements in these organelles? These are some of the fundamental questions that can be addressed by use of X-ray chemical element imaging with synchrotron radiation beams. For precise location of the distribution of the elements, identification of cellular organelles is required; this can be achieved, after appropriate labelling, by use of fluorescence microscopy. As will be discussed, this approach imposes some limitations on sample preparation. For example, standard immunolabelling procedures strongly modify the distribution of the elements in cells as a result of the chemical fixation and permeabilization steps. Organelle location can, however, be performed, by use of a variety of specific fluorescent dyes or fluorescent proteins, on living cells before cryogenic fixation, enabling preservation of element distribution. This article reviews the methods used for fluorescent organelle labelling and X-ray chemical element imaging and speciation of single cells. Selected cases from our work and from other research groups are presented to illustrate the potential of the combination of the two techniques. Figure

Synchrotron X-ray fluorescence distribution maps of Ca, P and S in yeast cells. Elemental distribution maps (green color scale) were combined with the image of vacuoles labeled with Arg-CMAC (red color scale). The yellow signal of superposed images shows that Ca and P are preferentially located within the vacuole.     

Biogeochemical characterization of some continental water systems in yugoslavia by instrumental activation analysis

Trace elements in some continental water systems in Yugoslavia have been investigated by IAA. The results of the determination of trace elements are presented in this paper on the basis of the theory of concentration parameters (C_x) for the components of the rivers (dissolved materials in water, suspended and bed materials, plankton, benthos, algae, crustacea and fishes) lakes, swamps and in the soils. The investigated water system were rivers Danube, Sava, Tisa and V. Morava, lakes of Skadar, Ohrid, Dorjan, Bor, the Melenci Swamp and the soils from different regions of the Danube basin. This paper presents a short survey of our investigation of some continental water system in Yugoslavia by IAA.     

Radionuclides in the ground layer of air

This work presents the results of gamma-spectrometric analyses of 24-hour aerosol samples collected on paper filters from the ground layer of air immediately after the Chernobyl accident, from 30th April to 4th May 1986. The results obtained by using carbon filters, highly effective for adsorption of iodine isotopes, are also given.     

Improving Secondary Ion Mass Spectrometry Image Quality with Image Fusion

The spatial resolution of chemical images acquired with cluster secondary ion mass spectrometry (SIMS) is limited not only by the size of the probe utilized to create the images but also by detection sensitivity. As the probe size is reduced to below 1 μm, for example, a low signal in each pixel limits lateral resolution because of counting statistics considerations. Although it can be useful to implement numerical methods to mitigate this problem, here we investigate the use of image fusion to combine information from scanning electron microscope (SEM) data with chemically resolved SIMS images. The advantage of this approach is that the higher intensity and, hence, spatial resolution of the electron images can help to improve the quality of the SIMS images without sacrificing chemical specificity. Using a pan-sharpening algorithm, the method is illustrated using synthetic data, experimental data acquired from a metallic grid sample, and experimental data acquired from a lawn of algae cells. The results show that up to an order of magnitude increase in spatial resolution is possible to achieve. A cross-correlation metric is utilized for evaluating the reliability of the procedure. Figure

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Size fractionated impactor sampling of aerosol particles over the Atlantic Ocean from Europe to Antarctica as a methodology for source identification of Cd, Pb, Tl, Ni, Cr, and Fe

Four different samples of aerosol particles over the North Atlantic, South Atlantic, an area near the equator influenced by Saharan mineral dust, and the Antarctic Ocean were collected on board of the German research vessel Polarstern by a six stage cascade impactor system. A continental sample, typical in its size distribution pattern and heavy metal enrichment factors (relative to crust material) for industrialized areas, was used for comparison. To analyse the elements of interest, isotope dilution mass spectrometry (IDMS) using the thermal ionization technique was applied. The samples were digested with nitric acid followed by an electrodeposition of the heavy metals to be analysed in alkaline solution. Source identification could be carried out by the distribution of the heavy metals and enrichment factors on the different impactor stages using iron as a reference element for crustal origin. Two opposite types of size distribution patterns were obtained over the Atlantic Ocean. On the one hand, the main heavy metal fraction was found to be associated with the smallest particles collected on the last two impactor stages and the back-up filter with aerodynamic diameters (AD) of less than 0.95 m. This pattern together with the high enrichment factors of up to several thousand indicates combustion processes and biogenic emissions as possible sources and were typical for cadmium and lead. On the other hand, chromium and iron were preferably associated with the larger particles of >1.5 m AD. This and the low chromium enrichment factor demonstrate that the earth crust is the major source for these two elements in marine aerosol particles. Thallium and nickel could not be classified by one of these two size distribution patterns, which indicates that at least two different primary sources contribute to the content of these heavy metals in marine aerosol particles depending on the region investigated. Contrary to that, the sample collected over the Antarctic Ocean showed some significant differences. Here, a substantial amount of the total cadmium and lead was associated with the larger particles. However, relatively high enrichment factors found for cadmium, nickel, lead, and thallium in the smallest particles suggest a natural source, probably biogenic activities, in the Antarctic Ocean.Dedicated to Professor Dr. Dr. h.c. mult. J.F.K. Huber on the occasion of his 70th birthday     

The use of pre-irradiation group separations with neutron activation analysis for the determination of the rare earths in silicate rocks

The radiochemical neutron activation technique used consists of five stages; viz. sample digestion, cation exchange chromatography, irradiation and counting. Silicate samples are decomposed using a conventional hydrofluoric/perchloric acid digestion followed by loading the solutions, as chlorides, onto cation exchange resin columns. The columns are eluted with 2M HCl to remove unwanted elements and the rare earth elements are subsequently desorbed with 6M HCI. A tracer,¹⁴⁴Ce, is used to monitor the chemical yields and studies show that no fractionation or loss of any REE occurs. The REE abundances of five reference samples (NIM-G, SY-2, MRG-1, JB-1 and BOB-1) show that the described procedure is capable of providing good accuracy and precision. The method has some advantages over conventional INAA and RNAA and these are described.     

Separation of metallic impurities from uranium by anion exchange on Dowex 1×8 resin

The separation of metallic impurities from uranium by anion exchange with a Dowex 1×8 resin has been investigated. The following elements can be quantitatively separated from 400 mg uranium using a 1 cm diameter 15 or 30 cm long column. The elements Ag, Al, Ba, Ca, Cr, Cs, K, Mg, Mn, Na, Ni, Rb, REE, Sc, Th, Ti and Y can be separated by eluting the elements with conc. HCl. Uranium is retained by the resin. Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, REE and V can be separated by eluting with 0.01 N H₂SO₄. Uranium is retained by the resin. Cd and Zn can be separated by first eluting uranium with 0.5 N HCl and then eluting Cd and Zn with 1 N NH₃. Hf, Zr and V can be separated by eluting with 5 N HCl but some uranium contamination is unavoidable.     

Characterisation and comparison of biomass ashes with different thermal histories using TG-DSC

The present research is focused on the characterisation and comparison of biomass ashes from wood pellet with different thermal histories. One of the ashes is obtained in a muffle furnace until its mass stabilization reaching a temperature of 550 °C, low temperature ash (LTA); the other one came from an experimental fixed bed combustor after 4 h of stable combustion in which the temperature reached is above 1,000 °C, high temperature ash (HTA). The samples were studied using Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) techniques, and they were subjected to a heating up to 900 °C under an inert atmosphere with the objective of perceiving the differences in their thermal behaviour. At these temperatures, complex phase transformations occur, related to decomposition of carbonates and formation of silicates. TG and DSC curves are compared and some differences in mass loss, temperature peaks and enthalpy associated to endothermic effects are detected and they are explained based on the different compositions of both samples obtained at different temperatures. Other techniques were applied for the determination of the chemical composition of the ashes; X-ray fluorescence and Scanning electron microscopy with energy dispersive X-ray spectroscopy showed the elements present in the ashes, and X-ray diffraction revealed the crystalline phases and confirms that LTA is mainly composed of carbonates, while HTA mostly consists of silicates.     

Polyoxotungstate nanoclusters supported on silica as an efficient solid-phase microextraction fiber of polycyclic aromatic hydrocarbons

A highly porous silica-supported tungstophosphoric acid (PW) nanocluster was prepared for use in solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The PWs represent a class of discrete transition metal-oxide nanoclusters and their structures resemble discrete fragments of metal-oxide structures of definite size and shape. Transition metal-oxide nanoclusters display large structural diversity, and their monodisperse sizes can be tuned from several Ångstroms up to 10 nm. The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The nanomaterial was immobilized on a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. Analytical merits include limits of detection that range from 0.02 to 0.1 pg mL^?1 and a dynamic range as wide as from 0.001 to 100 ng mL^?1. Under optimum conditions, the repeatability for one fiber (n?=?3), expressed as the relative standard deviation, is between 4.3 % and 8.6 %. The method is simple, rapid, and inexpensive. The thermal stability of the fiber and the high relative recovery make this method superior to conventional methods of extraction.

The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS.     

Electron Flood Gun Damage Effects in 3D Secondary Ion Mass Spectrometry Imaging of Organics

Electron flood guns used for charge compensation in secondary ion mass spectrometry (SIMS) cause chemical degradation. In this study, the effect of electron flood gun damage on argon cluster depth profiling is evaluated for poly(vinylcarbazole), 1,4-bis((1-naphthylphenyl)amino)biphenyl and Irganox 3114. Thin films of these three materials are irradiated with a range of doses from a focused beam of 20 eV electrons used for charge neutralization. SIMS chemical images of the irradiated surfaces show an ellipsoidal damaged area, approximately 3 mm in length, created by the electron beam. In depth profiles obtained with 5 keV Ar₂₀₀₀ ⁺ sputtering from the vicinity of the damaged area, the characteristic ion signal intensity rises from a low level to a steady state. For the damaged thin films, the ion dose required to sputter through the thin film to the substrate is higher than for undamaged areas. It is shown that a damaged layer is formed and this has a sputtering yield that is reduced by up to an order of magnitude and that the thickness of the damaged layer, which increases with the electron dose, can be as much as 20 nm for Irganox 3114. The study emphasizes the importance of minimizing the neutralizing electron dose prior to the analysis. Figure

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Graft copolymers via combination of cationic polymerization and atom transfer radical polymerization and their phase separation into spherical/worm-like nanostructures

Poly(p-chloromethyl styrene)-graft-poly(methyl methacrylate) (PCMS-g-PMMA) and poly(p-chloromethyl styrene)-graft-poly(benzyl methacrylate) (PCMS-g-PBzMA) graft copolymers with asymmetric branches are synthesized via the combination of cationic polymerization and atom transfer radical polymerization (ATRP). The process involves first, the preparation of poly(p-chloromethyl styrene) (PCMS-CH₂Cl) macroinitiator without any cross-linking or side reactions through pendant benzyl chloride (?CH₂Cl) functionality by cationic polymerization using a simple FeCl₃-based initiating system at 25 °C. The as-synthesized PCMS-CH₂Cl, without any transformation, is then used as the macroinitiator to graft PMMA and PBzMA branches by ATRP to produce PCMS-g-PMMA and PCMS-g-PBzMA graft copolymers of varying compositions with controlled molecular weight and moderately narrow polydispersities (M _w/M _n?≤?1.32). The resulting PCMS₂₁ -g-PMMA₂₃₂ graft copolymer in thin film form phase separates into spherical morphology with an average diameter of 170?±?72 nm. Whereas the PCMS₂₁ -g-PBzMA₁₅₆ graft copolymer gives worm-like nanostructures with an average length of 94 nm and width of 31 nm due to phase separation as visualized through atomic force microscopy. On the other hand, the phase-separated morphology is not very well-defined for other graft copolymers (PCMS₁₁₃ -g-PMMA₂₂₇ and PCMS₁₁₃ -g-PBzMA₁₅₄) thin films containing longer PCMS chains. This approach represents a rapid and convenient route to prepare unique spherical/worm-like polymer nanostructures. Figure

Well-defined poly(p-chloromethyl styrene)-graft-poly(methyl methacrylate) (PCMS-g-PMMA) and poly(p-chloromethyl styrene)-graft-poly(benzyl methacrylate) (PCMS-g-PBzMA) graft copolymers with asymmetric branches are synthesized by the combination of living cationic polymerization and atom transfer radical polymerization (ATRP). The resulting PCMS₂₁ -g-PMMA₂₃₂ and PCMS₂₁ -g-PBzMA₁₅₆ graft copolymers phase separate into nanostructured spherical and worm-like morphologies, respectively, in thin film form. The phase-separated morphology is not very well-defined for graft copolymers (PCMS₁₁₃ -g-PMMA₂₂₇ and PCMS₁₁₃ -g-PBzMA₁₅₄) thin films containing longer PCMS chains.