Determination of toxic elements in tea,leaves by instrumental neutron activation analysis

The concentration of certain toxic and essential elements in various brands of tea consumed locally were determined using instrumental neutron activation analysis. Transference of these elements into the drinkable portion was studied by brewing and boiling tea leaves for two minutes and the approximate intake was calculated from this data. The toxic effects of Hg, Se, As, Br and Sb are briefly discussed.     

Determination of trace elements in tea leaves by neutron activation analysis

Instrumental neutron activation analysis has been employed to determine 14 trace elements in two brands of Iranian and foreign tea. The elements are: Br, La, Ba, K, Mn, Cl, Cr, Cs, Rb, Fe, Co, Zn, Sc and Au. The transference ratio of the elements into solution, when tea is leached by percolation, is also reported. It was found that some elements are totally transferred into solution and some are partially retained by the leaves.     

Monostandard instrumental neutron activation analysis of Chinese Biological Standard Reference Material using short-lived radionuclides

A routine procedure for monostandard INAA using short-lived radionuclides with half-lives from 2 min to 15 hrs is described. Ten elements (Al, Mg, Ti, V, Mn, Cl, Na, K. Br and Cu) are determined in Chinese Biological Standard Reference Material (peach leaves). The quality of analysis was checked by analyzing the U. S. NBS Standard Reference Materials SRM-1571 and SRM-1648.     

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.     

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     

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.     

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.     

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.     

Extraction and chemical investigation of jute (Corchorus olitorius,Linn.) seed protein

Studies were made on the protein solubility of deoiled jute (Corchorus olitorius, Linn.) seed in aqueous solution over various pHs and in different concentrations of NaCl at pH 8.0. Chemical analysis of the seed protein showed 16 amino acids, of which 9 were essential. Gel filtration on Sephadex G-200 revealed the presence of four components, and their molecular weights were determined by two standard methods. Extractable jute seed proteins in salt solution were separated into six fractions electrophoretically (SDS-PAGE). The molecular weights of the six fractions were found to be 118,000; 103,000; 96,000; 67,500; 48,500; and 15,000.     

Determination of the concentrations of trace and doping elements in GaAs by neutron activation analysis

The concentrations of ten trace and dopant elements in GaAs semiconductor were determined by reactor neutron activation analysis after removal of As by evaporation of AsCl₃. The retentions of the elements of interest were measured using radiotracers. The concentrations of doping elements (Te, Cr and Zn) in commercial GaAs samples were compared to the limit of detection of these elements to analyze the possibility to use NAA for concentration depth profiling measurements. The NAA results were compared with those of electrical measurements and SIMS and the discrepancies found are discussed.     

Interaction of ozone with variable-valence metal ions in concentrated silicate solutions

Spectrophotometric studies have revealed that ozone oxidizes Cr(III) into Cr(VI), Fe(III) into Fe(VI), Mn(VI) into Mn(VII), and Np(VI) into Np(VII) in the concentrated aqueous silicate solutions. Cr(III) oxidation is accelerated in alkaline-silicate and alkaline solutions as compared to neutral silicate solution. Ferrate and permanganate ions are unstable in Na₂SiO₃ solutions (0.5–1.3 mol/L of the silicate). Neptunium(VII) ions formed in the course of ozonation are stable in Na₂SiO₃ solution (1 mol/L) upon drying in air to form solid vitreous mass.     

Properties of human parotid amylase immobilized by covalent binding to glass or sepharose or by reaction with immobilized antibody

Human parotid amylase was immobilized by covalent binding to CNBr-activated Sepharose, to Corning GAO-3940 silica glass biomaterial support by the diazonium reaction or reaction with glutaraldehyde, or as a result of the antigen-antibody reaction between rabbit antihuman parotid amylase IgG that was covalently bonded to GAO glass and soluble amylase. The amylase directly bonded to the supports showed constant activity at flow rates of 3-15 ml/min through a 1.76-cm³ (8-mm diameter) support bed, did not lose enzyme into a circulating starch solution, retained its activity in the presence of soluble antiamylase IgG, was optimally active at 35°-40°C, and lost activity at 40°-45°C. When the enzyme was bound by interaction with immobilized antibody, full activity was expressed, but some enzyme was solubilized by a circulating starch solution. Immobilization of either amylase or antiamylase IgG makes dissolution of the antigen-antibody bond difficult.     

Studies on the extraction and separation of antimony with methyl iso-butyl ketone

Systematic studies are carried out on the extraction of tri-and pentavalent antimony with MIBK from pure acid halide solutions as well as from binary mixtures of each with sulphuric acid. The influence of KI on the extraction of antimony from sulphuric acid is also investigated. It is found that the extraction of antimony halides is highly affected by addition of sulphuric acid to the aqueous phase. The extractability of some other elements at the optimum conditions for antimony extraction is also studied in order to establish separation procedures. In the light of the obtained results, analytical advantages are mentioned and separation procedures are recommended. The extraction mechanism is also discussed in order to explain the role of sulphuric acid in the extraction equilibria.     

Analytical use of proton-induced X-ray emission

Proton-induced X-ray emission, PIXE, is capable of simultaneous quantitative determination of 10–15 elements. An introduction to the physical properties of the method is given and detection limits are shown for a routine analysis of a thin aerosol sample. Examples of applications to both thick and thin samples are presented. Human tooth dentine is analysed for lead, with simple sample preparation, indicating lead values of a few ppm for Swedish children. Quantitative analyses of several other elements are obtained simultaneously. Cascade impactors are used for sampling aerosols in work environment during welding operations giving information of size distribution and concentrations of the elements present. The aerosol is dominated by particle sizes between 0.5 and 2 μm as measured by the impactor, but the size distributions are different for different elements and welding techniques and depend on the distance from the welding source. The relative abundance of the elements found in the aerosol indicates the presence of fractionation mechanisms.     

Application of TXRF for burn leach test of TRISO coated UO2 particles

A Total Reflection X-Ray Fluorescence (TXRF) methodology, employing burn-leach test, was developed to assess the quality of SiC layer in tristructural isotropic (TRISO) coated UO₂ particles prepared in BARC. The coated particles were heated at 1,123 K for about 96 h to constant weight. The calcined particles, thus obtained, were then heated in suprapure concentrated nitric acid. The supernatant was analysed for trace elements by TXRF. No uranium was detected in this supernatant solution. The study demonstrates the good quality of SiC layer and applicability of TXRF for burn leach test of TRISO coated UO₂ particles prepared.     

Computational study of the thermodynamic stabilities of hydrogen-bonded complexes in solution

Understanding of the multiple H-bonding arrays of heterocyclic compounds is essential to design effective building blocks of supramolecular polymers. We have carried out a comprehensive computational study on the thermodynamic stabilities of thirty-six H-bonded complexes with all possible H-bonding arrays in the gas phase and chloroform solvent by using M06-2X, SMD calculations and cc-pVDZ basis set. The multiple H-bonding arrays include donor acceptor–acceptor donor (DA–AD), DD–AA for the doubly H-bonded pairs, and DAD–ADA, DDA–AAD and DDD–AAA for the triply H-bonded pairs. The computational results have provided insights into the geometrical, energetic and solvation effects on the stabilities of these H-bonded complexes. The calculated free energies of association for the DD–AA (8–9) and the DDD–AAA (33–35, 36–35) H-bonded complexes are found to be inconsistent with the experimental measurements and observations that these complexes are the most strongly doubly and triply H-bonded pairs in solution, respectively, while the calculated binding free energies for all other H-bonding arrays are in good agreement with experimental values. The computational protocol can be used by practical chemists and undergraduate researchers as an efficient and state-of-the-art tool to study H-bonding interactions in supramolecular chemistry.     

The status of trace and minor elements in pulses: A PIXE measurement

The proton particle induced X-ray emission (proton PIXE) technique has been employed to study the heavy element status (essential and toxic) in five different varieties of pulses commonly cultivated and consumed in Bangladesh. In this analysis, the samples were irradiated in air with 2 MeV protons having 30 nA beam intensity for characteristic X-ray excitation. For 40 μC irradiations, the concentration of ten elements (K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Br, and Rb) was determined by comparison with a calibration obtained from the NBS orchard leaf standard, SRM 1571. In a comparative study with atomic absorption spectrophotometric (AAS) measurements of some elements in lathyrus sativus, the data were found to be in good agreement. The results obtained from the present study are discussed and compared with available data.     

A study on the solvent extraction of Hg/II/ with 2-mercaptobenzothiazole into chloroform

The extraction of mercury/II/ with 2-mercaptobenzothiazole /2-HMBT/ into chloroform has been studied. The effect of various parameters on the extraction coefficient value such as effect of pH, time of equilibration, effect of anions and cations have been evaluated. The stoichiometry of the extracted species obtained by the method of substoichiometric extraction and slope ratio method was found to be 1∶2. Decontamination factors for a number of elements in the substoichiometric extraction of Hg/II/ were also obtained.     

Tracer scale solvent extraction separation of tantalum from niobium using di-(2-ethylhexyl)-phosphoric acid as extractant

A simple solvent extraction procedure for the efficient separation of the radioactive tracers⁹⁵Nb and¹⁸²Ta from each other in a mixture using di-(2-ethylhexyl)phosphoric acid (HDEHP) as extractant is described. Tantalum was found to be quantitatively extracted from an aqueous madium, which is 1.6N in HCl and 10^?2 M in oxalic acid, with a HDEHP solution of 0.1 M concentration. Extractabilities of both niobium and tantalum in mineral acids like HCl, H₂SO₄ and HNO₃ and in some organic acids like oxalic, citric, etc., in HDEHP under the experimental conditions were also studied. The reliability of the separation procedure was verified further by γ-ray spectrometry.     

Radiochemical separation and determination of platinum,gold and palladium in complex matrices employing substoichiometric thermal neutron activation analysis

A radiochemical separation method has been developed for the separation of platinum, gold and palladium from various matrices by thermal neutron activation analysis and employing substoichiometric extractions of Pt and Au with 2-mercaptobenzothiazole and Pd with isonitrosobenzoylacetone. Decontamination factors for the individual elements after separation was also studied and was found to be greater than 10⁵ for most of the elements.