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Abstract  

We present a NAA method to determine ultratraces of K, Th, U and other trace impurities in liquid organic scintillators, which are known as ultrapure detector materials for neutrino or dark matter experiments. A combined optimization of relevant factors for sensitive NAA has been realized, leading to a sensitivity for U down to 10−16g/g. Samples of 250 ml have been irradiated up to 120 h at a thermal neutron flux of 5–8·1012·n·cm−2·s−1. Acidic extraction, wet ashing and TBP-extraction are used for radiochemical separations. Finally, coincidence techniques are applied for increased sensitivity.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: N. Tsibakhashvili, L. Mosulishvili, E. Kirkesali, I. Murusidze, M. Frontasyeva, S. Pavlov, I. Zinicovscaia, P. Bode, and Th. van Meerten

Abstract  

Instrumental neutron activation analysis was used to study accumulation of Hg(II) and Cr(VI) ions in Arthrobacter globiformis 151B, a gram-positive, Cr(VI)-reducer aerobic bacterium isolated from basalt sample taken from the most polluted region in the Republic of Georgia (Kazreti). Experiments were focused on (1) accumulation of Hg(II) in bacterial cells; (2) accumulation of Cr(VI) in A. globiformis 151B in the presence of Hg(II) and (3) effects of Hg(II) and mixture of Cr(VI)–Hg(II) on the elemental composition of bacteria. It was shown that this bacterial strain possesses uptake mechanisms by which mercury toxicity can be reduced in environment and that accumulation of Cr(VI) in A. globiformis 151B is much higher in the presence of Hg(II) ions. Accumulation of Hg(II), similar to the Cr(VI) accumulation, follows well the Lengmuir–Freundlich model. NAA measurements showed increased content of Fe in bacteria under Hg and Cr action, suggesting that Fe-containing biomolecules play a decisive role in detoxifying of heavy metals by A. globiformis 151B. A concentration of 5000 μg/L of Hg(II) was found to be critical for A. globiformis 151B. At this concentration of Hg(II) the concentrations of both essential (Na, Mg, Al, Cl, K, Mn, Zn) and some non-essential elements (Rb, Sb, Sc, As) changed drastically along with a decrease of the biomass of bacteria by a factor of two. One may assume that under this high exposure to Hg(II) the structure of the bacterial cell wall was destroyed.

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Abstract  

The k 0-standardization method of NAA is known as one of the most remarkable progress of NAA with its many advantages. Recently, our laboratory is highly involved in various areas of application of k 0-NAA. This paper focuses on the application of the k 0-NAA method in Nutritional and Health-Related Environmental field. Tobacco holds a leading position among different commodities of human consumption. The adverse health effects of toxic and trace elements in tobacco smoke on smokers and non-smokers are a special concern. In the present study, the concentration of 24 trace elements in cigarette tobacco of five different brands of Algerian and American cigarettes have been determined by k 0-based INAA method. The results were compared with those obtained for samples from Iranian, Turkish, Brazilian and Mexican cigarettes tobacco. To evaluate the accurate of the results the SRM IAEA-140/TM was executed. The analytical results showed that the relative error of most of the elements was less than 10%.

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Abstract  

A suite of shallow and deep subsurface waters from southwestern Illinois has been analyzed for chlorine (CT), bromine (Br), and sodium (Na+) using three different methods. Cl and Br were analyzed by ion chromatography (IC) and neutron activation analysis (NAA). Na was analyzed using inductively coupled plasma-atomic emission spectrometry (ICP-AESS) and NAA. In addition, five water standards were prepared with compositions over the range of Cl, Br, and Na concentrations in the natural waters were analyzed using the same methods. Analytical results for the prepared standards by the different methods were in good agreement. However, analytical results on natural waters yielded generally poor agreement between the methods. Our results suggest that solute concentrations and ratios between major solutes in subsurface waters determined by IC and ICP-AES may involve substantial laboratory error.

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Abstract  

Without quality historical records that provide the composition of legacy materials, the elemental and/or chemical characterization of such materials requires a manual analytical strategy that may expose the analyst to unknown toxicological hazards. In addition, much of the existing legacy inventory also incorporates radioactivity, and, although radiological composition may be determined by various nuclear-analytical methods, most importantly, gamma-spectroscopy, current methods of chemical characterization still require direct sample manipulation, thereby presenting special problems with broad implications for both the analyst and the environment. Alternately, prompt gamma activation analysis (PGAA) provides a ‘single-shot’ in-situ, non-destructive method that provides a complete assay of all major entrained elemental constituents.1–3 Additionally, neutron activation analysis (NAA) using short-lived activation products complements PGAA and is especially useful when NAA activation surpasses the PGAA in elemental sensitivity.

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Abstract  

Neutron-flux behaviour during irradiation should be known when applying the ko-method of neutron activation analysis /NAA/. During two 100-hour operating periods of the TRIGA MARK II reactor, Ljubljana, the flux was measured by means of a197Au/n,/198Au monitor /E=411.8 keV/. Cadmium-covered irradiations were also performed to obtain the epithermal flux and thermal-to-epithermal flux ratio variations. Consistency was found between these results and the reactor operators' logbook record.

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Abstract  

A biochemical technique was used to separate three kinds of proteins (albumin, globulin and gliadin) in corn samples from high selenium areas and normal areas in Erxi autonomous region of Hubei Province, China. The contents of Se and other elements in these proteins were determined by neutron activation analysis (NAA). The results show that Se is enriched in corn proteins at high selenium area, while Cu, Al, Mn, V and Cl are also enriched in varying degrees.

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Abstract  

The concentrations of extractable organohalogens (EOX) and extractable persistent organohalogens (EPOX) in placenta, umbilical cord and hair of mothers delivering disabled or normal newborns as well as the compositions of EPOCl in three analyzed matrices were determined by a combination of NAA, gas chromatography and chemical separation. The results indicated that both EOX and EPOX decreased in the order: hair > umbilical cord > placenta. Organochlorines were the major fraction of organohalogens. More than 77% of EPOCl were unidentified. High organohalogens exposure may induce adverse health effects, and hair, as a biomonitor for organohalogens assessment, is more recommendable.

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Abstract  

The neutron activation analysis (NAA) was applied to the multielement analysis of the mediterranean fruit fly, Ceratitis capitata Wied., taken from a stock produced at the Tropical Scientific Research Institut (IICT) in Lisbon, and to its artificial food. Dry samples were irradiated in the OSIRIS reactor, within a work performed at the Laboratoire d'Analyse par Activation Pierre Süe (CEA/CEN-Saclay). The contents of Ca, K, Mg, Cl, Na, Fe, Zn, Al, Mn, Ba, Rb, Br, Co and Cs for the cases of Ceratitis capitata Wied. eggs, larvae, pupae, males and females and of its artificial food are reported.

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Abstract  

The definitions used for the k0-constant, the coincidence correction factorc and the detector efficiency f in the k0-method for NAA provide no means to interprete or correct for interference by artificial peaks. In this paper, extended descriptions for the detector efficiency are proposed to deal with escape peaks. For sum peaks caused by true coincidence, a k1-constant is defined as an alternative for the k0-constant, by separating the k0 into a part related to activation and a part related to spectrometry. The k1-constant is based on experimental data, just like the k0-constant.

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