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Abstract  

An extensive database of analytical results from a recent biological matrix Reference Material Characterization Campaign permitted an intercomparison of the performances of various methods among each other and with "true" best estimate concentration values established for these materials. Six different variants of neutron activation analysis (NAA) methods were employed including: instrumental neutron activation analysis, instrumental neutron activation analysis with acid digestion, neutron activation analysis with radiochemical separation, neutron capture prompt gamma activation analysis, epithermal instrumental neutron activation analysis, and neutron activation analysis with preconcentration. The precision and accuracy performance of NAA-based analytical methods are compared with three other major techniques, atomic absorption spectrometry (AAS), atomic emission spectrometry (AES) and mass spectrometry (MS) for 28 elements in 10 natural matrix materials.

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Abstract  

The k 0-IAEA program developed for implementation of the single comparator instrumental neutron activation analysis method (k 0-INAA) has been used for elemental analysis with NIRR-1 irradiation and counting facilities. The existing experimental protocols for routine analysis based on the relative method were used to test the capability and reliability of the program for the analyses of geological and biological samples. The Synthetic Multi-element Standards (SMELS) types I, II and III recommended by the international k 0 user community for the validation of k 0-NAA method in NAA laboratories, furthermore, the following standard reference materials: NIST-1633b (Coal Fly Ash) and IAEA-336 (Lichen) were analyzed. Results obtained with the version 3.12 of the k 0-IAEA program were found to be in good agreement with the data obtained with the established relative method using WINSPAN-2004 software. Detection limits for elemental analysis of geological and biological samples with NIRR-1 facilities are provided.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: J. Moon, M. Ebihara, B. Ni, B. Arporn, P. Setyo, R. Theresia, B. Wee, N. Salim, and P. Pabroa

Since 2000, collaborative studies for applying NAA have been performed through the Forum for Nuclear Cooperation in Asia (FNCA) sponsored by the Japanese Government. White rice is a main food for Asians and thus was selected as a common target sample for a collaborative study in 2008. Seven Asian countries including China, Indonesia, Japan, Korea, Malaysia, Philippines and Thailand, are greatly concerned about the composition of arsenic, heavy metals, and essential trace elements and took part in this study. Rice samples were purchased and prepared by following a protocol that had been proposed for this study. Samples were analyzed by their own NAA systems. In each country, more than 10 elements were examined and the results were compared. These data will be very useful in the monitoring of the levels of food contamination and to evaluate the nutritional status for people living in Asia.

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Abstract  

A neutron-induced prompt -ray analysis (PGA) has become widely utilized due to the improved analytical sensitivities and detection limits especially by using low energy guided neutron beams. Current studies on the low energy neutron guided beam PGA are reviewed. Historical backgrounds, current analysis systems, advantages when compared with conventional NAA, standardization for elemental determination and analytical applications in JAERI of the guided beam PGA are described.

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Abstract  

A study was carried out using NAA to measure the concentration of Al and Fe leached from kitchen ware into some popular Mexican sauces and juices. These elements were measured in red and green hot sauces cooked in Fe, Al and clay pans compared to a stainless steel pan. Similarly Al was measured in organe and grapefruit juices obtained using an Al extractor compared to a plastic one.

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Abstract  

Principles of the expression of uncertainty in measurements are briefly reviewed and special aspects of the uncertainty quantification in NAA are discussed in detail regarding the relative and k 0-standardization in both modes of the technique, i.e., INAA and RNAA. A survey of uncertainty sources is presented and calculation of the combined uncertainty is demonstrated by an example of manganese determination in biological material by RNAA.

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Abstract  

The position of pre-irradiation separations in neutron activation analysis is shortly discussed. Special attention is given to separations for purification and/or concentration of analyte elements, either complexed or uncomplexed, via sorption on activated carbon. It was shown for a number of trace elements that the blank value introduced due to the use of activated carbon is small or mostly even negligible. The NAA determination via pre-separations based on activated carbon is highlighted for selenium, cobalt and iodine.

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Abstract  

Neutron activation analysis (NAA) has been studied to improve the accuracy and sensitivity of the analysis of trace and ultratrace metallic impurities in plastic materials. There are two main problems in the analysis of plastics by NAA. First the contamination during sample preparation, especially sample crushing procedure is very serious for ultratrace analysis. Another problem is the destruction of the sample capsule due to the pressure build-up by the gases formed during neutron irradiation. A simple preparation technique of the sample crushing method using liquid nitrogen and reducing the capsule pressure by a pin hole was developed to solve the above problems. Two different irradiation and seven cooling conditions were also investigated to optimize the experimental conditions. A SRM from NIST (1632b coal) has been used to investigate the accuracy of the analysis. More than thirty elements could be analyzed in the range of sub-ppb to percent. Samples analyzed in this work were polyethylene and polypropylene which were made by different manufacturing procedure, and pigments. Two kinds of plastic products used for food and drug containers were also analyzed. It was found that NAA could be a powerful technique for the analysis of metallic impurities in plastics even though their concentrations were at ultratrace levels.

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Abstract  

An analytical expression has been developed to calculate the neutron self-shielding in a cylindrical sample using the elemental thermal neutron absorption cross sections, σ abs, and the newly-defined epithermal neutron absorption cross-sections, σ abs,ep. The σ abs,ep were measured experimentally for 13 nuclides and calculated from resonance parameters for 76 nuclides. Agreement between the two was good to about 20% in most cases. A spreadsheet program was written to use these nuclear parameters to perform iterative self-shielding corrections of concentrations measured by NAA. In cases with up to 30% self-shielding, the correction factors had uncertainties varying from 2% to 3%.

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Abstract  

Cellulose cylinders and circular filter papers spiked with known amounts of standard element solutions were prepared for studying some aspects of assessing measurement uncertainty of NAA and the elemental distribution measured by micro-PIXE analysis. Results for the cylinders showed strongly non-homogeneous distribution of the elements, both in radial and vertical directions, dominantly caused by osmosis driven transport of added liquid solution from the centre to the edges. Results for the thin cellulose filter paper disks exhibited weaker peaking of the standard element concentrations at the edges in comparison with the thick cylinders.

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