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Abstract  

Analyses for value assignment in the renewal Standard Reference Materials® SRM 1598a Animal Serum and SRM 1577c Bovine Liver included extensive characterization by neutron activation analysis (NAA). Conventional instrumental NAA procedures were complemented by pre-irradiation chemical separations for the determination of Al, V, Mn, and Cu, radiochemical separations for the determination of Ag, As, Cd, Cr, Cu, Mo, Sb, and Se, and the use of (anti-) coincidence gamma-ray spectrometry systems for the instrumental determination of Ag, Cr, and Hg. The previous materials, SRMs 1598, 1577, and 1577b, were analyzed together with the new materials for quality control.

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Abstract  

Recycling steel products demands a new technique for determining tramp elements in steel. Tramp elements, As and Sb, in some iron certified reference materials were determined by neutron activation analysis with multiple gamma-ray detection method and reported in MTAA11. In MTAA12, the authors reported the lower limit of determination values (LDL) and the dispersion of this method. The values of the LDLs for As and Sb in high purity iron were 0.002 and 0.0009 μg·g−1. The dispersion is small enough to satisfy the demand from materials science.

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Abstract  

Loess sediment was prepared and characterized with well-established K, Th and U contents, and corresponding 40K, 232Th and 235,238U activities, intended for use as a reference material in the annual radiation dose determination for luminescence dating. To this purpose, loess was collected in Volkegem, Belgium, and — after drying, pulverizing and homogenizing — characterized via k 0-INAA and HPGe gamma-ray spectrometry. This led to 12 kg material with a grain size below 50 μm, with established K, Th and U homogeneity, with the 232Th and 238U decay series proven to be in equilibrium, and with the following K, Th and U reference data: K = 16.5±1.5 g·kg−1 (40K = 497±45 Bq·kg−1); Th = 10.4±0.6 mg·kg−1 (232Th = 42.2±2.5 Bq·kg−1); U = 2.79±0.12 mg·kg−1 (238U = 34.5±1.5 Bq·kg−1; 235U = 1.59±0.09 Bq·kg−1; 235+238U = 36.1±1.7 Bq·kg−1). These data were confirmed via comparison with the results from NaI(Tl) field gamma-ray spectrometry, thick-source ZnS alpha-counting and thick-source GM beta-counting (after converting all data to Gy·ka−1). The reference material is available (as aliquots up to 200 g) from the Ghent Luminescence Laboratory to all interested luminescence dating laboratories upon motivated request.

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Two sets of calibration standards for134Cs and137Cs were prepared by small serial dilution of a natural matrix standard reference material, IAEA-154 whey powder. The first set was intended to screen imported milk powders which were suspected to be contaminated with134Cs and137Cs. Therefore the concentration range of the calibration standards were about 40–400 Bq/kg. The precision of the preparation of the standard with about 7 Bq/kg of134Cs and 39 Bq/kg of137Cs at measurement time was 7.4% and 3.2%, respectively. The preparation of a similar standard by spiking the matrix with radioisotope solutions resulted in a poorer precision, about double that of the former technique. The other set of calibration standards was prepared to measure the environmental levels of137Cs in commercial Venezuelan milk powders. Their concentration ranged from 3–10 Bq/kg of137Cs. The accuracy of these calibration curves was checked by using IAEA-152 and A-14 milk powders. Their measured values were in good agreement with their certified values. Finally, it is shown that these preparation techniques by serial dilution of a standard reference material were simple, rapid, precise, accurate and cost-effective.

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Abstract  

A new biological reference material, which is representative of diets consumed in Finland, has been characterized by means of an intercomparison exercise conducted by the IAEA in the second half of 1985 and in 1986. Results for 35 elements received from 79 participants in 33 countries have been evaluated. A certificate of analysis has been issued with provisional certified values for 22 elements and information values for 2 elements. Neutron activation analysis (NAA) provided approximately one third of all the results reported. Instrumental NAA was used approximately 5 times as frequently as radiochemical NAA. Overall, NAA played an important role in providing useful data for the following 20 elements: Al, As, Br, Cl, Co, Cr, Cs, F, Fe, Hg, I, K, Mn, Mo, Na, Rb, Sb, Sc, Se and Zn. In comparison with the main competing non-nuclear method (usually atomic absorption spectrometry), NAA showed a larger dispersion of results for Cd, Cu, K, and Mg, and a smaller degree of dispersion for Co, Cr, Hg, and Se.

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The feasibility of the use of potassium nitrate and potassium perchlorate as temperature standards in Differential scanning calorimetry has been studied. The solid-state phase transition temperatures of KNO3 and KClO4 were determined by means of DSC. The metrological properties of these salts as calibration materials were examined. The reliability of KNO3 and KClO4 calibrations was investigated by twofold determination of the bismuth melting temperature after the apparatus had been calibrated with indium and lead, and with KNO3 and KClO4. Conclusions were drawn concerning the suitability of these salts for use as DSC temperature calibrants.

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Abstract  

The Laboratory of the Government Chemist (LGC) is a focal point for the production, analysis and certification of reference materials. Within the field of thermal analysis the LGC is concerned with the development of purity standards and materials certified for enthalpy of fusion and melting point. For some time the LGC has been concerned with the significant differences in purity data which can be produced by the different manufactures' differential scanning calorimeters. This paper will highlight the initiatives the LGC is undertaking in overcoming this uncertainty in purity measurements through the use of certified thermal standards.

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Performance of three commercial gamma-ray spectrometric systems was evaluated for precision and accuracy prior to use in characterization of reference materials. Two of the systems were based on fast processing of the analogue signal from the amplifier (EGG Ortec model 672) using a loss free counting module (Canberra model LFC 599) interfaced to one of two analog-to-digital converters (Canberra models 8713 or 8715). The third system was based on a digital signal processor (Canberra model DSP 9660). Performance of the systems was tested over a range of count rates up to a maximum of 70,000 counts per second (dead time up to 90%) using 60Co and 137Cs sources. Best resolution was achieved with an analogue system with ADC 8713. The analytical results obtained with the digital system show the lowest and well-quantified uncertainty.

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Abstract  

We report instrumental neutron activation analysis results for 15 elements (K, Fe, Sc, Cr, Co, Zn, As, Rb, Sb, Cs, Ba, Hf, Ta, Th, and U) in 16 geochemical reference samples, namely SDC-1, SCo-1, SGR-1, STM-1, RGM-1, BIR-1, MAG-1 and BHVO-1 from USGS (United States Geological Survey, Reston), Soil-5, Soil-7 and SL-1 from IAEA (International Atomic Energy Agency, Vienna), and GSS-1, GSS-4, GSS-7, GSR-2 and GSR-3 from IGGE Institute of Geophysical and Geochemical Prospecting, People's Republic of China), The results are compared with literature values. In general our results agree well with recommended or proposed values.

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