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Abstract  

Nine intercomparisons of the determination of mercury present as impurity in different materials have been organised. 24 laboratories in 10 different countries took part, mainly using activation analysis and atomic absorption techniques. The results show that the reliability of the data produced and reported in this area leaves much to be desired, and that continuous control of the quality of mercury analysis in the extremely low concentration range is essential.

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Abstract  

We have developed a novel advanced enrichment apparatus for environmental tritium analysis called SPET (Solid Polymer Electrolysis for Tritium Water). It generates no explosive gas, requires no aqueous electrolyte, terminates enrichment rapidly, and the volume reduction is infinite. It has an automatic shutdown system which gives uniform conditions on every run, making the handling and determination of tritium concentrations very easy. The reliability of SPET was studied using environmental concentration standard water and the reproducibility error was found to be within 4%, which is sufficient for environmental measurements.

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Abstract  

A method for the rapid evaluation of90Sr in environmental matrices has been developed. It is a one-day time-consuming procedure compared with 20–25 d of the traditional methods. It is based on a partial measurement of the sample activity and on data extrapolation. This work reports the methodology and its reliability.

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Abstract  

A new method for the simultaneous determination of molybdenum and tungsten in biological materials by neutron activation analysis has been developed. It involves a single step radiochemical separation of both elements by extraction chromatography using -benzoinoxime supported on Bio-Beads SM 2. Good accuracy and precision of the method was demonstrated analyzing Bowen's Kale and IAEA's H-8 /Horse Kidney/ reference materials. The method was applied to check the reliability of the results obtained by one standard and one newly developed spectrophotometric methods for the molybdenum content in some plant materials.

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In an attempt to explain how the calibration factor of a heat flux DSC cell depends both on the standard utilized and on the experimental variables, a study has been undertaken of the entire DSC trace.

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Abstract  

Peak search and analysis of the programs often associate peaks found in gamma-ray spectra of the radionuclides that are not present in the sample. Such radionuclides have to be excluded from the reported results. The dilemmas connected with reporting of the results near the detection limit are usually avoided by introducing a reporting limit exceeding considerably the detection limit. This approach has the drawback that small concentrations of emitters may not be reported, even though enough evidence for their presence in the sample is available. In this paper the statistical analysis of causes, which lead to manual elimination of radionuclides from the results of automatic analysis is presented for a set of measurements in our laboratory, covering a period of more than two years. Possibilities to improve the software to automatically detect and eliminate such results are presented as well. From the conclusions additional instructions to the operators on how to evaluate such peaks can be compiled.

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Abstract  

The forensic activation analyst must often evaluate his own results as they relate to certain legal or moral situations, since investigative officers, and courts of law are not usually competent to make judgements of the validity or meaning of scientific data. In providing scientific evidence in court, two criteria for criminal identification must be met: (1) suspect's sample should be similar to sample found at the scene of the crime, (2) samples relared to other people in the same statistical population should not generally match that found at the crime site. When two or more specimens are submitted for comparison by NAA they will usually fall into one of three classes: (a) materials about which we have partial or inconclusive data, (c) materials with an excellent analytical data background. Ideally all cases would fall in category c; in practice, very few. Some examples of cases and/or situations that fall into these three categories in both individual and corporate investigations are given.

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The most decisive phenomena arising either from specific DTA measurements (heat inertia, temperature deviation, self-heating) or from non-isothermal kinetic treatment (overlapping models, characteristics determinations) are discussed.

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Abstract  

The LPTD-MS method, used to determine kinetic parameters in the thermal degradation of polymers by means of volatilization curves, was applied to TG data and the results were compared with those obtained by the methods of Flynn & Wall, Friedman, Freeman & Carroll, and Coast & Redfern.

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