Authors:Zheng Fang, Shaofen Wang, and Zhenghua Zhang
The standard electrode potential of an electrode is a very important electrochemical quantity. Usually, it is obtained by the extrapolating the electrode potentials of extremely dilute solution along the line
Authors:R. Filby, G. Van Berkel, A. Bragg, A. Joubert, W. Robison, and C. Grimm
National Bureau of Standards residual fuel oil Standard Reference Materials, SRM 1619, 1620a, 1634a, and former SRM 1634 were analyzed for 20 trace elements by instrumental neutron activation analysis to determine whether these materials are suitable trace element standards for elements other than the 6 elements certified in SRM 1634a. The SRM 1634a is a suitable standard for Ni, V, Se, Na, Zn, As, Cr, Fe, Ce, Sm and La but Co, Ba, Nd, Cs, Eu, Sc, and Sb appear to be heterogeneously distributed and are probably present in mineral particulates. The SRM 1619 is a convenient standard for V and for low Ni content oils, but SRM 1620a does not appear to be a suitable standard for any trace element investigated.
Authors:A. Ahmad, P. Gray, T. MacMahon, and M. Macwani
To carry out neutron activation analysis without using multielement standards requires knowledge of (i) the absolute photopeak
efficiency as a function of energy of the gamma-ray detector, (ii) nuclear data for each reaction used, and (iii) neutron
flux parameters for the irradiation position. The present paper discusses each of these topics and shows an example of the
determination of flux parameters and improved nuclear data.
Authors:M. Hadžišehović, I. Močilnik, A. Milojević, K. Buraei, and S. Pongrac
For the determination of a tritium absolute activity standard, a method of internal gas counting has been used. The procedure
involves water reduction by uranium and zinc and measurement of the absolute disintegration rate of tritium per unit of the
effective volume of the counter by a compensation method. A brief description of the measuring apparatus is given, as well
as a critical discussion of the brass counter quality and the possibility of obtaining equal working conditions at the counter
One of the most crucial points of citation-based assessments is to find proper reference standards to which the otherwise meaningless plain citation counts can be compared. Using such standards, mere absolute numbers can be turned into relative indicators, suitable for cross-national and cross-field comparisons. In the present study, three possible choice of reference standards for citation assessments are discussed. Citation rates of publications under study can be compared to the average citation rates of the papers of the publishing journals to result inRelative Citation Rate (RCR), an indicator successfully used in several comparative scientometric analyses (see, e.g. Refs 1–5). A more customized reference set is defined by therelated records in the new CD Edition of theScience Citation Index database. Using the socalled bibliographic coupling technique, a set of papers with a high measure of similarity in their list of references is assigned to every single paper of the database. Beside of being an excellent retrieval tool, related records provide a suitable reference set to assess the relative standing of a given set of papers as measured by citation indicators. The third choice introduced in this study is specifically designed for assessing journals. For this purpose, the set of journals cited by the journal in question seems to be a useful basis to compare with. The pros and cons of the three choices are discussed and several examples are given.
In torsional braid analysis (TBA) the thermocouple junction is not in contact with the specimen, and therefore temperature standards are necessary. However TBA is devised only for application to high polymers, which are not appropriate for standards. The transition and fusion temperatures of several substances of low molecular weight, such as water,o-terphenyl, potassium nitrate andn-azoxyanisole, have been studied by TBA, and their applicability as standards to TBA is discussed. It is found that water,o-terphenyl and potassium nitrate can be used as standards.
Authors:R. Zaghloul, E. Gantner, M. Mostafa, and H. Ache
A physical approach is described for instrumental multielement activation analysis with whole neutron spectrum (without Cd-cover) using the monostandard (single comparator) method. To test the capabiliteries of this method, 15 samples representing different Egyptian granite rocks were analyzed. As many as 21 trace elements beside Fe, K and Na were determined. Calculation of the experimental data has been done using the Gamma-Monostandard Analysis program with the Commodore Computer available at the Institute of Radiochemistry at Garching near München. The accuracy of the method for nondestructive multielement analysis agrees within 3% with the relative method using multielement standards.
Standard reference materials, normally used to check accuracy and precision of analytical methods or for interlaboratory comparisons,
are proposed for use as multielement irradiation standards in neutron activation analysis (NAA). The advantages are simplicity
of operation, and elimination of errors inherent in the preparation of a large number of synthetic standards at the trace
element level. Examples of the approach are illustrated in the analysis of geological materials, soils, sediments, meteorites,
lunar samples, coal and fly ash using the USGS diabase W-1 as the irradiation standard. Plant materials and animal tissue
are analyzed using NBS Orchard Leaves as the irradiation standard. Best values for four popular SRM's (W-1, Bowen's Kale,
Orchard Leaves, and Bovine Liver) are tabulated to facilitate further use of the proposed approach to multielement neutron
The National Bureau of Standards has, for the past five years, been developing natural-matrix, environmental-level radioactivity Standard Reference Materials in large quantities to be available to users over a ten year time period. These materials have been found to be useful for the evaluation of radiochemical methods and analysis, as interlaboratory comparison materials, and as quality assurance materials. To date, six Standard Reference Materials have been issued: River Sediment, Human Lung, Human Liver, Rocky Flats Soil-1, Freshwater Lake Sediment, and Peruvian Soil. The concentrations of twenty radionuclides have been certified in these materials.