The publication of ANSI Standard N42.22-1995, “Traceability of Radioactivity Sources to the National Institutes of Standards
and Technology and Associated Instrument Quality Control”1 provides an unambiguous method for establishing the traceability of radioactivity sources to NIST. The criteria necessary
for manufactures to achieve traceability are provided in the following areas: quality assurance, facilities and equipment,
participation in a NIST measurements assurance program, and certification of sources.
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.
Authors:Silke Dubbert, Birgit Klinkert, Michael Schimiczek, Trudy M. Wassenaar, and Rudolf von Bünau
various E. coli strains have been demonstrated in a number of murine models, which are summarized elsewhere, but all have their limitations [ 22 ]. Since rats are more easily colonized by E. coli than mice, and since rats are the standard test animal
The (U. S.) National Bureau of Standards standard reference material 1633a (coal flyash) was standardized for the concentrations of 29 elements against chemical standards by instrumental neutron activation analysis. United States Geological Survey basalt standard BCR-1 was analyzed concurrently as a check. SRM 1633a is a good multielement comparator standard for geochemical analysis for 25 of the elements analyzed and is a better standard than rock-powder SRMs commonly used. Analytical data for USGS DTS-1, PCC-1, GSP-1, BIR-1, DNC-1, and W-2; NBS SRMs 278 and 688; and GIT-IWG (French) anorthosite AN-G are also presented.
The control of analytical data by randomly inserted standards or reference materials is quantified in terms of elementary statistics. The consequences of a given number of standard aliquots are interpreted on the basis of the a priori expectation on the average defective fraction. It appears that, in most cases, standards serve to detect sudden large errors only. Some practical examples are considered.
Authors:K. Masumoto, M. Hara, D. Hasegawa, E. Iino, and M. Yagi
The internal standard method coupled with the standard addition method has been applied to photon activation analysis and proton activation analysis of minor elements and trace impurities in various types of iron and steel samples issued by the Iron and Steel Institute of Japan (ISIJ). Samples and standard addition samples were once dissolved to mix homogeneously, an internal standard and elements to be determined and solidified as a silica-gel to make a similar matrix composition and geometry. Cerium and yttrium were used as an internal standard in photon and proton activation, respectively. In photon activation, 20 MeV electron beam was used for bremsstrahlung irradiation to reduce matrix activity and nuclear interference reactions, and the results were compared with those of 30 MeV irradiation. In proton activation, iron was removed by the MIBK extraction method after dissolving samples to reduce the radioactivity of56Co from iron via56Fe(p,n)56Co reaction. The results of proton and photon activation analysis were in good agreement with the standard values of ISIJ.
Errors in preparing standards, especially multielemental standards, are extremely important if accurate results are desired from neutron activation analysis (NAA). It is often convenient to prepare standards for NAA from single or multi-element solutions which are then deposited onto (or into) a suitable matrix, such as filter paper or quartz vials. There are many potential sources of error in preparing single-element standards including: impurities and non-stoichiometric composition of the element or compound used to prepare the standard solutions; evaporative losses of solvent; inaccuracy of calibration, and imprecision of the pipettes used; moisture content of elements or compounds used; contamination from reagents, equipment, laboratory environment, or final matrix of the standard; instability of standard solutions (i.e., to losses via precipitation or adsorption), and losses of volatile elements during dissolution and/or irradiation. Additional sources of error in preparing multielement standards includes: instability of mixed, multielement solutions, and cross-contamination of one element by the addition of a second element. Procedures previously used by the author at NIST to prepare multielement standards with concentrations accurate to about one percent are described. Additional techniques needed to prepare multielement standards with accuracies better than 1 percent will be discussed.