Authors:M. Frontasyeva, F. Grass, V. Nazarov, and E. Steinnes
An intercomparison of data obtained for a moss reference material (Hylocomium splendens) used as biomonitor of atmospheric deposition by different multi-element techniques is presented. In total 43 elements (Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Zr, Ag, Sn, Sb, I, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, Ta, W, Au, Th, U) were determined using inductively coupled plasma-mass spectrometry (ICP-MS), conventional instrumental neutron activation analysis (INAA), epithermal neutron activation analysis (ENAA) and as well as shorttime neutron activation analysis without and with a6LiD-converter. Advantages and drawbacks of each method are discussed. The introduction of moss reference materials for atmospheric multi-element deposition studies involving nuclear analytical techniques is strongly recommended.
A rapid radiochemical procedure for the separation of iodine has been devised, which is characterized by extremely high decontamination
factors so as to give pure128I spectra with biological materials containing large concentrations of interferring elements such as sodium, bromine and chlorine.
The method is based on ignition in oxygen followed by an oxidation-reduction and extraction-stripping cycle involving nitrite,
sulfite and carbon tetrachloride. Results are presented for ten NBS and IAEA reference materials, frequently referred to in
A series of reference materials intended for use as activation or fission monitors for neutron fluence rate measurements has been prepared by the Joint Research Centre of the European Commission. Certification has been carried out by expert European laboratories and distribution of the certified reference materials (CRMs) is through the BCR programme of the Commission. The list (18 CRMs) includes materials to cover the complete energy spectrum, and suitable for different irradiation times. Fission monitors are 238UO2 or 237NpO2 in the form of microspheres. Activation monitors are high purity metals (Ni, Cu, Al, Fe, Nb, Rh, or Ti), certified for interfering trace impurities, or dilute aluminium-based alloys, where aluminium is chosen as a suitable matrix for reducing the neutron self-shielding effect. Newly certified materials are IRMM-530R Al-0.1%Au, replacing the exhausted IRMM-530 material, used as comparator for k0-standardization, and three new Al-Co alloys (0.01-1%Co). Two others, in the process of certification are Al-0.1%Ag and Al-2%Sc for thermal and epithermal fluence rate measurements. Other candidate reference materials currently being certified are two uranium-doped glass intended for dosimetry by the fission-track technique.
Authors:D. Thompson, S. Parry, R. Benzing, J. Williams, and K. Jarvis
The use of paint as a coating for toys intended for sale on the European market is controlled by a European Standard (EN 71-3:
1994-European Standard for the Safety of Toys, Part 3—Migration of Elements). This work is the result of a preliminary study
organised by the European Commission to produce a new paint reference material which can be used to validate the test methods
given in the European Standard. The migration of elements from painted panels and comminuted paint produced by the Laboratory
of the Government Chemist, (U.K.) was studied. Several methods were used in this certification exercise and this work reports
the recults of neutron activation analysis and inductively coupled plasma mass spectrometry to determine the migration of
As, Ba, Cd, Cr, Hg, Pb, Se and Sb into a simulated stomach environment. Replicate extracts obtained from paint samples gave
a precision of within 10% for most elements by both analytical techniques for the paint panels and for the comminuted paint
sample. This preliminary study has shown that the standard method can provide reproducible results for each of the paint materials
studied and indicates that the study should be continued to produce a fully certified paint reference material.
The enhancement factors possible by using reactor pulsing during neutron activation analysis have been shown to exceed 1.0 for half-lives shorter than 42 seconds. Studies published to date have applied the technique to pure elemental standards in order to evaluate the advantage. In addition, its use has been demonstrated for the analysis of several environmental samples. This paper describes experimental work performed in an effort to demonstrate the utilization of the technique on a wide range of real sample materials. The purpose of the investigation was to assess the value of the methodology to the neutron activation analysis program of our laboratory in support of university research. A series of sample matrices including reference materials, fossil fuels, geological specimen, ecologically important materials and animal and plant tissues have been subjected to pulsed neutron irradiation. Resulting gamma emissions were detected from samples after each irradiation. Representative spectral data are presented. Suitability of the technique for trace analysis are discussed.
Instrumental neutron activation analysis (INAA) has been used at the research reactor of the Institute of Nuclear Techniques
for measuring different types of samples for many years. For standardization purposes, the single comparator method has been
applied. Since the theoretical basis of NAA is well understood, the sources of uncertainty can be well estimated, detailed
uncertainty calculations have been recently performed to meet the increasing demands for method validation. INAA was validated
by the analyses of sets of reference materials (RM), selectivity was controlled, accuracy and precision of the method as well
as linearity, detection limits and measuring ranges were determined. Under the conditions of QA/QC, NAA can meet the high
demands of trace element analysis.
The IAEA's Marine Environment Laboratory has been assisting laboratories in Analytical Quality Control Services (AQCS) for the analysis of radionuclides in the marine environment since the early seventies. AQCS through world-wide and regional intercomparison exercises and the provision of reference methods and reference materials (RM) have been recognized as an important component of quality assurance/quality control. A total of 43 intercomparison exercises were organized and 37 RM were produced for marine radioactivity studies. All important marine matrices were covered, e.g., seawater, marine sediments of different chemical compositions, fish, shellfish and seaplants. RM were prepared from samples collected at contaminated sites (e.g., the Irish Sea, the Baltic Sea, the Arabian Sea, Mururoa and Bikini Atolls, etc.) as well as from sites affected only by global fallout (e.g., the Pacific Ocean). Available RM are listed in the IAEA biennial catalogue and can be purchased at a minimal price. An overview of prepared RM for radionuclides in marine matrices is presented and discussed in more detail.
Authors:Ni Bangfa, Peng Lixin, Wang Pingsheng, and Tian Weizhi
Characterizations of three major parameters of Certified Reference Materials (CRMs) concentration values of multielements, homogeneities of multielements, and stabilities of the materials, were further studied by NAA. In the determinations of multielements in RMs, both relative and K0 (and its extension) standardizations were used in an effort to detect hidden systematic errors and expand the number of determinable elements. In the evaluations of multielemental homogeneities, double sampling constants as well as Ingamells' Ks and F-test were used to establish semi-quantitative expressions of sampling uncertainty vs. size and number of subsamples for given elements in given materials. For the investigation of the stabilities of certified values, K0 NAA is to be used in follow-up analyses to test variations of certified values and provide updated and/or newly determined data. The final goal is to make NAA a definitive method for multi-trace element certification, a reliable method for homogeneity characterization, and a reproducible method for stability test. Examples are given to show preliminary results on the above aspects.
A procedure for monostandard INAA of 21 elements (Hg, As, Br, Cr, Sb, Se, Ba, Zn, Ca, Ce, Co, Cs, Eu, Fe, Hf, K, La, Rb, Sc, Sr, Ta) in Chinese Biological Standard Reference Material (peach leaves) is described. The accuracy of the procedure was checked by analyzing the U.S. NBS Standard Reference Materials SRM-1571 and SRM-1632a.