Reference materials are necessary to improve or to maintain a high quality of analysis. To avoid bias as far as possible, the BCR certifies reference materials on the basis of results of different methods used by different laboratories. A proper selection of good methods and laboratories makes it possible to obtain excellent agreement and narrow confidence intervals. Neutron activation techniques are suited for many key elements; their results are in good agreement with those of other techniques.
Authors:M. Bacchi, E. Fernandes, E. França, and P. Bode
This work is focused at the demonstration of the overall adequacy of the procedures introduced in a Brazilian laboratory for conducting the k0-standardized NAA. Concentrations of 29 elements determined in certified reference materials of plants and geological matrices are evaluated. Most of the experimentally determined values agreed well with the reference data and no consistent bias could be attributed to the analytical system adopted.
Instrumental neutron activation analysis (INAA) was applied to determine Ca, Cl, Mg, Mn, Na, Sr and Zn in dentine and enamel
tissues from human permanent and deciduous teeth. Comparisons were made between the results obtained in these different dental
tissues as well as those obtained in permanent and deciduous teeth. The findings obtained were also compared with the published
data. The accuracy and the precision of the results were evaluated by analyzing certified reference material.
Authors:E. Shabana, K. Al-Hussan, and Q. Al-Jaseem
A relatively simple and rapid radioanalytical method, limited to milk, is adapted for investigating soil, biological and water samples for90Sr. The method is based on a selective separation and successive counting of equilibrium quantities of its daughter 90Y, which can be extracted by tributyl phosphate from nitrate medium and stripped by conc. ammonia solution. 90Y is separated from possible iron and measured by Cerenkov counting. The procedure is thoroughly tested with certified reference materials and used lately for determining90Sr in some environmental samples in the Riyadh region. The results obtained are given and discussed.
Authors:O. Rizo, E. Herrera Peraza, M. Manso Guevara, I. Pellón, M. López Reyes, M. Cabrera, and M. Montero Cabrera
The main results obtained during the characterization of the Triga Mark III reactor at NNRI, Salazar, Mexico, the development
of the nonconventional multimonitor HAV-1, the use of Certified Reference Material (CRM) as multimonitor fork0-factors experimental determination, and to study the reactor power and slowing-down thickness dependencies of the reactor
flux parameters and its influence ink0-INAA are presented. The experience of thek0-INAA group at ISCTN, in the application of this analytical technique for different purposes is resumed.
Authors:P. Lam Ramos, D. Frías Fonseca, M. González Garcia, D. Aguiar Lambert, J. Estévez Alvarez, I. Pupo González, and D. López Sánchez
The objective of the present study was the elaboration of a procedure for the determination of Y, La, Ce, Pr and Nd in soils by spectrophotometry with Arsenazo III preceded by a separation-concentration stage, which includes coprecipitation and ion exchange. Multielement analysis by energy dispersive X-ray fluorescence (including Y, La, Ce and Nd) and flame atomic absorption spectrophotometry was carried out simultaneously in order to obtain a general characterization of the soil samples. Certified reference materials and statistical intercomparison of the obtained results were used to evaluate the accuracy of the methods. The precision was examined by analyzing replicate samples.
Authors:Xiongxin Dai, Zhifang Chai, Xueying Mao, and Hong Ouyang
The Ir, Au and Pd concentrations in three certified reference materials SARM-7, FC-1 and DZ-1 were determined by neutron activation analysis using -amino pyridine preconcentration. Good agreement between the reference values and our results was obtained, and the reliability of our method was confirmed. This method is suitable for ppb or sub-ppb levels of Ir and Au analyses in environmental and geological samples. The Ir and Au levels in a Chinese coastal sediment GBW07314 were also analyzed.
Concentration levels of eight trace elements in 120 samples of human blood serum were investigated by Instrumental Neutron Activation Analysis (INAA) for the purpose of medical research. The elements Co, Cr, Cs, Fe, Rb, Sc, Se, and Zn were simultaneously determined by the relative method in comparison with inorganic standards treated under identical conditions. The process of analysis and its reliability was checked using human serum and IAEA certified reference material. Statistical results are expressed in ppm or ppb. Both normal and, if necessary, log-normal frequency distributions of all elements determined are presented, types of distribution curves are verified statistically on 95% level of probability.
The selenium content of a variety of food items representing a normal hospital diet has been determined by cyclic instrumental neutron activation analysis (CINAA) through the 162-keV gamma-ray of the77mSe nuclide. The CINAA method is very simple and rapid. It involves irradiation of a sample for 20 s, decay for 20 s, and counting for 20 s. The precision of the method has been significantly improved by recycling the samples up to 4 times. The accuracy has been evaluated by analyzing a number of certified reference materials of varied selenium levels.
The comparability of analytical results from different laboratories requires accurately known concentrations in the applied standards. Dilution effects of different multielement synthetic standard solutions have been studied by measuring 10–12 different concentrations of the same solution. Peak area comparison of four Certified Reference Materials (CRM's) using one value for the evaluation of the other three repetitively led to the intercomparison (degree of compatibility) of the certified values. The idea of the preparation of each laboratory's secondary reference standard by comparison of synthetic multielement standards with as many CRM's as practically feasible is advocated to improve the reliability of analytical results.