In order to achieve the highly accurate and precise multielement determination in environmental materials, the usefulness of the comparative standard provided by the processing method proposed previously for soil samples has been re-examined using calcareous loam soil, light sandy soil and river sediment as unknown samples. As a result, it was also demonstrated that concentrations of 15 trace elements in each sample can be determined effectively and reasonably.
Determination of phosphorus in low-alloy steels by alpha-particle activation analysis has been studied in detail. After thick target yield curves of main interferences produced from the sample were measured as a function of alpha energy, the working standard for the present experiments was provided by applying the internal standard method coupled with the standard addition method under the most suitable bombarding conditions. Using the above working standard, it was demonstrated that the concentration of phosphorus in several low-alloy steels can be determined accurately and precisely by ordinary alphaparticle activation analysis.
In order to examine effective applications of the newly developed internal standard method, determinations of Cr, Co, Ni, Zn, As, Rb, Sr, Y, Zr, Nb, Cs, Ce and Pb in three environmental materials, such as pond, lake and estuarine sediments, have been tried by means of photon activation. In these examinations, some major constituent elements in the above sediments were properly used as excellent and effective internal standards. In consequence, it was confirmed that highly accurate and precise determinations of the above 13 elements were achieved easily and favourably.
A thermal resistive window flow counter available for hard beta-emitters in radio gaschromatography effluents was developed.
The plateau region of the counter showed more than 150 volts long even if the counter was operated at temperature up to 200°C.
The radio gas-chromatograms for real samples containing high boiling compounds showed high resolution and shapper peaks.
Charged particle activation analysis of phosphorus in biological materials using the31P (α,n)34mCl reaction has been studied. Since34mCl is also produced by the32S (α,pn) and the35Cl (α, α′ n) reactions, the thick-target yield curves on phosphorus, sulfur and chlorine were determined in order to choose
the optimum irradiation conditions. As a result, it was found that the activation analysis for phosphorus without interferences
from surfur and chlorine is possible by bombarding with less than 17 MeV alphas. The applicability of this method to biological
samples was then examined by irradiating several standard reference materals. It was confirmed that phosphorus can readily
be determined at the detection limit of 1 μg free from interferences due to the matrix elements.
A method has been developed where the element to be determined in the sample consists of at least two stable isotopes, which are easily converted to radionuclides through particular nuclear reactions. The sample is previously processed by adding a known quantity of an enriched isotope of the element, while the comparative reference is prepared by taking an arbitrary amount of the natural element under investigation. The usefulness of the method was verified by photon activation analysis of strontium in standard reference materials of tomato and citrus leaves, using isotopically enriched86Sr as a spike, and the accurary and precision of the method were proved to be valid.
In order to apply the stable-isotope dilution method to charged-particle activation analysis, determination of strontium in biological materials has been studied by proton activation using isotopically enriched86Sr as a spike. To avoid thermal decomposition of biological materials due to the low penetrating power of proton beam, and to eliminate interfering nuclear reactions due to the matrix elements, strontium in the sample and/or isotopic mixture as a comparator was separated chemically together with most of calcium before bombardment, and the fraction isolated was converted to a silica-gel pellet as a most suitable physical and chemical form for bombardment. By processing as above, it was demonstrated that the strontium contents in the biological materials can be determined accurately, precisely and easily. Through a series of experiments, the method was also proved to be applicable for charged-particle activation analysis.
A new internal reference method for activation analysis has been developed. The method can be used effectively for special samples in which suitable elements as internal standards are absent and the self-shielding effect can be neglected. In this method, Wb g of element B as an internal reference is added to the sample which contains Wa g of element A to be determined, whereas the comparative standard is prepared by mixing only the element A and B in a known concentration ratio of W
/Wb. When the sample and comparative standard are irradiated by particles with the same energy distribution, even though both are irradiated separately by particles with different flux, Wa can be determined easily by the following equation.
where Ag and AR are count ratios between gamma-rays emitted by two radioactive nuclides produced from elements A and B in the sample and comparative standard, respectively. The usefulness of the present method was examined through the determination of Ti, Cr, Ni and Zr in several commercial aluminium alloys by means of photon activation, and the accuracy and precision of the method were verified.
Multielement determinations in the certified reference materials of soils (IAEA soil-5 and 7) have been studied fundamentally by instrumental photon activation analysis using the internal standard method coupled with the standard addition method. For the soil-5 sample, in the first place, the qualities of the comparative standards prepared by two processing methods were compared with each other. As a result, it was demonstrated that a highly accurate and precise multielement determination can be achieved easily by minor improvement in the processing method of the comparative standard to ensure homogeneity. The utility of this processing method for soil samples was proved further through a similar analysis in another soil sample (IAEA soil-7).
In order to demonstrate the usefulness of alpha-particle activation analysis, simultaneous determination of P, Cl, K and Ca in commercially available control serums has been studied fundamentally. After thick target yield curves of radionuclides produced from the element to be determined were measured as a function of alpha energy together with those of the interferences, an optimum working standard for the present experiments was provided by applying the internal standard method to a human serum under the most suitable bombardment conditions. Then, the concentrations of the above four elements in several control serums were determined efficiently and reasonably by ordinary alpha-particle activation analysis.