The internal standard method coupled with the standard addition method has been applied to the analysis of environmental materials, such as urban particulate matter, vehicle exhaust particulates and coal fly ash by photon activation. High-resolution gamma-ray spectrometry makes possible to use multi-internal standard gamma-rays, in order to crosscheck the analytical results obtained from each internal standard. It was ascertained that this method can provide not only accurate analytical results but also the information of homogeneity of samples, correlation of elements in the sample, loss or contamination in the preparation process.
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.
As a new method, stable-isotope dilution activation analysis has been developed. When an element consists of at least two
stable isotopes which are converted easily to the radioactive nuclides through nuclear reactions, the total amount of the
element (xg) can be determined by irradiating simultaneously the duplicated sample containing small amounts of either enriched
isotope (y g), and by using the following equation.
Where M and M* are atomic weights of the element to be determined and the enriched isotope used as a spike,θ1 andθ2 are natural abundances of two stable isotopes in the element,θ1*
are isotopic compositions of the above isotopes in the enriched isotope, and R and R* are counting ratios of gamma-rays emitted by two radionuclides produced in the sample and the isotopic mixture. Neither calibration
standard nor correction of irradiation conditions are necessary for this method. Usefulness of the present method was verified
by photon activations of Ca, Zn and Ce using isotopically enriched48ca,68Zn and142Ce.
A new internal standard method for activation analysis has been developed. This method is characterized by that a suitable element present originally in the sample is used as an internal standard and the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample under examination contains Wag of trace element A to be determined together with a known amount of element B which is usable as an internal standard, and when the comparative standard is prepared by adding W
g of accurately known small amount of the element A to the duplicated sample, even if the sample and comparative standard are irradiated separately by particles with different fluxes, Wa can be determined, easily by using the following equation: Wa=W
/AR)-1] Where AR and A
are counting ratios of gamma-rays emitted by two radioactive nuclides produced from the element A and B in the sample and comparative standard, respectively. Neither correction of the inhomogeneities of flux between the sample and comparative standard, nor that of, the self-shielding effects are necessary for the present method. The usefulness of the method was examined through the determination of Co, Ni, Rb and Sr in pepperbush by means of photon activation, and the precision and accuracy of the method were proved to be valid.
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 study effective applications of the photon activation analysis using the internal standard method, determinations of Cr, Co, Ni, Zn, As, Rb, Sr, Y, Zr, Nb, Sb, Cs, Ba, Ce and Pb in two marine sediments as environmental materials have been examined by the use of a personal computer-based gamma-ray spectrometer equipped with a micro-robot for sample changing. In these determinations, some major and minor constituent elements in the samples were properly used as effective internal standards to check the roles with each other. As a result, it was demonstrated that accurate and precise determinations of the above 15 elements were achieved efficiently and favourably.
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 study instrumental charged-particle activation analysis using the internal standard method, simultaneous determination of several selected elements, such as Ca, Ti, V, Fe, Zn, As, Sr, Zr and Mo, in oyster tissue, brewer's yeast and mussel has been examined by using the respective (p, n) reactions and a personal computer-based gamma-ray spectrometer equipped with a micro-robot for sample changing. In the above determination, constant amounts of Y and La were added to the sample and comparative standard as exotic internal standards. As a result, it was demonstrated that concentrations of the above elements can be determined accurately and precisely.
The combined use of photon activation and γ-γ coincidence spectrometry is described for the useful and selective nondestructive
determination of nickel in geological materials. This method is characterized by the utilization of the nuclide emitting β+ particles in its decay and γ-γ coincidence counting with two gates: one for the annihilation photopeak region and the other
for the higher Compton plateau region. The practical detection limits by this method for nickel, arsenic, rubidium, sodium
and scandium in silicate matrices could be set at 2.0, 1.2, 9.0, 110 and 1.4 μg, respectively.
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.