Results of several IAEA intercomparison runs organized over the last 8 years are analyzed from the point of view of contribution
and performance of NAA as compared to other techniques. It is shown that NAA is the method of good accuracy and precision
providing on average greater share of results than any other single analytical technique. The prominent position of NAA among
other methods used in trace analyses seems to be firmly established and there are no signs that there might be any change
of the trend in the nearest future.
It is shown that, depending on the ion exchange system and experimental conditions, the plate height can either increase or
decrease with flow rate. The results are interpreted using the modified Glueckauf equation containing an additional term which
allows for longitudinal diffusion in the resin phase. A new method for estimating the diffusion coefficients in the resin
phase is suggested. Different susceptibility of various chromatographic systems to loading effects is demonstrated and discussed.
Other factors influencing the degree of separation like particle size, magnitude of distribution coefficients, temperature
and resin cross-linking are briefly mentioned.
Recently developed radiochemical separation scheme for the simultaneous detemination of trace amounts of molybdenum and uranium in biological materials by NAA has been further refined and used for the detemination of these elements in several certified reference materials. The method assures very selective and quantitative separation of the indicator radionuclides:99Mo-99mTc and239Np from practically all accompanying activities followed by almost interference-free measurement by gamma ray spectrometry. The method can be applied to materials of both animal and plant origin and enables correcting the molybdenum results for uranium fission interference reaction thus assuring good accuracy for both elements down to ppb levels. The detection limits amount to 2.5 ppb (Mo) and 0.15 ppb (U) for ca. 200 mg samples.
A new, very accurate (definitive) method for the determination of trace amounts of cobalt in biological materials has been devised. The method is based on combination of neutron irradiation with quantitative and selective post-irradiation separation of cobalt from all accompanying radionuclides followed by measurement by -ray spectrometry. Column chromatography in which owing to addition of Co carrier the course of separation can be followed visually is the key element of the separation scheme. Several criteria have been formulated which must be simultaneously fulfilled in order to acknowledge the result as obtained by a definitive method. The high accuracy of the method has been demonstrated by the analysis of several certified reference materials of widely different Co contents.
On a mis au point une méthode d'analyse par activation neutronique du lanthane et de l'or en quantités inférieures au ppm
dans l'acier, sans détermination du rendement chimique. La méthode consiste à isoler quantitativement les activités de La
et d' Au par des procédés d'échange d'ions et à faire ensuite une spectrométrie NaI(T1). La limite de détection est abaissée
jusqu'à 10 et 5 ppb pour La et Au respectivement. Il n'y a pratiquement pas d'interférence avec les autres éléments habituellement
présent dans l'acier.
A method for the determination of cadmium and zinc in geological and environmental materials by radiochemical neutron activation analysis is presented. It is based on the isolation of the analytes using the amphoteric ion exchange resin Retardion 11A8. The elaborated ion exchange procedure is accomplished both before and after neutron activation. Depending on the eluent composition Retardion 11A8 acts as an anion or a cation exchanger. The method was tested by determining Cd and Zn in two reference materials: Lake Sediment (SL-1) and Zinnwaldite ZW-C. The results of quantitative determinations show good agreement with the certified values.
A new universal radiochemical separation scheme for selective and quantitative isolation of molybdenum and neptunium (formed from uranium), from neutron irradiated biological materials has been elaborated. The procedure is based on ion exchange and extraction chromatography with final fixation of molybdenum on a column with -benzoinoxime supported on Bio-Beads SM2 and neptunium on Dowex 1-X8 [No
]. The separated elements are quantified using gamma-spectrometric measurements. The new NAA method is able to overcome problems associated with high contents of phosphorous in some samples and assures detection limits better than 3 ppb for both elements. The validity of the proposed scheme has been demonstrated by the analysis of several CRM's.
A new method for the selective radiochemical separation of cadmium from other elements, present in biological materials, using amphoteric ion exchange resin Retardion 11A8 has been elaborated. Cadmium can be taken up by the resin either as anionic chloride complexes or cationic ammine complexes, depending on the composition of the eluent, exploiting both cation and anion exchange functions of the ion exchanger. The conditions in which Cd is quantitatively retained and eluted from Retardion 11A8 were established. The method of selective isolation of cadmium was further used for the determination of Cd in three biological certified reference materials by neutron activation analysis. Analytical results obtained with the use of the proposed separation procedure show good agreement with the certified values.
Distribution coefficients of Pt, Ir, Pd and Rh in the systems Dowex 1 [Br−]−HBr plus 0.0035M bromine and Dowex 1 [Br−]−HBr plus 2% N2H4·HCl, were determined with the aid of radioactive tracers by batch equilibration for the resins of nominal cross-linking 2,
4 and 8, respectively. Column experiments showed that Dowex 1X4 should be used for separations because of the favourable dynamics
of the column process. Elution conditions for the quantitative separation of both trace and milligram amounts of Ir−Pt, Rh−Pt,
Pd−Pt and Ir−Pd−Pt mixtures are given. Some data on the effect of temperature upon the quality of separation are also presented.