Chemical Separation Scheme Research Articles

Distribution patterns of rare-earth elements in biological materials evaluated by radiochemical neutron activation analysis

This study deals with the quantitative determination of eight REE's viz, La, Ce, Nd, Sm, Eu, Tb, Yb, and Lu as an Integral part of a post-irradiation chemical separation scheme for the determination of 14 trace elements in biological materials. REE values are given for NBS Orchard Leaves SRM 1571, NBS Bovine Liver SRM 1577 and Bowen's Kale, as well as for some other biological (reference) materials of plant, animal and human origin.

Extended automated separation techniques in destructive neutron activation analysis; application to various biological materials, including human tissues and blood

An automated post-irradiation chemical separation scheme for the analysis of 14 trace elements in biological materials is described. The procedure consists of a destruction with sulfuric acid and hydrogen peroxide, a distillation of the volatile elements with hydrobromic acid and chromatography of both distillate and residue over Dowex 2X8 anion exchanger columns. Accuracy, precision and sensitivity are tested with reference materials (BOWEN’s kale, NBS bovine liver, IAEA materials dried animal whole blood, wheat flour, dried potatoes, powdered milk, oyster homogenate) and on a sample of pooled human blood. Blank values due to trace elements in the quartz irradiation vials are also discussed.

Determination of Cosmic-Ray-Produced Titanium and. Vahadium in Iron Meteorites.

The concentration of cosmic-ray-produced stable nuclides of titanium and vanadium in iron meteorites, especially in the Grant meteorite, were determined by a surface ionization solid source mass spectrometer using an electron multiplier. A triple filament technique was applied for both elements. A rhenium ribbon was applied to the center(ionizing)filament and for titanium two tantalum ribbons and for vanadium tungsten ribbons to the side(sample)filaments respectively. Repeated experiments using 0.1-1 microgram quantity of reagent titanium and vanadium indicated a satisfactorily high reproducibility throughout the cource of this work. The results with the reagent titanium and vanadium were in a good agreement with the determinations by Hogg and by White et al respectively. Using about one gram of the iron meteorites specimen, the extractions of titanium and vanadium were performed simultaneously in a systematic wet chemical separation scheme with potassium, calcium, chromium, and manganese. For the determination of the absolute contents of cosmogenic nuclides, isotopic dilution analysis was made using enriched 46Ti for titanium and reagent vanadium for vanadium as the spikes. The determination of above nuclides were possible with sufficiently low contamination of natural elements at the levels of 0.1 ppm for titanium and 0.01 ppm for vanadium. The enrichment in 49Ti was observed most prominently in the mass spectrum of titanium samples separated from the iron meteorites. At the same time the other products, 47Ti and 46Ti were also determined with a high reproducibility. 50Ti was also measurable though the error, ±30%, was still high. Examples of the data of cosmic ray produced stable titanium and vanadium are as follows;[unit:×1013 atoms/g. of meteorite]Aroos: 46Ti 4.00, 47Ti 4.85, 49Ti 7.70, 50Ti 0.27, and 50V 5.45. We have completed a set of data at A=50which includes new data of 50Ti and 50V, and our previous data of 50Cr and also 50V.The distribution of these three isobars provides useful measure in the spallation systematics in meteorites. Two parameters, R and S, in the semi-empirical equation of spallation cross section, Inσ(Z)=-R(Z-SA)2+K, were calculated to be 1.5±0.2 and 0.469±0.001 respectively. The radiation age of Aroos was estimated applying widely ranged pairs of both radioactive and stable nuclides, which were now all available. Each age derived from different isobaric pairs agreed well and this may suggest the negligible effect of space erosion or similar mechanisms such as many small collisions in space. In Grant, the depth effect was found to be effectively negligible with 49Ti and 50V in contrast to lighter nuclides such as Ne and K. Any irregurality in a curve of spallation yield vs.ΔA was not observed in mass range of 46-49. The experimental procedure is described in detail.

Determination of Cosmic-Ray-Produced Potassium and Calcium in Iron Meteorites.

A Long lived radio-nuclide 40K and stable nuclides of calcium produced by cosmic ray in iron meteorites were determined by mass spectrometry using surface ionization technique with an electron multiplier. These nuclides were extracted simultaneously in a systematic wet chemical separation scheme with other stable nuclides of titanium, vanadium and chromium and long lived nuclide 53Mn. For the determination of absolute contents of the products, the dilution method was apllied using spikes, 39K and 42Ca. The contamination level of natural potassium and calcium was reduced as low as possible; the lowest, we obtained, was 0.2ppm potassium and 0.4ppm calcium. In such sample, the enrichment of 42Ca, 43Ca, 44Ca and 46Ca due to cosmic-ray products were observed at 70, 200, 20 and 200% respectively. It was not always possible to reach such low contamination level. On the other hand, the most of 40K extracted from iron meteorites was found to be the cosmic-ray products even at a higher contamination level. For the isotope fractionation and the isotope discrimination problem, long lived 40K seems not to be affected seriously because of the very high ratio of cosmic-ray product to natural 40K and of being placed between two stable nuclides of potassium. When we got the lowest contamination, cosmic-ray-produced 41K should be detected at the about 5% enrichment in mass 41 peak. However, we have no mean to correct the isotope fractionation and discrimination of potassium and could not determine the 41K in this work. According to the spallation systematics and also our earlier works, fortunately, 40Ca and 48Ca are produced by negligible amounts by cosmic-ray irradiation. The isotope fractionation and discrimination in the mass spectrometry were corrected by normalizing 40Ca and 48Ca peaks in samples to their reference values which were selected from literatures and our data of reagent calcium. When sample size was very small, mass 42 and 43 peaks were usually disturbed by tenacious hydrocarbon peaks. In order to eliminate such disturbances, the cavity of ion source in mass spectrometer and the filament had to be baked before the measurement in each run. Examples of results are as follows[unit: 1013atom/g of meteorite]. 40K: Grant A-350, 0.526, Grant Q-260. 0.541, Grant E-240, 0.470, Grant I-110, 0.42, Grant I-55, 0.458, Aroos, 0.715, Treysa, 0.546. 43Ca: Grant A-350, 1.77, Grant Q-260, 1.6, Grant I-110, 1.6, Grant I-55, 1.42, Aroos, 2.29, Treysa, 1.55. A dependency on the depth in the meteorite Grant was found to be about 20%, smoothly decreased from the surface to the center for both 40K and calcium. Our samples were not enough in number to determine the preatomospheric size of the meteorite yet. A fine structure in a cumulative spallation yield curve was examined in the isotopic ratios of cosmic-ray-produced calcium analyzed in a highly enriched sample. The yields of 42Ca and 44Ca were 10±5% higher than an expected yield of 43Ca. When we borrow the data by H. Voshage, the yield of 41K was also found to be apparently lower. Experimental procedures, especially the chemical procedure and the mass spectrometry of very small amount of these elements are described in detail.

Analysis of Thin Metal Films by Neutron Activation

Previously used to measure trace impurities in very pure materials have been successfully applied to the analysis of very thin metal films deposited on glass. The sample weight is approximately 50 gamma and conventional analytical methods can measure only those impurities present at relatively high concentrations. Methods are described for the quantitative determination of 11 elements on a single sample. Additional elements can be determined by modifying the chemical separation schemes. (auth)