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11.
R. Jaćimović V. Stibilj L. Benedik B. Smodiš 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(3):545-549
The neutron distribution in a defined volume (gradient) for different matrices (air, water, cellulose, biological material and silicon dioxide) in two typical irradiation channels (pneumatic tube (PT) and IC40-channel in the carousel facility) in the TRIGA Mark II reactor at the Joef Stefan Institute (IJS) was studied. Our experiment was based on inserting Fe wires (flux monitors) into the chosen matrices. The wires were cut into small pieces after irradiation and the induced activities of 59Fe measured. The results showed that for the studied geometry the average spatial thermal neutron flux inhomogeneities (for five studied matrices) are about 2.3% in the PT-channel and about 2.9% in the IC40-channel. 相似文献
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Summary A radiochemical neutron activation analysis (RNAA) for simultaneous determination of uranium and vanadium in a single sample at trace levels is described. The method is based on post-irradiation wet-ashing and solvent extraction of vanadium with N-benzoyl-N-phenyl-hydroxylamine reagent. From the remaining aqueous phase, uranium is extracted into a toluene solution of tri-n-butyl phosphate. The chemical yields are determined spectrophotometrically for vanadium and by gamma-counting of the added natural uranium carrier for uranium. The method was evaluated by the analysis of reference materials and the results showed a good agreement with the certified values. The method was applied to the determination of vanadium and uranium in five military total diet samples in Slovenia. 相似文献
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The paper addresses identification of industries and activities handling NORM and inventory of TENORM in Slovenia. The identification is based on survey of historical information available, results published in scientific papers, research reports made by research institutions within Slovenia, as well as original research aimed at obtaining more detailed picture of the areas investigated. For this purpose, gamma dose-rate measurements were performed on site, sampled TENORM/NORM materials were measured by high-resolution gamma spectrometry for determination of 210Pb, 238U, 232Th, 228Th and 226Ra. Waste water and ground water samples were analysed for 238U, 226Ra and 210Pb using RNAA, LSC and beta proportional counting. The inventory of the investigated sites is presented, giving the information on amounts of the deposited wastes, specific activities of the natural radionuclides and geographical distribution of the inventories in Slovenia. 相似文献
14.
Nanogram and picogram quantities of uranium were determined in biological materials by radiochemical neutron-activation analysis. Two different approaches using either (239)U or (239)Np were employed for cross-checking, and the question of negative errors due to incomplete acid dissolution of any possible inorganic (siliceous) fraction was studied. In the first and main approach, radiochemical separation of the short-lived (239)U (23.5 min) nuclide was based on TBP extraction following rapid conventional wet-ashing. Addition of large amounts of uranium carrier (ca. 50 mg) allowed the chemical yield to be evaluated from the gamma spectrum of the isolated fraction by means of the 186 keV peak of (235)U. In the second approach, the longer-lived (239)Np (56.5 hr) daughter was separated by anion-exchange; this nuclide allowed use of lengthier dissolution procedures employing total decomposition with hydrofluoric acid. Nanogram quantities of (237)Np were irradiated simultaneously with the sample and an aliquot of the resulting solution containing (237)Np and (238)Np (51 hr) was added prior to sample destruction, these isotopes serving as carrier and yield tracer, respectively. Results are presented for a series of reference materials. The methodologies and results from the two approaches are discussed and evaluated. 相似文献
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Being aware of the importance to consider every step in the evaluation of the combined measurement uncertainty of the result,
the purpose of this work was to evaluate the contribution of the radial thermal neutron flux gradient to the uncertainty budget
for trace level uranium determination in biological materials by a radiochemical neutron activation analysis (RNAA). Determination
of uranium via the short-lived nuclide 239U was based on solvent extraction with TBP and measurement of the chemical yield from the gamma-ray spectrum of the isolated
fraction via 235U. It has been shown previously, that radial neutron flux gradient, could have a relevant effect on the final result obtained
by RNAA. In the present work, radial neutron flux gradient within the irradiation assembly generally accepted in our lab (standards
tapped beside the sample), varied between 93 and 108% around the mean value and contributes approximately 20% to the combined
measurement uncertainty of the result. 相似文献
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18.
Determination of vanadium in biological and environmental samples by RNAA with emphasis on quality control 总被引:3,自引:0,他引:3
Summary In the present work an improvement of radiochemical neutron activation analysis for determination of nanogram levels of vanadium is described. The method is based on post-irradiation wet ashing and solvent extraction of vanadium with N-benzoyl-N-phenyl-hydroxylamine (BPHA) forming a violet chelate complex in strongly acidic medium. For quality assurance purposes a procedure for determination of the overall chemical yield using spectrophotometry of the V-BPHA complex is described, and possible interferences are evaluated. The procedure was applied to the determination of vanadium in reference materials and selected food samples from Slovenia. 相似文献
19.
Total metal concentrations were determined in the serum of 12 continuous ambulatory peritoneal dialysis (CAPD) patients and in fresh and spent CAPD fluids by electrothermal and flame atomic absorption spectrometry (ETAAS, FAAS). Concentrations of Cu in serum of CAPD patients ranged from 720 to 1780 ng cm−3, Rb from 128 to 346 ng cm−3, Al from 10 to 72 ng cm−3, Fe from 800 to 2300 ng cm−3 and Zn from 659 to 1310 ng cm−3. The accuracy of the analytical procedure was checked by the analysis of the reference material Seronom™, Trace Elements in Serum. Good agreement between the certified and determined values was obtained for Al, Cu, Fe and Zn. The data on the total metal concentrations in CAPD fluids indicated that during CAPD fluid exchange the losses of Cu from 5.0 to 35 ng cm−3, of Rb from 50 to 110 ng cm−3 and of Al from 3.0 to 14.0 ng cm−3 occurred through the peritoneal membrane. Although fresh CAPD fluids contained traces of Fe (3.0-5.0 ng cm−3), the transfer of this element took place through the peritoneal membrane into spent CAPD fluid (13.0-38.0 ng cm−3). Zn concentrations were in general lower in spent (20.0-80 ng cm−3) than in fresh CAPD fluids (∼100 ng cm−3). To follow the mechanisms of the transfer of trace elements through the peritoneal membrane of CAPD patients, fractionation of metals was carried out in spent CAPD fluids by size exclusion chromatography with UV and AAS detection, applying Superdex HR 10/30 column. The chromatographic run was followed at 278 nm and separated metal species also determined ‘off line’ in 1 cm3 fractions by ETAAS or FAAS. From the UV chromatograms and AAS analysis of trace elements in the separated fractions it was demonstrated that Cu, Al, Fe and Zn were bound to proteins and only partially to low molecular weight (LMW) species, while Rb was associated exclusively with LMW species. For characterisation of the high molecular weight (HMW) binding proteins, fractions containing trace elements were subjected to SDS-PAGE electrophoresis. Al and Fe were presumably bound to transferrin, but due to its low concentration in spent CAPD fluids, it was not possible to confirm its presence in the separated fractions. About 10% of Al and 15% of Fe corresponded to LMW species. A fraction of HMW proteins of Cu in spent CAPD fluids was most probably bound to albumin and Zn to albumin and globulins. About 50% of Cu and Zn existed in LMW proteins, while Zn was also found partially in ionic form. 相似文献
20.
A chemiluminescence (CL) micro-flow system is presented for rapid determination of chemical oxygen demand (COD) in water at
room temperature. In this system, potassium dichromate is reduced to Cr3+ in 2 mol L−1 H2SO4 during the chemical oxidation of COD substances in the sample, and Cr3+ can be measured with the help of the luminol-H2O2 CL system. The polymethyl methacrylate micro-flow chip with discrete microdroplet sampling was used here. Effects on COD
determination (such as pH, concentrations, the channel length, and interference) were investigated. The linear range for COD
determination was 0.27–10 g L−1, and the detection limit was 100 mg L−1. The method was successfully applied to the determination of COD in wastewater samples. The data obtained with the present
method were in fairly good agreement with those obtained by the titrimetric method.
Correspondence: Zhujun Zhang, Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry
and Materials Science, Shaanxi Normal University, Xi’an 710062, P.R. China; Department of Chemistry, Institute of Analytical
Science, Southwest University, Beibei, Chongqing 400715, P.R. China 相似文献