Development of an elemental tracer using neutron activation analysis for application in an estuarine environment

Summary The work describes the selection of an activable tracer that could be used to study dispersion patterns in an English estuary and was carried out in connection with the development and testing of a particle-tracking computer model. Understanding estuarine dynamics will assist in the decision-making process for estuarine management and in contingency planning. Neutron activation analysis (NAA) has been used to characterize the concentration and natural variation of 40 trace elements in suspended particulate matter and inter-tidal bed sediment in order to identify a suitable tracer. Results have shown that europium, terbium and ytterbium would be suitable to use in a tracer study as they have low background concentrations in sediments and little variability, (Eu: 1.31 mg ^. kg^-1±13%, Tb: 0.90 mg ^. kg^-1±16% and Yb: 2.91 mg ^. kg^-1±18%). The ratios of these elements are constant throughout the estuary and experiments have shown that increases in concentration of any of these elements due to the addition of artificial elemental tracer could be quantitatively determined by changes in the ratio constant.     

Tungsten and molybdenum co-precipitation by α-benzoinoxime for activation analysis of tungsten

The co-precipitation of tungsten and molybdenum by α-benzoinoxime has been studied. Comparison of relative yields for both elements is made. Results showed coincidence and let conclude that molybdenum can be used as tracer to calculate sample to standard relative yield for tungsten. Analyses of water samples for tungsten were made and results were also presented.     

Method for the detection of Tc in seaweed samples coupling the use of Re as a chemical tracer and isotope dilution inductively coupled plasma mass spectrometry

Analysis of the artificial radionuclide ⁹⁹Tc in environmental samples requires a chemical separation due to its low concentration, and therefore the use of a chemical yield tracer is peremptory. From a practical viewpoint, Re can be used for this purpose, due to its chemical similarities with Tc. Thus, the use of a radioactive tracer for Tc recovery calculation can be avoided. However, results from a recent intercomparison exercise showed that using of Re as a chemical yield tracer appears to underestimate the Tc concentration relative to the result obtained with isotopes of Tc. In the present work, the methodology used to design a simple separation method for the measurement of ⁹⁹Tc in environmental samples is described. Tc recovery is estimated throughout the Re recovery calculation by the isotope dilution technique coupled with ICP-MS (ID-ICP-MS) technique. For chemical separation, a chromatographic resin is used. Interfering elements are removed using a resin washing step carefully designed to avoid any element fractionation between Re and Tc; the care taken in this step is of major importance to assure the equivalence of the chemical recoveries for both elements. Agreement is tested using five replicates of five seaweed samples. The average recoveries for ^95mTc and Re were 93±6 and 95±7%, respectively, those are within the uncertainty intervals for each other. The results explained here demonstrate the possibility of applying Re chemical recoveries to calculate the Tc concentrations with the advantage of not introducing systematic errors.     

Chemilumiescence immunoassay for oxazepam

For the sensitive assay descibed, antiserum against oxazepam-3-hemisuccinate/bovine serum albumin is raised in rabbits. The chemiluminogenic N-(4-aminobutyl)-N-ethylisoluminol conjugate of oxazepam-3-hemisuccinate is used as tracer. The sample or standard is incubated with a suitable antiserum and chemiluminogenic tracer for 60 min. After separation (dextrancoated charcoal) of bound and free tracer, the chemiluminescence in the bound fraction is measured. As little as 0.9 pg of oxazepam could be oxazepam could be detected. In urine samples, down to 40 ng ml^?1 could easily be determined after HPLC separation.     

Multitracer study on distribution of carrier-free radioactive isotopes in organs of rats

Multitracer, a new tracer technique developed by us, can analyze metabolism and behavior of different elements in the living bodies simultaneously. We were able to reproduce completely the results on the behavior of various elements obtained by individual experiments of our precursors only by a single run of this technique. At the same time, we could also show the behavior and interaction of many other trace elements which past researchers did not pay attention to. For example, our results on the behavior of rare-earth elements suggested that there is a correlation between their uptakes and ion radii. We also discovered that affinities of platinum and iridium for their binding proteins were changed, the latter being increased, in the case of zinc deficiency. In this article, we discuss the usefulness of the multitracer technique in the studies of trace elements in living bodies.     

Investigation of chemical separation methods for Ca and Sr. : Quantitative determination of both elements in Ca-Sr mixtures by the isotopic dilution method

The quantitative separation of Ca and Sr by sonic of the most interesting chemical procedures has been investigated, using radiochemical tracer techniques. It could be shown that no satisfactory separation could be achieved and good results are obtained in some cases by compensation of errors.The results have been used for the development of an isotopic dilution method for the determination of Ca and Sr in mixtures of their salts, Reliable results arc obtained on the semi-micro-scale.     

Neutron-produced,short-term radiotracers and activable,stable tracers in ecological studies

In three different experiments, Mn, Mo, and La were used in a dual tracer system called double activation analysis (DAA), where stable elements and neutron-induced radioisotopes of that same element are combined for tracer studies in a steam mesocosm. DAA in ecological studies is successful in overcoming problems associated with the need obtaining both immediate and long-term information in the same experiment. Analysis of the data suggests that roots growing in stream waters may serve as bioaccumulators of potentially polluting heavy metals.     

坡面侵蚀形态转变过程的REE示踪法研究

利用REE元素示踪法，采取沿坡面垂直分层布设的新的试验布设方法，通过室内模拟降雨试验，研究了次降雨条件下坡面侵蚀形态的转变过程和细沟的发育发展过程。研究结果表明，降雨初期坡面以面蚀为主，细沟出现后，坡面侵蚀将加快加剧；随着降雨时间的延续，累积面蚀量和细沟累积侵蚀量都将逐渐增加，后者的增加速率大于前者，面蚀所占总侵蚀量的百分比随降雨时间呈曲线形式逐渐递减，细沟侵蚀则逐渐增加；试验结束时细沟侵蚀量分别为面蚀量的4—5倍。本研究为定量区分片蚀和细沟侵蚀量以及坡面侵蚀过程中片蚀向细沟侵的转变以细胞侵蚀发生、发育提供了新的思路和解决途径。     

Tracer packet: A new conception for the production of tracers

The concept of tracer packet, which can be defined as a group of carrier-free radioactive isotopes of few elements, which have been produced together with an objective to study some particular physical, chemical or biological systems has been introduced in this paper. The tracer packet can be produced with low projectile energy (5-7 MeV/u) contrary to the multitracer technique. A thick cobalt foil has been irradiated consecutively with ¹⁶O, ⁷Li and ¹²C beams to produce the tracer packet containing carrier free radiotracers of Mn, Cu, Zn, Ga, Ge, As and Se which after removal of bulk cobalt can be used for further studies of essential micro nutrient elements.     

不同产地啤酒中无机元素的因子分析与聚类分析

啤酒样品经硝酸消解后,用微波等离子体炬原子发射光谱法(MPT-AES)测定其中无机元素的含量。所得结果用SPSS 17.0科学统计软件进行因子分析和聚类分析。因子分析的结果表明:总方差(52.803%)的贡献来自于代表钴、锶、锰元素的因子1和代表锌、铁、铜元素的因子2,所以这些元素是啤酒中的特征元素。聚类分析的结果表明:9种产地的啤酒可以很好地彼此区别,并以此进行啤酒产地的归属辨别。     

Backscattering techniques for the measurement of stable isotope abundances and tracers

Prompt ion beam analysis methods can be used to measure the isotopic composition of materials. When applied using microbeams of charged particles they have the potential to measure the spatial distribution of isotopes. The value of Rutherford backscattering for isotope measurement is examined both from the point of view of the measurement of stable isotope abundances and the spatial distribution of stable isotope tracers. Parametes which affect the mass resolution and sensitivity are examined including incident particle energy and mass, scattering angle, energy spread of the incident beam, detector resolution and solid angle effects. Experimental measurement of the isotopic abundances of several elements are presented including magnesium, nickel and silver. A variety of incident ions and energies and different detection systems are used. The limitations of the method are discussed and its extension to nuclear microprobe application, with its spatial tracer determination capabilities, is appraised.     

A new biosynthetic tracer for the inline measurement of virus retention in membrane processes: part II. Biochemical and physicochemical characterizations of the new tracer

In a previous work, a reproducible procedure to produce a new biosynthetic tracer was developed. This new tracer is an MS2 bacteriophage with enzymatic probes grafted on its surface, which can induce enzymatic activity of the tracer. In this paper, the biochemical and physicochemical characteristics of this new tracer are determined. A protocol was developed to determine the specific enzymatic activity kcat_TRACER of the tracer, which was found to be 2.93 ± 0.78 × 10⁴ min⁻¹ on average. Physicochemical characterizations of this new tracer showed that it is representative of viruses and may thus be used as a virus surrogate to assess the virus retention of membrane systems inline. Notably, the mean diameter and molecular weight of the tracer were found to be respectively 64.1 ± 0.3 nm and 12140 ± 3654 kDa, which are within the size and molecular weight ranges of pathogenic viruses carried by water. The tracer surface was also studied and revealed the considerable porosity of the grafted probe layer, with a mean porosity of 88%, which could explain why the zeta potential of the tracers (−14.34 ± 1.66 mV) was nearly the same as that of the native MS2 phages. Finally, a comparison between filtration of the reference microorganism used for membrane performance assessment (the MS2 phage) and the tracer suspensions showed the same filtration behaviour.     

A new approach to determine Pm in irradiated fuel solutions

Developments carried out in the Laboratory of Isotopic, Nuclear and Elementary Analyses in order to quantify ¹⁴⁷Pm in spent nuclear fuels analyzed at the CEA within the framework of the Burn Up Credit research program for neutronic code validation are presented here. This determination is essential for safety-criticality studies.The quantity and the nature of the radionuclides in irradiated fuel solutions force us to separate the elements of interest before measuring their isotopic content by mass spectrometry. The main objective of this study is to modify the separation protocol used in our laboratory in order to recover and to measure the ¹⁴⁷Pm at the same time as the other lanthanides and actinides determined by mass spectrometry.A very complete study on synthetic solution (containing or not ¹⁴⁷Pm) was undertaken in order to determine the yield of the various stages of separation carried out before obtaining the isolated Pm fraction from the whole of the elements present in the spent fuel solutions. With the lack of natural tracer to carry out the measurement with the isotope dilution technique, the great number of isotopes in fuel, the originality of this work rests on the use of another present lanthanide in fuel to define the output of separation. The yields were measured at the conclusion of each stage of separation with two others lanthanides in order to show that one of them could be used as a tracer to correct the measurement of the ¹⁴⁷Pm with the separation yield. The total yield (at the conclusion of the two stages of separation) was measured at the same time by ICP-MS and liquid scintillation. This last determination made it possible to validate the use of the ¹⁴⁷Sm (natural) to measure the ¹⁴⁷Pm in ICP-MS since the outputs determined in liquid scintillation and ICP-MS (starting from the radioactive decrease of the source having been used to make the synthetic solution) were equivalent. It is the first time that such measurement is performed in ICP-MS.The measurement of the ¹⁴⁷Pm was finally taken on fuels UOx and MOx by using the ¹⁵³Eu like a tracer of the separation yield. The results obtained are in very good agreement with those obtained from neutronic calculation code.     

Analysis of composition and growth mechanisms of oxide scales on high temperature alloys by SNMS,SIMS, and RBS

Composition and growth phenomena of alumina scales on a conventional wrought alloy Fe-20Cr-5Al and an yttria containing ODS alloy with the same base composition were investigated. The alloys were oxidized in a twostage oxidation process at 1000 °C in air and air containing¹⁸O-tracer. By using secondary neutrals and secondary ion mass spectrometry in combination with RBS, the in-depth concentration of main and minor alloying elements as well as the oxygen isotope distribution in the alumina scale could be determined. It is shown, that the difficulties in deriving the exact growth processes of the scales from the oxygen tracer profiles can be overcome by using the time dependance of the iron and chromium distribution in the alumina. From these results it could be derived that growth of the oxide scales formed on the ODS and the conventional alloy mainly differ in the relative contribution of aluminium diffusion. The mechanisms which lead to these differences in scale growth phenomena will be discussed.     

Elaboration of a programmed,semi-automated radiochemical processing system for neutron activation analysis of some volatile elements

Based on the method of SAMSAHL a programmed, semi-automated processing system has been developed and tested for the neutron activation analysis of the following elements: As, Se, Sb, Br, Sn and Te. The main characteristics of the procedure are the following: wet ashing of the sample (by means of digestion in a mixture of concentrated sulphuric acid and hydrogen peroxide), bromination, and chlorination. The procedure is controlled via the appropriate dosage of the reagents and a carefully managed thermal balance. The chemical yield and its reproducibility were determined by tracer techniques using exactly the same parameters as for the active runs. According to the results the method can be used for the routine determination of the given elements except antimony. Presented at the 4th Symposium on the Recent Developments in Neutron Activation Analysis, 1975, Cambridge.     

Selective extraction of blood plasma exchangeable copper for isotope studies of dietary copper absorption

Measuring mineral absorption by fecal monitoring is labor-intensive and relies on good volunteer compliance. Blood indicators of absorption could be advantageous and we have developed a method for selective extraction-of recently absorbed (exchangeable) copper based on dialysis of plasma with histidine and subsequent copper extraction using Chelex resin. The potential for measuring copper absorption by transient enrichment of exchangeable copper with the stable isotope 65Cu from an ingested tracer, was also investigated. This method was compared with that of the fecal monitoring technique in a human volunteer, who consumed a 6 mg dose of 65Cu with inhibitors of copper absorption. Holmium was used as a non-absorbable rare-earth marker of unabsorbed tracer excretion, allowing estimation of re-secreted 65Cu (44 microg d(-1)), and hence calculation of true tracer absorption, which was only 10.8%. Monitoring plasma tracer kinetics showed potential for estimation of copper absorption without the need for fecal copper analysis.     

Different Biotinylation Strategies for Competitive Immunoassay of Estradiol

Study on biotinylation strategies for competitive immunoassay of estradiol (E2) was carried out. Two types of competitive enzyme immunoassay (EIA) with Biotin-Avidin amplification system were established and optimized.The E2-Biotin conjugate was used as a tracer in one assay, and biotinylated antibody was used as a tracer in the other. In both of EIAs, horseradish peroxidase-labelled Avidin (Avidin-HRP) was used with a spectrometric determination of enzyme activity. The precision, sensitivity and specificity were measured and compared. The results showed that although both were satisfactory in specificity, the EIA with hapten-Biotin showed to be superior to the EIA with biotinylated antibody in sensitivity and precision. The limit of detection of serum E2 was 8 and 50 pg/mL with E2-Biotin and biotinylated antibody as tracer, respectively.     

Cation-exchange separation of hafnium and zirconium from accompanying ions

Hafnium and zirconium are not retained on the strongly acidic cation-exchange resin Dowex 50 from a mixture consisting of methanol and 12M nitric acid (19:1) which is 0.1M in trioctylphosphine oxide. On the other hand most other elements investigated are strongly adsorbed on the resin from this medium so that they are readily separated from hafnium and zirconium. These elements include titanium, rare earths, alkali metals, alkaline earth metals, iron, cobalt, manganese and zinc. This separation technique has been found to be suitable for the separation of tracer and milligram amounts of hafnium and zirconium from accompanying metal ions. If in place of methanol other organic solvents such as acetone, tetrahydrofuran and methyl glycol are used the selectivity of the separation of zirconium and hafnium from the other elements is decreased. The same effect is observed when hydrochloric acid is used in the mixtures instead of nitric acid.     

Radiotracer investigation of phosphoric acid and phosphatic fertilizers production process

In the phosphoric acid production process, the time a particle spends inside the chemical reactor (residence time) is of paramount importance to process engineers. Residence time distribution (RTD) gives information on the efficiency of the chemical reactor, on the efficiency of the process, and also the availabilities of the reactive volume for the reaction (active volume vs. dead volume). Traditionally, chemical engineers used chemical tracer to determine the RTD. However, first disadvantage is that the chemical tracer could not allow an online diagnosis: the samples containing chemical tracer have to go to a lab for analysis, second disadvantage is that the chemical tracer is less sensitive than radioactive ones because of its adsorption onto strata or its retention in rocks. Consequently, chemical tracer results are not always precise and cannot convincingly explain the multiple flow-path model. Radioactive tracers are the only tracers capable of measuring the active RTD with high degree of precision and give information on the internal recirculation rate. In this work, we will describe the application of radiotracer method for RTD measurement in the phosphoric acid production process and give results and discussion of each case encountered.