Determination of129I in soils of Germany using radiochemical neutron activation analysis

At 5 sampling sites distributed throughout Germany the¹²⁹I concentrations in soils have been measured in individual depth intervals to a depth of 60 cm. These measurements are used to determine the total amount of¹²⁹I in a soil column of 60 cm depth. The data indicate that the¹²⁹I concentrations and the¹²⁹I/¹²⁷I isotope ratios are higher at the sampling locations near the coast compared to the sampling locations in Southern Germany. The total¹²⁹I inventories in the top 60 cm of soils are correlated with the¹²⁹I deposition through rainfall.     

Determination of phosphorus in steels by radiochemical neutron activation analysis

The viability of radiochemical neutron activation analysis as a method for certification of phosphorus in steels was tested by analysis of SRM low alloy steels. Preliminary results are generally in agreement with certified values. The limit of detection, as defined by Currie¹, was determined to be 5 μg/kg.     

Determination of antimony in tin by radiochemical neutron activation analysis

New types of correction for chemical yield and counting geometry in conjunction with the comparator method provide significant improvements in reproducibility and sensitivity compared to direct neutron activation analysis.     

Trace analysis of ancient gold objects using radiochemical neutron activation analysis

Radiochemical neutron activation analysis has been applied to investigate the microelements in gold samples with archaeological importance. Chemical separation has allowed the determination of traces of Ir, Os, Sb, Zn, Co, Fe, Ni. Instrumental neutron activation analysis has been used for the determination of Cu.     

Determination of rare-earth elements in steels by radiochemical neutron activation analysis

For the separation of rare-earth elements from steel, with a cation exchange resin, separation experiments were performed on NIST reference materials of SRM-363 and SRM-364. Iron, Na, Cr, Mn, Co, Cu, As, Mo, Sb and W were separated in 2M hydrochloric acid, five rare-earth elements, La, Ce, Pr, Nd and Sm and three other elements, Hf, Zr and Ba were separated using 8M nitric acid. Each element was determined by a single comparator method using two monitors, gold and cobalt.     

Determination of impurities in tantalum by a radiochemical neutron activation analysis

A radiochemical separation method using Dowex 1×8 (200–400 mesh) has been applied to two tantalum metals of 99.9% purity. While tantalum was still retained on the resin, the elements Na, K, Cr, Mn, Fe, Co and Zn were separated with 2M HF and subsequently the elements Sc, As, Zr, Mo, Eu, W and Hf with a mixture of 0.5M HF and 3M HCl. The separation yields for all impurities was 98–100%. Elemental contents were calculated by a single comparator method using two monitors.     

Determination of gold in biological materials by radiochemical neutron activation analysis

A radiochemical neutron activation analysis procedure was developed for the determination of trace amounts of gold in biological materials. The procedure was realized with irradiation of reference and test samples in a nuclear reactor, selective and quantitative separation of gold using inorganic MnO₂ Resin and gamma-ray spectrometric measurement of ¹⁹⁸Au. The method is characterized by a low limit of detection of gold at ng g^?1 level. Results shows that the method can be applied to the determination of trace amounts of gold in tissues for medical research.     

Determination of cadmium by substoichiometric thermal neutron activation analysis

A rapid and selective method has been developed for the determination of cadmium in environmental samples by thermal neutron activation analysis, employing substoichiometric solvent extraction technique. Alcoholic solution of 2-mercaptobenzothiazole /2-HMBT/ has been used for the substoichiometric extraction of Cd/II/ from an aqueous solution of pH 7.0 into methyl iso-butyl ketone /MIBK/.     

Determination of U and Th in tungsten by radiochemical neutron activation analysis

A radiochemical separation method using an anion exchange resin has been applied to 4N grade tungsten for determining U, Th and 4 other elements. While tungsten remained in the resin, Na, K and As were separated with 0.05M HCl and 1M HF and then U, Th and Cr were eluted with 1M HCl and 1M HF. The separation yield of neptunium (U) was influenced largely by the amount of thorium, but this influence could be neglected as the concentration of the thorium was below 0.5g/ml. The content of these elements were calculated by a single comparator method using monitors, gold and cobalt. The detection limits of U and Th are 4.0 and 1.2 ppb, respectively.     

Determination of selenium in human diets by radiochemical neutron activation analysis.

A post-irradiation radiochemical separation technique was tested for the determination of selenium levels in diet samples, collected by using a duplicate portion technique, from both rural and urban population groups in Turkey. The technique involved sample irradiation, acid digestion, selective distillation, precipitation and filtration steps. During the separations it was possible to determine the yield of each sample using a stable selenium carrier. An average chemical yield of 71 +/- 3% was obtained for the radiochemical neutron activation analysis. For samples from urban and rural regions, the average selenium concentrations obtained were 0.14 +/- 0.04 and 0.07 +/- 0.02 mg kg-1, respectively. It was also possible to determine daily dietary selenium intakes, which were found to be 81 +/- 41 micrograms and 23 +/- 11 micrograms for the urban and rural groups, respectively. Although daily selenium intakes were found for a small number of subjects in this study, the separation technique developed can be used for determination of the selenium status in larger population groups.     

Determination of impurities in niobium metal by a radiochemical neutron activation analysis

A radiochemical separation method using an anion exchange resin has been applied to 3N grade Nb for determining nine impurity elements. Five elements (Cr, Fe, Co, Zn and Se) were separated in 2M HF, three elements (Mo, W and Hf) in 32M HF, Nb in 0.5M HF/3M HCl, and Ta in 1M NH₄F/4M NH₄CCl. The contents of the elements were calculated by a single comparator method using two monitors of Au and Co. The main impurity was revealed to be Ta with a content of over 160 ppm.     

Rapid radiochemical separations in neutron activation analysis using ion retention media

A rapid radiochemical procedure based on the removal of mercury, selenium, arsenic and antimony by columns of C₁₈-bonded silica gel or activated carbon after their selective complexation in sulphate/nitrate media by ammonium pyrrolidine-dithiocarbamate, diethylammonium diethyldithiocarbamate, potassium ethyl xanthate, bismuthiol II or 8-hydroxyquinoline, was examined. Comparisons were made of the ability of the two ion retention media to remove these metal ions and to allow their regeneration and recycling. The effectiveness of this technique was demonstrated by analysis of horse kidney and human diet, International Atomic Energy Agency biological reference materials, for mercury and selenium.     

Low-level determination of silicon in biological materials using radiochemical neutron activation analysis

Summary A new radiochemical neutron activation analysis (RNAA) method has been developed for low-level determination of Si in biological materials, which is based on the ³⁰Si(n,γ)³¹Si nuclear reaction with thermal neutrons. The radiochemical separation consists of an alkaline-oxidative decomposition followed by distillation of SiF₄. Nuclear interferences, namely that of the ³¹P(n,p)³¹Si with fast neutrons, have been examined and found negligible only when irradiation is carried out in an extremely well-thermalized neutron spectrum, such as available at the NIST reactor. The RNAA procedure yields excellent radiochemical purity of the separated fractions, which allows the measurement of the β^--activity of the ³¹Si by liquid scintillation counting. Results for several reference materials, namely Bowen’s Kale, Bovine Liver (NIST SRM 1577b), Non-Fat Milk Powder (NIST SRM 1549) and several intercomparison samples, Pork Liver-1, Pork Liver-2 and Cellulose Avicel, are presented and compared with literature values.     

Determination of traces of phosphorus in gallium arsenide by radiochemical neutron activation analysis

A radiochemical separation procedure has been developed to determine traces of phosphorus in gallium arsenide. In this procedure the indicator nuclide³²P is separated from all other long-lived activation products in high purity. The resulting eluate is sufficiently pure to allow -counting. Because of the high -energy of³²P (1710 keV) the activity can be measured via the Cerenkov effect, whereas most radionuclides, because they have essentially lower -energies, are discriminated by this technique, so that the selectivity of the measurement of³²P is improved considerably. A detection limit of 1 ng/g was achieved when using samples of 50 mg, a thermal neutron flux of _th=1·10¹³n·cm^–2·s^–1, an irradiation time of 36 hours and a measuring time of 1 hour.     

Determination of iodine in human brain by epithermal and radiochemical neutron activation analysis

Despite the role of iodine for proper development of the brain and the functions of the element, the accurate data on its concentration in brain tissue are largely lacking, the main reason being analytical difficulties associated with determination of the element especially at low levels. In this work, samples from human brain regions from Hungarian patients were analyzed using epithermal and radiochemical neutron activation analysis (ENAA and RNAA, respectively). The RNAA procedure is based on alkaline-oxidative fusion followed by extraction of elemental iodine in chloroform. The results were checked by the analysis of biological standard reference materials, namely bovine liver, bone meal and diet, and by comparison with previous results obtained by a different RNAA procedure.     

Determination of iodine in Asian diets by epithermal and radiochemical neutron activation analysis

Samples of diets from China, Japan, Korea, India, Pakistan and Philippines were analyzed using epithermal and radiochemical neutron activation analysis (ENAA and RNAA, respectively) within the framework of the IAEA project “Reference Asian Man”. The RNAA procedure was based on alkaline-oxidative fusion followed by extraction of elemental iodine in chloroform. The analytical methods employed are discussed in terms of detection limits and uncertainties of the results obtained. For quality control purposes a number of NIST biological reference materials, namely diets and foods were analyzed. Results for the diet samples indicate that achieving the WHO recommended daily allowance for iodine may be a problem in most of the above given countries. This revised version was published online in August 2006 with corrections to the Cover Date.     

On processing standards in radiochemical neutron activation analysis

In radiochemical neutron activation analysis, standards may be measured directly or subjected to the same radiochemical processing as the sample. Some considerations in regard to processing are examined, and the advantages and disadvantages of this approach discussed. It is concluded that processing of standards is often inadvisable and can lead to errors, particularly if used as a substitute for radiochemical yield determinations.     

Determination of impurities in titanium and titanium oxide by radiochemical neutron activation analysis

A radiochemical neutron activation analysis has been applied to 2N–4N grade titanium metal and its oxide. Twenty two impurities were separated in a group from scandium by a radiochemical separation method using cation exchange resin with HBr and HCl. The contents of the elements were calculated by a single comparator method using two monitors. The analytical results agree well within 10% deviation with those obtained by instrumental method. Eighteen elements, Na, Fe, Co, As, Se, Sr, Mo, Sb, La, Eu, Tb, Yb, Lu, Hf, Ta, W, Th and U, are determined in titanium oxides and 17 elements, Na, Cr, Fe, Co, Se, As, Zr, Mo, Sb, Cs, Ce, Tb, Yb, Hf, Ta, W and Th, in titanium metals.     

Determination of Fe and Zn in biological samples by radiochemical neutron activation analysis

Radiochemical NAA methods have been developed for the simultaneous determination of Fe and Zn in biological samples. The method involves reactor irradiation, dissolution in 3M HCl and solvent extraction followed by counting on a scintillation gamma-ray spectrometer. Iron was separated with aqueous cupferron and extracted into chloroform while Zn was extracted with 2-thenoyl trifluoroacetone (TTA) into methyl isobutyl ketone (MIBK). Reaction conditions such as pH and the effect of solvents and various ions were studied using tracer activities. The methods have been employed for trace level determination of Fe and Zn in NBS, SRMs, Bowen's Kale, IAEA CRMs and other plant leaves.