The determination of selenium status in the Australian diet using neutron activation analysis

Australia-wide samples of 50 representative foods from each of the State capitals were analysed for selenium by instrumental and radiochemical neutron activation analysis. Results were compared with State and Federal Regulations for toxic elements in foods as well as with recommendations by Australian and US authorities for safe and adequate dietary intake of this essential trace element.     

Trace elements in Australian opals using neutron activation analysis

Neutron activation analysis was used to determine the concentration of trace elements in 42 samples of black, grey and white opals taken from a number of recognised Australian field. The results were evaluated to determine if a relationship existed between trace element content and opal colour.     

The determination of manganese in seawater,surface water and rainwater by neutron activation analysis

A rapid procedure for the determination of manganese in seawater, surface water and rainwater is presented. The method is based on preconcentration of manganese as the pyrrolidine-dithiocarbamate (APDC) complex on a layer of active carbon and determination of the manganese in the carbon concentrate by neutron activation analysis. Provided the blank of the carbon can be kept low the limit of determination is 50 ng Mn·l⁻¹, when a sample of 200 ml is processed.     

Low level determination of manganese in biological reference materials by neutron activation analysis

A simple method was developed for the low level determination of manganese in biological materials by neutron activation analysis with radiochemical separation based on manganese dioxide precipitation. Precision and accuracy of the method were tested by analyses of IAEA reference materials Animal Muscle H-4, Milk Powder A-11, Freeze Dried Animal Blood A-13, Horse Kidney H-8, and Mixed Human Diet H-9. Interferences from iron and cobalt were also evaluated.     

Selenium status in the blood of Australians using neutron activation analysis

Selenium determination by neutron activation analysis via both short and longlived selenium isotopes was performed on 98 samples of whole blood taken from Sydney workers. Half of the samples were further separated into their compenents and selenium measured on the erythrocyte and plasma fractions. The average selenium concentrations for blood, plasma and erythrocytes were 0.103, 0.091 and 0.117 g·ml^–1, respectively. These are compared with literature values for Australia and other countries.     

Trace level determination of manganese in liver tissues employing substoichiometric thermal neutron activation analysis

Liver tissues from rat have been analyzed for determining trace amounts of manganese present by employing thermal neutron activation analysis and substoichiometric solvent extraction of Mn/II/ with 1,2,3-benzotriazole into 1-octanol. Three samples and a standard can be processed and counted within three hours.     

Nondestructive and destructive determination of manganese in nickel- and iron-base alloys by neutron activation analysis

Nondestructive and destructive methods are described for the determination, by neutron activation, of small amounts (more than about 0.001%) of manganese in nickel- and iron-base alloys. In the destructive method, thenoyltrifluoroacetone (TTA) extraction has been applied to the separation of manganese after irradiation.     

The determination of trace elements in new food grain SRM's using neutron activation analysis

Potentially toxic metals in the food chain that can lead to deleterious effects on human health have been well documented. Because of the toxicity of some metals, levels of 1 ppm or less must be routinely monitored in foods to ensure human safety. To ensure the accuracy of measurement, NBS in a cooperative interagency agreement with the Food and Drug Administration is involved in developing and certifying selected elements in food grain as a part of the Standard Reference Material program. Both instrumental and radiochemical neutron activation analysis were used to analyze two food grain standard reference materials (Rice and Wheat Flours) for trace element certification.     

Determination of manganese in ores by activation analysis using a californium-252 neutron source

A²⁵²Cf neutron source has been used to analyse manganese in ores such as pyrolusite, rodonite (manganese silicate) and blends used in dry-batteries. Samples with about 150 mg and standards of manganese dioxide were irradiated for about 20 min and counted using a well-type NaI(Tl) scintillation counter and scaler, with or without pulse-height discriminator between the detector and the scaler. The interferences of nuclear reactions⁵⁶Fe(n,p)⁵⁶Mn and⁵⁹Co(n,α)⁵⁶Mn were studied, as well as problems in connection with neutron shadowing during irradiation, gamma-rays attenuation during counting and influence of granulometry of samples. Some of the samples were also analysed by wet-chemical method (sodium bismuthate) in order to compare results.     

The determination of sampling constants by neutron activation analysis

It has been found that sampling constants vary greatly not only from major elements to trace elements, but also between individual trace elements. A comprehensive investigation of a potential reference material therefore requires the determination of sampling constants for all elements to be certified, and other analytical methods therefore have to be included. For methods in statistical control the described strategy can be applied.     

The determination of bromine in rocks by neutron activation analysis

A neutron activation method for the determination of bromine in rocks and minerals is described. After removal of iodine, bromine is separated by oxidation with potassium permanganate and extraction with carbon tetrachloride. Bromine is thon precipitated as silver bromide; yields are from 60 to 84%. The method has a sensitivity of 0.001 p.p.m. of bromine and is free from interfering reactions. The values obtained for G-1 and W-1, 0.484 and 0.490 p.p.m. of bromine respectively, are lower than the average values for granites and basalts previously reported.     

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.     

Non-destructive determination of aluminum in biological reference samples using neutron activation analysis

The non-destructive methods of thermal and epithermal neutron activation analysis have been employed to determine the aluminum concentration of seven National Institute of Standards and Technology certified biological reference materials. Through the judicious use of both thermal and epithermal neutron activation analysis using bare and boron-lined irradiation carriers, the major and minor contributions of the³¹P/n, /²⁸Al and of the²⁸Si/n, p/²⁸Al reactions, respectively, to the²⁷Al/n, /²⁸Al reaction could be corrected for explicitly. Based on replicate determinations precision of the analysis ranged from 2.5% for citrus leaves determined at the 75 ppm level to 18% for bovine liver measured at the 1 ppm level. Accuracy was demonstrated whenever possible by comparison to existing published data.     

Precision analyses of manganese in rocks by neutron activation analysis

A simple and rapid procedure for the determination of manganese in rocks by neutron activation and γ-spectrometry is presented. The precision of the method calculated from analyses of standard rocks is of the order 1.5–2%, and an accuracy of ±2% is attainable. The method is applicable to most types of geological samples, and should be superior to conventional methods used in rock analysis.     

The simultaneous determination of 235U and 239Pu using delayed neutron activation analysis

Delayed neutron activation analysis (DNAA) remains one of the most sensitive methods of nondestructively determining fissile materials in a variety of sample matrices, provided that the samples contain only a single fissile component. This has historically been the limiting factor in many applications of DNAA, and often chemically destructive methods of analysis have needed to be utilized for many real-world samples. This work seeks to develop a method that will allow for DNAA to be utilized on samples containing multiple fissile components. Initial efforts, presented here, show that using a multivariate linear regression model to describe the delayed neutron emission profile of an irradiated sample allows for the concurrent determination of fissile nuclides in samples containing both ²³⁵U and ²³⁹Pu, without chemical separations and using only a single counting step.     

The determination of rhenium in flue dust by neutron activation analysis

Rhenium was determined by radiochemical neutron activation analysis in flue dust samples of complex chemical composition. Two separation techniques were used; distillation from perchloric-hydrochloric acid solution and hydroxide scavenging followed by extraction with tetraphenylarsonium chloride in chloroform. ¹⁸⁶Re and ¹⁸⁸Re were measured with a Ge(Li) low-energy photon detector. Chemical yields were determined by reactivation. For a neutron flux of 5·10¹¹ n cm^-2 s^-1, an irradiation time of 6 h and samples of ca. l g, down to 50 p.p.b. of rhenium could be determined.     

The determination of iodide in sea water by neutron activation analysis

A simple and sensitive method for the determination of iodide in sea water by neutron activation analysis has been developed. Iodide is separated from most other anions by passing sea water through a strongly basic anion-exchange column, recovered by elution with 2 M sodium nitrate, and concentrated from the eluate by precipitation as palladium(II) iodide in the presence of excess of palladium(II) with elemental palladium as carrier; elemental palladium is generated by reduction of some of the palladium(II) with thiosulfate. The precipitate is separated from the supernatant liquid by filtration. Checks on the efficiency of separation by means of added ¹²⁵I showed recoveries of 100 ± 3 %. The filter paper containing the precipitate is pressed into a pellet for neutron activation analysis by irradiation for 5 min at a flux of 4 ·10¹² n cm^?2 s^?1 and counting the ¹²⁸I 442.7-keV photopeak.     

The determination of nickel in air dust by neutron activation analysis

The determination of nickel in atmospheric aerosols, collected on filter paper, is performed by thermal neutron activation analysis using the⁶⁵Ni (T=2.56 h) isotope. Liquid-liquid extraction and anion-exchange are applied in the chemical separation. The absolute sensitivity of the method is ≌0.02 μg Ni. The relative sensitivity is 0.005 μg Ni/m³ if an air sample of about 1000 m³ is used.