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.     

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 microelements in thyroids of the inhabitants of Belarus by neutron activation analysis using thek 0-method

The k ₀-method of neutron activation analysis has been tested for applicability to the determination of trace elements in samples of thyroids of inhabitants from regions in Belarus affected to different degree by thyroid cancer among children after the accident of the Chemobyl power plant. It is shown that thek ₀-method produces results identical to the relative method in neutron activation analysis. Significant differences in the elemental composition of thyroids from the regions of Gomel and Minsk are observed and may be related to the different levels of occurrence of thyroid cancer among children.     

Substoichiometric determination of chromium by neutron activation analysis

A method of radioactivation analysis has been developed for the determination of chromium. It is based on the substoichiometric extraction of chromium diethyldithio-carbamate into methyl-isobutyl-ketone from acetate buffer solution in the presence of EDTA and potassium cyanide. The method has been applied for the determination of chromium in high-purity calcium carbonate and NBS glasses as standard reference materials.     

Substoichiometric determination of palladium by neutron activation analysis

A method is described for the substoichiometric determination of traces of palladium by neutron activation analysis involving the extraction of palladium with isonitrosoacetophenone. The sensitivity of the method is 0.005 μg of Pd. With 200 mg of silver alloy containing 0.0005% palladium, the average of three determinations of Pd is 0.98 μg, which varies between 1.07 μg and 0.91 μg at 95% confidence limit. The time required for radiochemical purification and counting of the sample does not exceed 12 minutes. Part of this work was presented at the International Conference on Modern Trends Activation Analysis, held in Gaithersburg, Maryland, USA, October 7–11, 1968.     

Substoichiometric determination of mercury by neutron activation analysis

A method has been developed for the substoichiometric determination of mercury by thermal neutron activation analysis, based on the selective extraction of the Hg(II)—Bindschedler's Green complex into 1,2-dichloroethane. The method has been applied for the determination of trace amounts of mercury in geological standards such as W-1, GR, Sye-1, and T-1, meteorite Allende de Publito, and biological materials such as kale, IR1 standard tobacco, and human blood serum.     

Substoichiometric determination of Cd by neutron activation analysis

A rapid method has been developed for the determination of cadmium in environmental samples by thermal neutron activation analysis involving substoichiometric extraction with 1,2,3-benzotriazole /1,2,3-BT/. Cd was radiochemically separated as CdS using 1-amidino-2-thiourea. The time required for radiochemical purification containing two samples and a standard was about 2 h. 4.63 g of Cd can be determined with an accuracy of 6.69% and precision of 6.25%. Mash potatoes, animal bones, raw sludge and cattle manure have been analyzed by this method.     

Substoichiometric determination of gold by neutron activation analysis

A rapid method has been developed for the determination of gold in catalyst samples by thermal neutron-activation analysis incorporating substoichiometric solvent extraction of Au/III/ with 1,2,3-benzotriazole /1,2,3-BT/ into n-butanol. The time required for radiochemical purification and counting of two samples and a standard was 1 h.     

Substoichiometric determination of tungsten by neutron activation analysis

A method for the substoichiometric determination of tungsten by thermal neutron activation analysis has been developed based on the selective extraction of the tungsten dithiol complex into amyl acetate. The method is simple, rapid and accurate. It has been used in the determination of tungsten in alloy steel, meteorites and biological standard kale.     

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 manganese status in the Australian diet using neutron activation analysis

Fifty representative foods sampled Australia-wide from each of the State capitals were analysed for manganese by instrumental neutron activation analysis. Calculated daily intake of manganese for Australian diets was compared with recommendations by US authorities for the safe and adequate dietary intake of this essential trace element. The contribution of tea to adult daily intakes was determined.     

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.     

Rapid determination of antimony in biological and environmental samples using instrumental neutron activation analysis

A rapid non-destructive activation analysis method has been developed for the determination of antimony. A high resolution low energy Ge detector is used to measure the 61.6 keV γ-ray from^122mSb (T=4.2 min). Sensitivities and detection limits for biological and environmental samples activated with thermal and epithermal neutrons are listed. The time required for the anlaysis is about 12 min per sample using thermal activation and 22 minutes using epithermal activation analysis.     

Prompt-gamma neutron activation analysis using an isotopic neutron source

This paper describes an experimental set up using an isotopic neutron source with graphite, preferably to a hydrogen-rich compound, as moderator. This low thermal flux source has been employed in PGNAA experiments. Only those elements having a high cross section can be quantitatively analyzed at low concentration levels, mainly, Gd, Cd, Sm, B and Hg; the other elements can only be probed at macroscopic levels. An application to the determination of boron content in collyria examplifies the possibilities of the technique.     

Multielemental determination in water by neutron activation analysis

Instrumental neutron activation analysis (INAA) technique has been applied to a water sample to determine the elemental concentrations. The sample was irradiated at a neutron flux of 1.2·10¹² n·cm^–2·s^–1 for two different periods followed by counting at three different decay times, using two coaxial type high-resolution Ge(Li) detectors. The dominant elements detected in the water sample are Ca, Cl, Na, Mg, and K present in levels while Co, I, Mn, Sm, and Sb are present in smaller amounts approximately on the average 0.01 ppm. Only traces of other elements such as rare-earth elements, Ag, As, Ba, Cu, Cd, Fe, Sr, W, Zn, seem to be present in the water samples.     

Rare earth element determination in silicate rocks using neutron activation analysis and mass spectrometry

A pre-irradiation group separation procedure for the quantification of 11 to 13 rare earth elements (REE) in geological materials by neutron activation analysis, with yield determination by mass spectrometry isotope dilution analysis of Sm and Nd, is described. Utilization of the shorterlived isotopes of the REE allow sufficient data for most geochemical studies to be obtained within one day of irradiation, although where necessary additional information may be obtained following a decay period of three to four weeks. Analysis of selected USGS rock standards shows the method to be both accurate and precise.     

Simultaneous determination of aluminium and phosphorus by neutron activation analysis

With the use of the pneumatic tube system of the BER II reactor, the irradiation position of which is equipped with a movable cadmium shield, the aluminium and phosphorus levels in bone powder and in human bone biopsies were determined. The contribution of aluminium and phosphorus to the²⁸Al activity could be separated mathematically after the samples had been irradiated with and without cadmium shielding. The sensitivity and limit of quantitative determination of the analytical procedure were determined using the addition method and the fact that the levels of each element measured was independent of the amount of the other element was proved.     

Fast determination of molybdenum and tellurium by neutron activation analysis

The utilization of 14.6-min ¹⁰¹Mo and 25-min ^101gTe for the determination of molybdenum and tellurium in biological materials by radiochemical neutron activation analysis is described for the first time. Radioisotopes were separated from the samples activated in a thermal neutron flux of about l0¹⁴n cm^-2 s^-1. The radiochemical procedure for molybdenum involves extraction of Mo⁺⁺ from 6 M HCl into diethylether, re-extraction into water, precipitation as oximate, and measurement of the gamma activity of ¹⁰¹Tc. The tellurium was separated by reduction to the element with SO₂ in 3 M HCl, dissolution in HNO₃, and reprecipitation as the element for the measurement of radioactivity. The sensitivity was estimated at ca. 10 ng at the level of confidence of 95%. The methods were tested by analyzing NBS- standard Bovine Liver and Orchard Leaves for molybdenum; the concentrations found were 3.2 ± 0.1 μg g^-1 and 300 ± 60 ng g^-1, respectively. The tellurium content of bovine liver was estimated at 90 ± 15 ng g^-1.     

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.     

Reference values in blood from inhabitants of Brazil: Br,Cl, K and Na determination using NAA

In this study, bromine (Br), chlorine (Cl), potassium (K) and sodium (Na) were measured in the blood of Brazilian inhabitants from Southeast (S) and Northeast (N) regions. A reference range was established as a function of sex and considering lifestyle factors (non-smokers and non- drinkers). For both regions lower values of K were found in females when compared to males and lower values of Na were found in males compared to females. Increasing trends for Na and Br were observed in the Northeast region.