Rare-earth elemental analysis of banded iron-formations by instrumental neutron activation analysis

Representative banded iron-formations (BIFs) from various locations of the eastern Indian geological belt were investigated by instrumental neutron activation analysis (INAA). After pre-concentration, irradiation was carried out using a neutron flux of 5.1·10¹⁶ m⁻²·s⁻¹, 1.0·10¹⁵ m⁻²·s⁻¹ and 3.7·10¹⁵ m⁻²s⁻¹, with thermal, epi-thermal and fast neutrons, respectively. The activities in these samples were measured by a HPGe detector. Ten rare-earth elements, such as La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb and Lu, have been qualitatively identified and quantitatively estimated in these samples. The present investigation is an example of employing a pre-concentration method for high iron-containing ores prior to neutron activation analysis.     

Determination of trace vanadium in soil by cloud point extraction and graphite furnace atomic absorption spectroscopy

This work describes a new analytical procedure for trace vanadium by graphite furnace atomic absorption spectroscopy coupled to cloud point extraction (CPE) as the separation-preconcentration method. The CPE behavior of vanadium using methylene blue as complex agent and Triton X-100 as a surfactant was investigated systematically. Under the optimized conditions, the detection limit was 0.7 ng · mL⁻¹, and the relative standard deviation was 4.3% for vanadium (c = 50.0 ng · mL⁻¹, n = 5). The recovery of vanadium was in the range of 98.9–102.8%. The method was applied to the analysis of vanadium in certified reference materials and real samples. The results obtained were in good agreement with the certified values. Correspondence: Xiashi Zhu, Key Laboratory of Environmental Material and Environmental Engineering of Jiangsu province/College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, P.R. China     

Aktivierungsanalytische Bestimmung von Chrom und Zink in biologischem Material

An activation analysis method has been developed for the determination of chromium and zinc in biological material. After the samples had been activated in a thermal flux of 7·10¹¹ n·cm⁻²·sec⁻¹ for 100 hours, both elements were separated from interfering radionuclides by means of ion-exchange and distillation processes. Gamma spectrometry was used to measure the activities of⁵¹Cr and⁶⁵Zn. The practical limits of detection were found to be 1·10⁻⁸ g for chromium and 1·10⁻⁷ g for zinc. The results of model experiments and of the analysis of blood taken from two individuals proved to be accurate and reproducible.      

Determination of metals in alloys by neutron capture gamma-ray spectrometry

A collimated neutron beam capable of providing a thermal neutron flux of 4.75·10⁷ n·cm⁻²·sec⁻¹ has been used to analyze alloy samples of 1–5 g during relatively short irradiation times of 30 min by the use of neutron capture gamma-ray spectrometry. The analyses were performed by using a mathematical treatment that relates the count ratio of every constituent present in the matrix with the concentration and thus it requires no standards. The technique was applied to the analysis of steel and gold alloy samples. Errors ranged from 0.8%–10%.     

Investigation of the interaction of Greek dolomitic marble with metal aqueous solutions using rutherford backscattering and X-ray photoelectron spectroscopy

To enhance the applicability of the nuclear analytical technique in the field of industry and the environment, the inorganic elemental content of the bottom ash from a municipal solid waste incinerator was determined by instrumental neutron activation analysis. Bottom ash samples were monthly collected from an incinerator located at a metropolitan city in Korea, strained through a 5 mm sieve, dried by an oven and pulverized by an agate mortar. The samples were irradiated at the NAA #1 irradiation hole (thermal neutron flux: 2.92·10¹³ n·cm⁻²·s⁻¹) in the HANARO research reactor of the Korea Atomic Energy Research Institute and the irradiated samples were measured by a HP Ge gamma-ray spectrometer. Thirty-three elements including As, Cr, Cu, Fe, Mn, Sb and Zn were analyzed by an absolute method. The quality control was conducted by a simultaneous analysis with NIST standard reference materials. The average concentrations of the major elements such as Ca, Fe, Al, Na, Mg, K and Ti measured in the sample were 19.9%, 4.85%, 3.79%, 2.11%, 1.84%, 1.22% and 1.02%, respectively. In addition, the concentrations of the hazardous metals like Zn, Cu, Cr, Sb and As were 0.77%, 0.31%, 729 mg·kg⁻¹, 116 mg·kg⁻¹ and 22.2 mg·kg⁻¹, respectively.     

Analytical use of neutron-capture gamma-rays

Certain elements which are not possible to detect with conventional neutron activation analysis can be measured using thermal neutron-capture gamma-ray analysis. The use of a curved neutron guide at the High Flux Reactor, Grenoble, with a thermal neutron flux of 1.5·10¹⁰n·cm⁻²·sec⁻¹ and the advantage of a low-background counting system (Ge(Li) detector) far from the reactor core are described. Experimental detection limits of a number of elements are given for the low-energy and the high-energy regions. Some applications of the capture gamma-ray method in the whole energy range are studied and are briefly discussed.     

Determination of trace impurities in tin by neutron activation analysis

A method was developed for the determination of 15 trace elements in tin. High-purity tin samples (99.9999% and 99.999%) as well as tin of technical quality were analysed. Reactor neutron activation of the tin samples was followed by distillation of the matrix activities from a HBr−H₂SO₄ medium and Ge(Li) gamma-ray spectrometry of the distillation residue. The sensitivity of the method is generally high. For the high-purity samples the detection limits vary from 0.02 ppb (scandium) to 200 ppb (iron) for irradiation of 1 g of tin for 1 week at a thermal flux of 5·10¹²n·cm⁻². ·sec⁻¹. To decontaminate the surface of the tin samples, pre- and post-irradiation etching procedures were applied. The efficiency of these etching techniques was studied.     

Multi-element analysis of biological samples after intense neutron irradiation an fast chemical separation

For the simultaneous determination of many elements in small biological samples, a multi-element analysis has been developed using neutron activation. After a 24-hr irradiation in a neutron flux of 2.5·10¹⁴ n·cm⁻²·sec⁻¹ and after immediate chemical separation without cooling, it was possible to analyse 24 elements in bovine liver (NBS-SRM 1577). The separation apparatus, set up in a shielded cell can work four samples simultaneously, and its operation is fast enough to allow the detection of radioisotopes with a half-life of about 2 hrs (¹⁶⁵Dy,^57mSr,⁵⁶Mn). Amounts lower than 10⁻³ μg of Dy, Eu, Pr, Sm and Yb were determined.     

Determination of 22 elements in geological samples by instrumental neutron activation analysis

An instrumental neutron activation analysis (INAA) method has been developed for multi-element determination in geological samples. The INAA method consists of irradiation of samples for 90 sec at a flux of 1.0·10¹² n·cm⁻²·sec⁻¹ and determination of 12 elements by using their short-lived nuclides. Samples have been re-irradiated for 3 hrs for measuring concentrations of another 10 elements. Precision and accuracy of the INAA method have been evaluated by analysing samples and USGS standard reference materials. Precision and accuracy are within±15% and ±10%, respectively.     

Characterization of trace elements in medicinal herbs by instrumental neutron activation analysis

Medicinal herbs are often used as alternative medicines for healing and controlling some diseases in the world. This study focuses on the content of heavy and trace elements of some widely consumed herbs in Libya. Nine most popular herbs were analyzed by k ₀-instrumental neutron activation analysis. All the samples, SRM and flux monitors were irradiated for 7 and 10 hours under thermal neutron flux of 1.3·10¹³ cm⁻²·s⁻¹ at Tajoura nuclear reactor. In total, 33 elements were analyzed in different herbs. The variations in the concentration of the elements are attributed to soil composition and the climate in which the plant grows. The study showed that the toxic elements found in the samples were below the levels prescribed by health regulations. The precision and the accuracy of the results were evaluated by analyzing the reference materials Pine Needles SRM 1575 and Citrus Leaves SRM1572.     

The determination of rare earth alloying additives in special steels by neutron activation analysis

A procedure for neutron-activation analysis of cerium, lanthanum, praseodymium and neodymium, tested on more than thirty samples of steels, is described. After irradiation for 20 hrs with a neutron flux of 1.2·10¹³ n·cm⁻²·sec⁻¹ the steel samples were dissolved in aqua regia and extraction separation of iron from 6N HCl by ether was employed. The REE were separated as a group by precipitation as fluorides and hydroxydes. The individual rare-earth elements were separated from each other using a KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutirate as eluant. The separated samples were counted on a NaI(T1) γ-spectrometer.     

Instrumental neutron activation analysis of monomineral fractions of sulfide minerals and quartzes

A method has been worked out of multi-elemental instrumental neutron-activation analysis INAA of small weights some mg of monomineral fractions of sulfide minerals pyrites, galenites, chalcopyrites, arsenopyrites, bornites, chalcosines and quartzes. The samples were irradiated in a nuclear reactor under a flux of 1.3·10¹³ n·cm⁻²·s⁻¹. For measuring the gamma radiation of the exposed samples Ge(Li) gamma-spectrometers with semiconductor detectors were used. Determined in sulfide monofractions were the elements: Co, Sc, Ag, Se, Sb, Cr, Fe, Zr; rare-earth elements: Ce, Sm, Eu and others at content levels of 10⁻¹−10⁻⁴%. In quartzes they were: Mn, Na, Sb, Cr, Sc, Fe, Co at content levels of 10⁻⁵−10⁻⁷% and Au to n×10⁻⁹%. A special method has been worked out for the determination of In in sulfides with the irradiation of samples in a cadmium screen. An example is cited of using the method for studying some peculiar features of the genetics of copper pyrite deposits. The data on the distribution of admixture elements in sulfide monofractions produced in this work made it possible to conclude that the oreformation in the deposits has a stage-by-stage character.     

Radioactivation analysis of aluminium,vanadium, copper,molybdenum, zinc and uranium in natural water samples using organic coprecipitants

A method is described for the determination of trace metal ions, V, Al, Cu, Mo Zn, and U, in natural water samples by neutron activation analysis, using organic coprecipitation as a preconcentration method. The preconcentration of trace elements was accomplished by converting the dissolved trace metal ions into the oxine chelates atpH 5.2 and extraction of the chelates witho-phenylphenol which is a liquid above 56 °C and solidifies at room temperature. After cooling the extraction system, the fine particles of the organic phase were collected on a millipore filter and the precipitate was air-dried in a clean environment. The solid extract was wrapped up in a sheet of clean polyethylene and subjected to neutron irradiation in a reactor for less than 10 min at a thermal flux of 2·10¹³ n·cm⁻²·sec⁻¹. γ-Ray spectrometry by a coaxial Ge(Li) detector connected to a 1024-channel PHA was performed on the irradiated sample without further chemical separation, and thus the ppb level concentration of the elements in natural water samples could be determined. The fundamental study of the collection of the trace elements is also described.     

Gallium determination in biological samples

A sensitive, simple and time-saving method has been developed for the neutron activation analysis of gallium at concentrations around 10⁻⁴ ppm in biological tissues. After a 24-hour irradiation in a thermal neutron flux of 2.8·10¹³ n·cm⁻²·s⁻¹ and a purification by ion-exchange chromatography to eliminate troublesome elements such as sodium, iron and copper, the⁷²Ga activity is measured with enough accuracy for the method to be applicable in animal physiology and clinical toxicology.     

The estimation of barium in biological material by neutron activation analysis

Barium is estimated in biological material by thermal neutron activation analysis and measurement of¹³⁹Ba by γ-counting. The biological material is digested with nitric acid and scavenged with ferric hydroxide. A special fluoride precipitation removes calcium and strontium and the barium is recovered as the chromate. The method allows the analysis of up to 40 samples per day and the sensitivity is 0.1 μg after irradiation for 85 mins at 4·10¹²n·cm⁻²·sec⁻¹.     

Determination of certain elements in human serum albumin by neutron activation analysis

Instrumental activation analysis was used to determine the contents of certain elements in human serum albumin (HSA). Sample irradiation was performed with a thermal neutron flux of 1.5·10¹³ n·cm⁻²·sec⁻¹ in the RA nuclear reactor of the Boris Kidrič Institute, Vinča. Measurements were performed on a 4096-channel analyser with a high-resolution Ge(Li) detector. The Na, Cu, Br, Au, Hg, Cr, Fe, Ag, Sc, Ba and Co contents were determined in HSA produced by the Institute for Blood Transfusion, Belgrade.     

Determination of trace elements in high purity copper by INAA, GFAAS and ICP/AES

Trace impurity elements in high purity copper metal (4 mine class) put on the market were analyzed by Instrumental Neutron Activation Analysis (INAA) and the results compared with those from Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS) and Inductively Coupled Plasma Atomic Emission Spectrophotometry (ICP-AES). The sample irradiation was done at the irradiation facilities (thermal neutron flux, 5·10¹² n·cm⁻²·s⁻¹) of the TRIGA Mark-III research reactor in the Korea Atomic Energy Research Institute. Four unalloyed copper standards (NIST SRM # 393, 394, 395 and 398) were used to identify the accuracy and precision of the analytical procedure. The homogeneity of samples was assessed by means of the elements such as Ag, As, Co, Sb, Se and Zn. The analytical results of INAA, GFAAS and ICP-AES were in good agreement within expected uncertainties each other and showed the possibility of using them for the analytical quality control.     

Activation analysis and autoradiography of impurity distributions in silicon multilayer structures

Activation analysis and autoradiography were used to investigate the concentration distribution of contaminants in poly-Si−Si₃N₄−SiO₂−Si substrate multilayer structures (SNOS) on sampling each technological product. Samples were irradiated for 36 hrs at a thermal neutron flux of 4·10¹³n·cm⁻²·sec⁻¹. The thin films of the analysed sample were removed stepwise by selective chemical etching using appropriate masking techniques. Simultaneously autoradiographs were made of the surface of parallel samples activated under the same conditions. The concentration of the technological contaminants (e.g. Na, Cu, Au) increases in the junction interface of the layers as unambiguously shown by the results obtained. Presented at the “4th Symposium on the Recent Developments in Neutron Activation Analysis” Churchill College, Cambridge, 4–7 August, 1975.     

A technique for the determination of ruthenium stable isotopes in urine samples

Proton activation analysis has been recently applied for the determination of stable isotopes of trace metals in blood plasma samples taken from volunteers during tracer kinetic studies. The very low values of intestinal uptake for some elements, like ruthenium, make the kinetics of the excretion crucial for interpreting the bioassay data. Therefore, a procedure has been developed to process urine samples in order to have proper targets for the activation with protons. Preliminary tests with Ru-doped samples, conducted using the MC-40 Cyclotron at JRC Ispra, has confirmed the feasibility of the method. The minimum detectable concentrations, in the current operating conditions, are 16 ng ⁹⁹Ru^·ml⁻¹ and 0.5 ng ¹⁰¹Ru^·ml⁻¹. On leave from the Federal University of Technology, Akure, Nigeria.     

Evaluation of stray neutron distribution in medical cyclotron vault room by neutron activation analysis approach

Stray neutron distribution in a medical cyclotron vault room was evaluated by neutron activation analysis (NAA). Neutrons were generated in the production of radioactive nuclides, such as ¹⁸F, ¹¹C, ¹³N and ¹⁵O, for diagnostic usage. Indium foil was adopted to evaluate the stray fast and thermal neutron intensity based on ¹¹⁵In(n_f, n′)^115mIn and ¹¹⁵In(n_th, γ)^116m1In reactions, respectively. The indium foils were weighed, sealed and placed at 62 points around the 6.7×8.2 m² cyclotron room. Additionally, each indium foil was exposed for over 80 minutes during cyclotron operation and γ-peaks were analyzed using an HPGe detector to evaluate the number of stray fast (Φ _f) or thermal (Φ _th) neutrons. The minimum to maximum numbers of fast and thermal neutrons were (3.47±0.11)×10³ to (1.06±0.21)×10⁴ n·cm⁻²·s⁻¹ and 9 to 965 n·cm⁻²·s⁻¹, respectively. The minimum detectable limit for stray neutrons was included herein to demonstrate the reliability. Accordingly, 60 and two points, respectively, the confidence level associated with the reported intensities of fast and thermal neutrons reached 95%. The low qualified ratio in the evaluation of stray thermal neutrons might have been caused by either the high Compton scattering plateau or the low intensity of the gamma-ray peak in the relevant spectrum.