Determination of rhenium in molybdenites by neutron activation analysis

A thermal neutron activation method for the determination of rhenium in molybdenites is described. The rhenium is separated from the matrix after irradiation by pyridine extraction from 4 N sodium hydroxide solution; γ- and β-spectrometry are applicable. For a neutron flux of 4 · 10¹¹ n/cm².sec, an irradiation of 2 h and a sample of ca. 50 mg, β-counting allows determinations in the p.p.b. range.     

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 simultaneous determination of rhenium and osmium in rocks by neutron activation analysis

A neutron activation method is described for the determination of rhenium and osmium in rocks. Radiochemical separations, by carrier techniques, are carried out using anion-exchange and solvent extraction procedures. The results obtained for two molybdenites and the standard rocks G-I and W-I are compared with other published values.     

Substoichiometric determination of rhenium in copper ores and molybdenum concentrates by neutron activation analysis

A simple and rapid substoichiometric method is described for the estimation of rhenium in copper ores and molybdenum concentrates by neutron activation analysis. 2 μg of Re can be determined with an accuracy of 4%. The variation of the mean at 95% confidence limit does not exceed 2%. The time required for processing three samples is less than 60 min.     

Determination of iron isotopes by neutron activation analysis

Instrumental neutron activation analysis has been applied to the determination of Fe isotopic abundances in iron materials with the experimental accuracy of 5%. The proposed method can be considered as a quite simple and fast quality check system on the iron isotope enriched oxides used as standard in Mössbauer spectroscopy.     

Determination of lithium by instrumental neutron activation analysis

The fast transfer system in the DR 2 reactor for irradiation at a thermal neutron flux density of 10¹³ n·cm⁻²·sec⁻¹ was used for the determination of lithium by the⁷Li(n, γ)⁸Li reaction. β-counting with a large perspex Cerenkov detector begun at 0.3 s after the end of irradiation, and multi-scaler data was accumulated in 300 channels at 0.1 s per channel. With a suitable choice of discrimination level only¹⁶N and background interfere, and the 0.84 s half-life of⁸Li was resolved by the method of weighted least squares. Results are presented for 36 international geochemical reference materials, and for a few biological samples, including BOWEN's kale and the NBS Standard Reference Material 1571 Orchard Leaves.     

Determination of k-factors by thermal neutron activation technique

The k_{o, Au}-factors of 10 elements have been determined by irradating the samples with thermal neutrons in the reactor thermal column. The proposed method has the advantage of eliminating the errors induced by the uncertainties of the neutron spectrum parameters and the nuclear data. The results obtained are in good agreement with the literature data.     

Determination of gunshot residues by neutron activation analysis

Systematic investigations of gunshot residues, deposited around the bullet hole, have been carried out. The traces were produced by firing on filter papers from distances of 5 to 200 cm using one rifle and three pistols as arms. Antimony, lead and barium were quantitatively determined after irradiating the samples in the nuclear reactor TRIGA Mainz by measurement of gamma-lines of^122mSb,¹²²Sb,^207mPo and¹³⁹Ba. The determinations were made purely instrumentally and-where the half lives were long enough-also after chemical separation of the nuclides. The amount of the elements were determined in dependence of the firing distance and of the area around the bullet hole.     

Determination of gold in platinum by neutron activation analysis

The determination of gold in platinum by neutron activation analysis is described. The possibility of screening out the influence of the nuclear reactions on the final result of the determination was studied. In the case of microamounts of gold in platinum, gold was separated previously by extraction chromatography with dithizone as organic stationary phase. Gold fixed on the column was irradiated and determined gamma-spectrometrically.     

Determination of chromium in blood by neutron activation analysis

A procedure for the determination of chromium in blood has been developed with a sensitivity of 5×10⁻³ μg Cr. Dried blood was irradiated with a neutron flux of 10¹² n·cm⁻²·sec⁻¹ in the VVRS reactor for 4 weeks, then the sample was mineralized and the chromium isolated by extraction as perchromic acid. The determination of the chromium content was accomplished by measuring the 0.32 MeV gamma energy of⁵¹Cr. In order to make correction for the interfering reaction⁵⁴Fe(n,α)⁵¹Cr, the formation of chromium from high-purity iron was investigated. The chromium content of the blood samples was between 1.03×10⁻² and 5.2×10⁻² ppm Cr.     

Determination of some precious metals by neutron activation analysis

A neutron activation procedure for the determination of Ru, Pd, Os, Ir, Pt and Au in a single irradiation in silicate rocks, meteorites and sulfide ores has been developed. An alkali fusion was used to dissolve and mix 100 to 200 mg powder samples with appropriate carriers. The individual metals were separated and brought to a state of high radiochemical purity by distillation, ion exchange and solvent extraction techniques. Precious metal activities were counted by both γ and β-methods. The procedure was evaluated by replicate analyses of the granite and diabase rock standards, G-1 and W-1 and a Cu−Ni sulfide matte which had previously been analysed by emission spectrographic and spectrophotometric methods. The results were compared with previously published data. A major discrepancy was found only for Ir in W-1.     

Determination of bismuth in lead by neutron activation analysis

Neutron activation analysis for bismuth in lead was performed through the separation and measurement of²¹⁰Po, using two different extraction procedures. The reproducibility of the results was good for lead containing bismuth in higher concentrations. For high purity lead, variations in the bismuth content have been found by different analyses of the same sample, owing to inhomogeneity in the distribution of the Bi metal traces. An independent analysis of the same lead samples gave comparable Bi concentrations.     

Determination of molybdenum in biological materials by neutron activation

A method of the determination of molybdenum in biological materials by neutron activation is described. The method is based on the γ-spectrometric measurement of^99mTc after radiochemical separation of the latter by substoichiometric extraction with tetraphenylarsonium chloride using rhenium as inactive carrier. The method has been tested with reference materials.     

Determination of cobalt by substoichiometric thermal neutron activation analysis

A selective method has been developed for the determination of traces of cobalt in different matrices by the sensitive technique of thermal neutron activation analysis employing radiochemical separation and substoichiometric extraction of Co/II/ with iso-nitrosobenzoylacetone into chloroform.     

Determination of thorium in human urine by neutron activation

A routine procedure for the determination of thorium in urine of workers has been developed by the neutron activation method. The technique suggested by Dang, et. al. has been modified in order to reduce the costs involved and the sample processing time. The samples were irradiated in the MIT (Massachusetts Institute of Technology-Boston) reactor, in a thermal neutron flux of 8×10¹²n.cm^–2.s^–1 for 31/2 hours. Thorium-232 was determined by counting²³³Pa.     

Determination of mercury in air by neutron activation analysis

A sensitive method for the determination of mercury in sea and surface waters is presented. A distinction is made between inorganic, organic and particulate mercury. In the determination of inorganic mercury, the element is isolated by reduction and volatilization, followed by absorption on a charcoal column. The total mercury content of the water with and without suspended solids is determined by absorption from the solution onto a column of charcoal. In all cases, the mercury on the absorber is determined by thermal neutron activation analysis. The limit of detection is l ng 1^-1.     

Determination of lithium in graphite by neutron activation analysis

Trace impurities of lithium in graphite is one of the sources of tritium in high-temperature reactors. To determine contents of less then 1ng/g a procedure based on the (n,)-reaction of⁶Li was developed. The samples are irradiated in a reactor and then ignited in a Wickbold apparatus. Thereby the tritium produced by the (n,)-reaction is completely converted in HTO, which can be easily purified by distillation and, if necessary, by a scavenger precipitation step. Several types of graphite have been investigated and the lowest content measured was 0.2 ng/g.     

Determination of mercury in bismuth by neutron activation analysis

A method has been developed for the determination of traces of mercury in bismuth by neutron activation analysis. After sample irradiation at a flux of 7 · 10¹³ n cm^-2 s^-1 for 20 min, mercury was separated from bismuth by addition of ammonium sulfide and re-dissolution of bismuth (matrix) sulfide with nitric acid, and filtration of sulfur containing mercury on a membrane filter. The activity of the 68- or 68–77-keV region, counted with a Ge(Li) or NaI(Tl) detector, was used for quantitative measurements. The method was applied to bismuth samples containing 0.1–100 p.p.m. of mercury.     

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/.