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 the silver content of ancient silver coins by neutron activation analysis

A reactor neutron activation analysis procedure for the determination of the silver content of silver coins is described. The samples are irradiated for 1 s, cooled for 85 s and measured for 60 s with a Ge-detector. The analysis is based on the measurement of¹¹⁰Ag and¹⁰⁸Ag. Aluminium is used for flux monitoring and pulse pile-up correction. A calibration curve is prepared by irradiating and measureing a series of discs with known silver contents. An average precision of ±2.1% is obtained. The analysis of coins with known silver contents shows good agreement with the given values. The analysis time is 2.5 minutes per sample.     

Physico-chemical characterization and thermal analysis data of alumina waste from Bayer process

In the aluminum industries, there are several steps involved in processing since the extraction of bauxite to obtain the final product (Al). During the development of these, various steps generated wastes. One of them, from the electrostatic filter of the calcination step of the Bayer process is a very fine black powder, rich in alumina (Al₂O₃) that does not meet industry specifications, and it is discarded in the industry yard. Alumina is a noble material and has high commercial value. This black powder has great prospects for recovery, recycling, and future applications. Therefore, it is important to perform characterization of tailings and to do that we have used XRD, SEM, EDS, FTIR, Raman, and thermal analysis.     

Determination of silicon in iron by thermal neutron activation

A new chemical separation procedure for the determination of silicon in iron after neutron activation was developed. It uses two separation steps, one on a cation exchange resin in HCl−HF-acetone medium, and the other on alumina at pH 9. The detection limit for silicon was 0.02 μg. This analytical procedure was applied to the control of the zone-melting purification of iron.     

Study of Pt-Re/alumina reforming catalysts by neutron activation analysis

The elemental analysis of Pt-Re/alumina catalysts was carried out by nondestructive and bulk neutron activation analysis. Samples were irradiated with a²⁴¹Am-Be source-based as well as accelerator-based thermal neutrons and induced activities were measured by a HPGe detector with a PC-based data acquisition and analysis system. An appropriate calibration technique was established for the determination of the respective ratios of each element present in the catalysts. The technique proved to be useful for the determination of low concentrations of Pt and Re in the catalyst samples.     

Multielement content of coal by neutron activation analysis techniques

Due to the interaction with components present in natural waters, radionuclides may be present in different physico-chemical forms, varying in size, charge and density. The distribution pattern will influence the transport, mobility and biological uptake of the radionuclides. Size fractionation based on hollow fiber is useful for the determination of the size distribution pattern of radionuclides in natural waters. Furthermore, a continuous mixing and separation system has been developed for the investigation of the association of radionuclides with naturally occurring colloids. Results based on radionuclides in waste water from the Forsmark nuclear power plant, Sweden, will illustrate the potential usefulness of the technique.     

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 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 chromium, iron and cobalt in high-purity niobium by radiochemical neutron activation analysis

Summary Chromium, iron and cobalt were determined in niobium by radiochemical neutron activation analysis. The main steps of the technique involved the irradiation of the samples in a medium or high-flux reactor, the post-irradiation decontamination of the sample surface, a two-step separation procedure based on anion-exchange from HF and HCl medium, and counting the separated indicator radionuclides with a well-type NaI-detector. For a 42-day irradiation at a thermal neutron flux of 8×10¹³ n cm^–2 s^–1 and a sample weight of 100 mg, the limits of detection are: 10 ppt for chromium, 1.5 ppb for iron and 4 ppt for cobalt. The results obtained by this technique are compared with data obtained by radiochemical proton activation analysis and atomic absorption spectrometry.

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Bestimmung von Chrom, Eisen und Cobalt in hochreinem Niob durch radiochemische Neutronenaktivierungsanalyse

Zusammenfassung Die Hauptschritte der Methode sind die Bestrahlung der Probe in einem Mittel- oder Hochflußreaktor, eine anschließende Oberflächendekontamination und die spezifische Abtrennung der Indicatorradionuklide mittels Anionaustausch aus Flußsäure- und Salzsäure-Medium, sowie die Messung der Radionuklid-Fraktionen mit einem Natriumjodid-Detektor.Für eine 42tägige Bestrahlung mit Reaktorneutronen bei einem thermischen Fluß von 8×10¹³ n cm^–2 s^–1 konnte bei einem Probengewicht von 100 mg für Chrom eine Nachweisgrenze von 10 ppt, für Eisen von 1,5 ppb und für Cobalt von 4 ppt erreicht werden.Die mit dem Verfahren erhaltenen Ergebnisse werden mit denen der radiochemischen Protonenaktivierungsanalyse und der Atomabsorptions-Spektrometrie verglichen.

     

A review of the determination of organic compounds in Bayer process liquors

Bayer process liquors present a difficult and complex matrix to the analytical chemist, and the history of the application of modern analytical techniques to this problem is a case study in innovation. All Bayer process liquors contain organic compounds, in amounts varying from traces to several grams per litre. The total organic carbon content of Bayer liquors may be less than 5 g/L up to as much as 40 g/L. The presence of these organic impurities is of concern to Bayer technologists because they can have significant impacts on the economics of the process and the quality of the product. This review examines the history and current state-of-the-art of the analysis of organics in Bayer process liquors, and provides guidance on the applicable techniques matched to a comprehensive list of the compounds most likely to be present.     

Determination of silicon in cast iron by 14 MeV neutron activation

Silicon in cast iron was analyzed by 14 MeV neutron activation—high-resolution γ-ray spectrometry. Silicon was detected as²⁸Al, the product of the²⁸Si(n, p)²⁸Al reaction. Interference of⁵⁶Mn was separated using a Ge(Li) detector and a biased amplifying system. The 1. 81 MeV gamma-radiation of⁵⁶Mn, which is the product of the⁵⁶Fe(n, p)⁵⁶Mn reaction of the matrix of cast iron, was used as an internal standard and for correction of the self-absorption of the 1. 78 MeV gamma-radiation of²⁸Al by the sample. The interferences of aluminum, phosphorus and manganese could be neglected according to the results calculated from their nuclear properties and contents in the cast iron of this experiment. The results of this method agreed well with the results of the usual chemical method, with errors less than 5% of the results, and the precision of the method was satisfactory with a C. V. of less than almost 6% for rapid analysis of silicon in cast iron. The analytical line through the origin with a slope of the mean value of the repetition experiments could be used as the analytical line with almost the same precision and accuracy of the results as for the analytical line calculated by the least squares method.     

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 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 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 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.     

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 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.