Progress in neutron activation analysis for uranium

A new type of extractant, sym-dibenzo-16-crown-5-oxyhydroxamic acid (HL) is introduced. The extractions of UO22+, Na+, K+, Sr2+, Ba2+ and Br- were studied with HL in chloroform. The results obtained show that UO22+ can be quantitatively extracted at pH values above 5, whereas the extractions of K+, Na+, Sr2+, Ba2+ and Br- are negligible in the pH range of 2 - 7. The dependence of the distribution ratio of U(VI) on both the concentration of the HL and pH are linear, and they have the same slope of 2. This suggests that U(VI) appears to form a 1:2 complex with ligand. Uranium(VI) can be selectively separated and concentrated from interfering elements such as Na, K, Sr and Br by solvent extraction with HL under specific conditions. The recovery of uranium is nearly 100% and the radionudear purity of uranium is greater than 99.99%. Therefore, neutron activation analysis has greatly improved the sensitivity and accuracy for the detection of trace uranium from seawater.     

The program “MULTINAA” for various standardization methods in neutron activation analysis

A compute program MULTINAA was developed to facilitate the evaluation of NAA data. It is written for the VAX/VMS syste and opeates in the Canberra/ND Genie spectroscopy software environment. MULTIINAA can be appliede to relative,k ₀-, monostandard (modified) and absolute methods, including the fast neutron threshold reaction. For each calculation, the available standardizations can be used individually or mixed. In all the standardization modes MULTINAA fetches the data directly from the -ray spectra and libraries, thus reducing the manual work to a minimum. MULTINAA is flexibkle to meet various situations in NAA practical work. The required neutron flux parameters all the non-relative methods are supplied by an accompanying program MULTIFLUX.     

Oxygen isotope measurement by instrumental neutron activation analysis using reactor neutron—Revisited

The oxygen isotopes¹⁶O and¹⁸O were determined using reactor instrumental neutron activation analysis by utilizing the¹⁶O(n, p)¹⁶N and the¹⁸O(n, )¹⁹O reaction in the UCI 250 kw TRIGA research reactor.¹ Such measurements were used to follow an exchange reaction between H₂ ¹⁸O and finely ground coal. The best conditions for the determination were explored and interference reactions quantified. Single irradiation/count sequences were used to determine 30 parts per thounsand of¹⁶O and 1 part per thousand of¹⁸O in a 400 mg sample of an HVA rank coal to a 25% (1) precision. Reactor pulses were shown to improve these detection limits significantly. Special attention was given to correcting for the high count rates from other induced activites.     

Multielement analysis of foods by neutron capture prompt γ-ray activation analysis

A method is described for the determination of H, B, Cl, K, Na, S, Ca, and Cd in foods using in-beam neutron capture prompt -ray activation analysis. Special calibration procedures were necessary because of matrix-related thermal neutron scattering-induced sensitivity and background enhancements. Detection limits and sensitivities are presented for best-case and worst-case irradiation conditions. The method was applied to multielement analysis of 41 foods and to B, Cl, and K analysis of 13 orange juice produts in conjunction with analysis by inductively coupled plasma atomic emission spectrometry. The purpose of the latter application was to study B losses during acid digestion.     

Cold neutron prompt gamma-ray activation analysis at NIST — Recent developments

The cold neutron capture prompt -ray activation analysis (CNPGAA) spectrometer located in the Cold Neutron Research Facility (CNRF) at NIST has proven useful for the analysis of hydrogen and other elements in a wide variety of materials. Modifications of the instrument and the CNRF have resulted in improved measurement capabilities for PGAA. The addition of an atmosphere-controlled sample chamber and Compton suppression have reduced -ray background and increased signal-to-noise ratio. More recent revisions are expected to yield still further improvement in analytical capabilities. Replacement of the D₂O ice cold source with a liquid H₂ moderator is expected to yield a 5–10 fold increase in neutron capture rate, and improved neutron and -ray shielding will result in further reduction of the background. Other modifications to the instrument allow easier sample mounting and more precise positioning of samples in the neutron beam. Significant improvements in detection limits and analytical accuracy are expected.     

Determination of As by instrumental neutron activation analysis in sectioned hair samples for forensic purposes: chronic or acute poisoning?

Autopsy of 29-year old woman suspicious of committing suicide by the ingestion of As₂O₃ yielded contradictory findings. All pathological findings as well as clinical symptoms suggested acute poisoning, while a highly elevated As level of 26.4 μg g⁻¹ in her hair collected at the autopsy, which was determined with inductively coupled plasma mass spectrometry indicated chronic poisoning. To elucidate this discrepancy, instrumental neutron activation analysis (INAA) with proven accuracy was performed of another set of sectioned hair samples. Levels of As found by INAA in the range of 0.16–0.26 μg g⁻¹ excluded chronic poisoning, because the person died after approximately 14 h after the As₂O₃ ingestion. Two reasons for the discordant As results obtained by ICP-MS and INAA are considered: (1) accidental, non-removed contamination of hair on the As₂O₃ ingestion; (2) erroneous performance of ICP-MS.     

A preliminary assessment of the provenance of ancient pottery through instrumental neutron activation analysis at the Monte Castelo site,Rondônia,Brazil

Journal of Radioanalytical and Nuclear Chemistry - This research aims to contribute to the discussion of ceramic objects found at the Monte Castelo shellmound, an archaeological site located at...     

An241Am−Be source based thermal neutron activation analysis facility at KFUPM

An instrumental thermal neutron activation analysis facility based, on a 16 Ci²⁴¹ Am–Be source, a high resolution -ray spectrometry setup and a PC-based data acquisition system at KFUPM is described. The thermal neutron flux distribution was determined from the induced activities of high purity indium foils. The absolute thermal neutron flux was calculated from the activities of bare and cadmium-covered gold foils at a position of 3 cm from the soource at which the flux reaches a maximum. The facility tests were carried out with the determination of manganese concentrations in six types of industrially important steel samples. The result of 1.33% manganese in SS-304 steel sample was in excellent agreement with the literature value. The method is nondestructive, economical and ideal for bulk analysis.     

Miniaturization through lab-on-a-chip: Utopia or reality for routine laboratories? A review

Micro total analysis (μTAS), also called “lab-on-a-chip (LOC)” technology, promises solutions for high throughput and highly specific analysis for chemistry, biology and medicine, while consuming only tiny amounts of samples, reactants and space. This article reports selected contributions of LOC, which represent clear practical approaches for routine work, or presenting potentiality to be transferred to routine analytical laboratories. Taking into account the present LOC state-of-the-art, we identify various reasons for its scarce implementation in routine analytical laboratories despite its high analytical potential, as well as the probably main “niche” for successfully practical developments is suggested.     

Use of neutron activation analysis and LC–ICP-MS in the development of candidate reference materials for As species determination

Arsenic (As) is widely found in marine organisms, mainly as organic arsenical compounds. With the introduction of regulations for As species in foodstuffs and for environmental control, it has become more important to quantify the amount of arsenic species present. To address this concern new reference materials (RMs) for validation and quality assurance of As speciation measurements are being developed, including a tuna fish tissue and a robalo liver tissue. Instrumental neutron activation analysis (INAA) is used in this work as a proven analytical tool for As determinations and for validating the As mass fraction determined by liquid chromatography coupled to inductively coupled mass spectrometry (LC–ICP-MS) in extracts of the candidate RMs and other fish samples including certified RMs. Various methods for the extraction of water-soluble As species were evaluated. The best results were acquired after methanol/acetone/water extraction yielding in 93 % extractable As in the tuna RM. This procedure was used for the LC–ICP-MS studies. The results demonstrate that INAA can account for 100 % of the distribution of As species in analytical processes. It complements LC–ICP-MS for the validation of the characterization of As species in the development of RMs for such species. Excellent agreement of measured results in certified RMs with the reported values confirms the validity of the applied procedures.     

Thorium determination in a liver autopsy sample via direct γ-spectrometry and neutron activation analysis

Thorium was determined in a liver autopsy sample from a person treated with Thorotrast ca. 40 y earlier. The decay products²²⁸Ac,²²⁴Ra,²¹²Pb,²¹²Bi, and²⁰⁸Tl from the²³²Th series were identified by direct -spectrometry. Instrumental neutron activation analysis yielded a value of ca 22 g thorium per kg dry liver material. The total radiation dose to the whole liver was estimated in the order of 16 Gy.     

Some studies on the formulation of “Khun-hnit-par-shaung” Myanmar indigenous medicine by neutron activation analysis

A study on the variation of arsenic content in Khun-hnit-par-shaung indigenous medicine formulated under various experimental conditions such as heating interval, sand amount and heating temperature has been carried out. An Am(Be) neutron source was used for the activation of samples and⁷⁶As was radoactivity measured by a -counting technique.     

Can instrumental neutron activation analysis keep pacewith the needs of the high purity materials industry?

The University of Missouri Research Reactor Center (MURR) has been one of the premier providers of neutron activation analysis (NAA) to the high purity materials industry for the past 20 years. Over the last two decades, significant advances in contamination control in the manufacturing process and the development of alternate analytical techniques have challenged the NAA community to keep pace. This paper presents an overview of the High Purity Materials Analysis Program at MURR. Specifically we present trends in the trace element concentrations that we have observed in our laboratory over the past 10 years and compare our experience with the relevant literature. The prospects for the future success of NAA and the methodological changes required for satisfying the industry's need will be discussed.     

A new principle of activation analysis separations—I: Theory of substoichiometric determinations

Separation procedures in the activation analysis of elements mainly consist of many steps which are usually derived from classical analysis schemes. In all cases an excess of reagent (precipitating, complexing, etc.) is used for separation of the element to be determined. In the present paper separations by means of a smaller amount of reagent than corresponds to the stoichiometric ratio of element to be determined are discussed. The use of an insufficient amount of the reagent has two advantages : greater selectivity (possibility of eliminating many steps) and elimination of the necessity for determining the chemical yield of the element in question. As a result the analysis is more rapid.