Optimal use of instrumental neutron and photon activation analyses for multielement determinations in sewage sludges

A combination of instrumental neutron activation analysis (INAA) and instrumental photon activation analysis (IPAA) methods has been developed for multielement determinations in a variety of sludges and fertilizers. The precision and accuracy of both the methods have been evaluated by analyzing replicate samples, NBS standard reference materials, and an interlaboratory intercomparison sewage sludge sample. The concentration rages of up to 50 elements in raw and chemical sludges, sludge-based fertilizers, and other organic and inorganic fertilizers are reported here. The advantages and limitations of the INAA and IPAA methods are also discussed here.     

Determination of gold and silver in copper concentrates, using k0 based neutron activation analysis

Procedures for the determination of gold and silver in copper concentrates, using k ₀ based neutron activation analysis, were developed and tested. The effects of gamma-ray self attenuation, neutron self-shielding and spectral interference were considered; precision, accuracy, and detection limits were studied by repeated analysis of copper concentrate internal reference materials. The analytical results have shown good precision and satisfactory accuracy in concordance with the detection limit and range of concentration.     

Performance of NAA Methods in an International Interlaboratory Reference Material Characterization Campaign

An extensive database of analytical results from a recent biological matrix Reference Material Characterization Campaign permitted an intercomparison of the performances of various methods among each other and with "true" best estimate concentration values established for these materials. Six different variants of neutron activation analysis (NAA) methods were employed including: instrumental neutron activation analysis, instrumental neutron activation analysis with acid digestion, neutron activation analysis with radiochemical separation, neutron capture prompt gamma activation analysis, epithermal instrumental neutron activation analysis, and neutron activation analysis with preconcentration. The precision and accuracy performance of NAA-based analytical methods are compared with three other major techniques, atomic absorption spectrometry (AAS), atomic emission spectrometry (AES) and mass spectrometry (MS) for 28 elements in 10 natural matrix materials.     

Polyurethane foam of the polyether type as a solid polymeric extractant for cobalt and iron from thiocyanate media

By combining instrumental and radiochemical neutron activation analysis, up to 47 elements including major, minor, and trace elements, have been determined in lake sediment samples. Instrumental neutron activation involving both short and long irradiations is used to determine 40 elements including most of the environmentally important ones. A radiochemical separation procedure allows the determination of 7 noble metals. The accuracy and precision of the method are 5–10%.     

A critical evaluation of short-lived and long-lived neutron activation products for trace element determinations

The application of short-lived nuclides in routine instrumental neutron activation analysis can reduce total experimental time per sample. The experimental sensitivities of short- and long-lived thermal neutron activation products of 32 elements are compared. The advantages of using short-lived nuclides are evaluated by comparing the precision, accuracy, and detection limits, using both short- and long-lived nuclides, for elemental determinations in biological, environmental and geological standard reference materials.     

Nuclear activation methods for the characterization of fossil fuels

A review is presented on the use of neutron activation analysis (NAA) for the analyses of coal, oil shale, tar sands and petroleum. Fast NAA has been widely used for the determination of oxygen, and to a limited extent, of other elements such as nitrogen and silicon. Reactor NAA followed by instrumental counting, and in specific cases, after radiochemical separations is discussed. Thermal and epithermal neutrons are both used. Limited use of the²⁵²Cf source has been made in fuel analysis. A complementary technique to NAA is the photon-activation analysis with linear accelerator. It can determine over thirty elements, many of them not possible to do by NAA. Round-robin analyses of standard coal, fly ash, or oil shale samples indicate nuclear activation methods are comparable in accuracy and precision to X-ray fluorescence or atomic spectrometric methods for most elements.     

Activation analysis of halogens in photographic emulsions using a252Cf neutron multiplier

A nondestructive neutron activation technique for the simultaneous direct determination of chlorine, bromine, and iodine in silver halide mixtures is described using a²⁵²Cf neutron multiplier (CFX). About 5–50 mg of sample are used. The analysis is semiroutine, without the need for a monitor included with each sample since the flux stability and reproducibility are within ±1%, decaying only with the 2.65 year half-life of²⁵²Cf. The precision and accuracy are counting-statistics controlled and are generally ±1% RSD or better. The method offers an attractive alternative to existing chemical and instrumental methods for these determinations in silver halide mixtures because it has the potential for providing reasonably rapid analyses with good precision and accuracy.     

Neutron activation analysis as a tool for checking the reliability of spectrophotometric methods for the determination of molybdenum and tungsten in biological materials

A new method for the simultaneous determination of molybdenum and tungsten in biological materials by neutron activation analysis has been developed. It involves a single step radiochemical separation of both elements by extraction chromatography using -benzoinoxime supported on Bio-Beads SM 2. Good accuracy and precision of the method was demonstrated analyzing Bowen's Kale and IAEA's H-8 /Horse Kidney/ reference materials. The method was applied to check the reliability of the results obtained by one standard and one newly developed spectrophotometric methods for the molybdenum content in some plant materials.     

Scalp hair as a monitor of population exposure to environmental pollutants

Concentrations of As, Cd, Hg, Pb, Sb and Zn have been measured in hair from population groups with varied types of environmental exposure. Rural and urban controls have exhibited low levels of most toxic elements, whereas people residing near urban lead refineries, rural gold refinery and other industries have shown high elemental concentrations in their hair. A combination of instrumental as well as radiochemical neutron and photon activation analysis methods have been used to determine the concentrations of the above elements. The precision and accuracy of these methods have been evaluated.     

Determination of arsenic and bromine in hot spring waters by neutron activation analysis

Concentrations of arsenic and bromine dissolved in hot spring waters have been determined by neutron activation analysis using 0.5 cm³ of sample waters without any chemical pretreatment. The samples prepared for neutron irradiation were simply pieces of filter papers which were infiltrated with samples. With the results of satisfactorily high accuracy and precision, this analytical method was found to be very convenient for the determinations of arsenic and bromine dissolved in water at ppm to sub-ppm levels.This revised version was published online in November 2005 with corrections to the Cover Date.     

On the origin of some red soils from Sardinia (Italy): A neutron activation analysis investigation

In Sardinia, the Italian island in the middle of the MediterraneanSea, there are many red soils developed on limestone or dolomite. Soil andunderlying bedrock samples from 5 different sites have been submitted to chemicaland mineralogical characterization, by using standard X-ray diffraction analysis,spectrochemical methods and instrumental neutron activation analysis. Obtainedresults are presented and discussed in terms of precision and accuracy. Traceelement concentration variation with depth is discussed as well as the enrichment/depletionratios between soils and rocks, and the rare-earth element distribution. Dataanalysis suggests for some soils a formation process based on the evolutionof the underlying bedrock, and for the other soils a formation process partlybased on the evolution of the local rock but with meaningful contributionsof external sources, both eolian and/or alluvial.     

Destructive and nondestructive analysis of some elements in tissue and environmental samples by thermal neutron activation analysis technique

A rapid and selective method has been developed and applied for determining elements present in tissue and environmental samples by both destructive and nondestructive activation analysis. Nondestructive activation analysis involves the irradiation of the sample and standard of the elements such as Mn, Na, and K with thermal neutrons from²⁵²Cf neutron source followed by radioassay of the (n,r) products on a HPGe detector coupled to a PC-based MCA. Elements are determined by irradiating the samples in the thermal neutron flux of the CIRUS reactor and radiochemically separating the isotopes of interest using substoichiometric extraction and precipitation technique. The statistical evaluation of the method with respect to accuracy and precision of the method and its sensitivity are discussed.     

The determination of uranium in biological materials by neutron activation analysis using the fission product134I

A method for the determination of uranium based on²³⁵U thermal neutron fission, has been developed and employed on samples of ashed fish tissue and seaweed. The method involves a post-irradiation ion exchange separation of iodine isotopes. The 884 keV photopeak of¹³⁴I is used for measurement. Uranium detection limits in the samples concerned have been estimated to be 1·10⁻⁸g in terms of natural uranium. The precision achieved in analysing several series of 3–5 samples was 4–10 per cent. The accuracy of the method was tested by employing an independent neutron activation procedure based on²³⁹U measurement. The accuracy of both methods was checked by analysing NBS SRM 1571 ‘Orchard Leaves’.     

Determination of tungsten in ores by X-ray fluorescence technique and X-rays in neutron activation analysis

Two distinct analytical methods have been described for analysis of W in tungsten ores. For the proposed study, thick and thin samples were analyzed by using X-ray fluorescence technique with great accuracy. Standard comparison method is based on the measurement of K line for tungsten. Also, W has been determined in similar ore samples by neutron activation analysis followed by X-ray spectrometry employing a²³⁸Pu-Be neutron source. The measured Re K-X rays are emitted in internal conversion of¹³⁷W produced during thermal neutron activation.     

Contribution to the characterization of reference materials for thin-film analysis in solar-energy and semiconductor technologies

A combined approach of independent surface and bulk analytical methods was applied to characterize materials that had been prepared by ion implantation of P. Co and Ni ions into high purity silicon, for use as reference materials in thin-film analysis techniques. In this characterization, high precision and accuracy of 1–2% were obtained by utilizing instrumental neutron activation analysis for the determination of the total implanted ion dose. The impact of the analytical results on the preparation procedure is discussed.     

Comparison of neutron activation analysis methods

This work shows that nuclear data and neutron flux parameters can be applied to calculate directly the elemental concentrations. Techniques for extracting neutron flux parameters pertaining to the irradiation positions and nuclear data pertaining to the isotopes concerned from measured reaction rates have been previously developed. This method is compared to the comparator and relative methods of activation analysis. The principles, advantages and disadvantages of each method and sources of errors are discussed. It also briefly discusses other factors such as accuracy and precision, sensitivity, detection limits and limit of quantitative determination. The three methods are applied to the analysis of five environmental reference materials. The concentrations of more than 20 elements are determined. The results show a good agreement with the certified and/or literature values.     

Evaluation of methods for the assay of neptunium and other long-lived actinides in environmental matrices

Inductively coupled plasma mass spectrometry (ICP-MS) and neutron activation analysis (NAA) have been investigated as alternatives to alpha-spectrometry for the low-level determination of²³⁷Np and other actinides in environmental matrices. ICP-MS in particular, has been shown here to offer suitable sensitivity, precision and accuracy compared to the other techniques, with considerably faster sample throughput relative to radiometric and activation approaches. Added advantages of ICP-MS are found to include the abilities to determine other long-lived actinides simultaneously and to quantify²³⁹Pu:²⁴⁰Pu ratios. The neutron activation analysis approach was found to be particularly prone to interference especially from uranium nuclides.     

Characterization of InxGa1−xAs crystals by 14 MeV neutron activation analysis

Indium doped GaAs crystals are analyzed quantitatively for indium by non-destructive 14 MeV neutron activation analysis. Experimental conditions are optimized to provide a precision of ±5% and a practical sensitivity of 50 ppm, by weight. The accuracy of the neutron activation method is established by comparison with the results obtained by atomic absorption and Rutherford back-scattering techniques. The method has been applied for determining the homogeneity of indium distribution of wafers by sectional analysis and is demonstrated as a reference method for calibrating the low temperature photoluminescence technique.     

Substoichiometric extraction of metals and its application to the determination of heavy metals in environmental samples by neutron activation analysis

Solvent extraction as a technique for the separation of ionic solutes and the advantages and application of substoichiometric extraction in neutron activation analysis have been discussed. The application of this technique has been elucidated with reference to the determination of Zn, Cd and Hg in environmental samples. The decontamination factor, accuracy, precision, sensitivity and radiochemical purity of the separated fraction have been discussed.     

Application of NAA standardization methods using a low power research reactor

Two widely used neutron activation analysis (NAA) standardization methods (relative and k ₀) have been validated at the Ghana Research Reactor-1 (GHARR-1) Centre using environmental and biological standard reference materials (SRMs). The samples were IAEA Soil-7 as an environmental sample, and NIST Orchard Leaves 1571 as a biological sample. The qualitative and quantitative analyses were done using a high resolution Canberra N-type high purity germanium (HPGe) detector. The accuracy and precision were evaluated for the elements analysed. The concentrations of most of the elements were found to be within 10% of the certified values. Precision was calculated from six replicate measurements and was found to be within 15%.