Multielement characterization of silicon carbide powders by instrumental neutron activation analysis and ICP-atomic emission spectrometry

Summary Instrumental neutron activation analysis (INAA) and inductively coupled plasma atomic emission spectrometry (ICP-AES) have been optimized for application to a comprehensive analysis of silicon carbide powders. Via medium- and long-lived indicator radionuclides with half lives between 2.3 h (¹⁶⁵Dy) and 12.4 a (¹⁵²Eu), INAA can detect 55 elements. Analytical parameters and experimental modes are given with limits of detection obtained for a silicon carbide powder of typical purity grade. For the performance of ICP-AES, a wet-chemical decomposition procedure was optimized for sample portions of about 1 g using a mixture of high-purity conc. HF, HNO₃ and H₂SO₄ for digestion in autoclaves with a PTFE-liner. For all investigated elements, recoveries 98% were obtained. By scanning wavelength profiles, interference-free emission lines were found for 56 elements. By the combined performance of INAA and ICP-AES, 66 elements were assayed in the analysed silicon carbide powder. The limits of detection were below 0.01 g/g for 24 elements, they were between 0.01 and 0.1 g/g for 17 and between 0.1 and 1 g/g for 15 elements. The remaining 10 elements were detectable at levels >1 g/g. The comparison of results of these two methods as well as of results obtained by other laboratories shows that, for the most common impurities, a satisfactory degree of accuracy could be achieved.     

A comparison of INAA and ICP-MS/ICP-AES methods for the analysis of meteorite samples

Instrumental neutron activation analysis (INAA), inductively coupled plasma atomic emission spectrometry (ICP-AES) and ICP mass spectrometry (ICP-MS) (hereafter, ICPs) were applied to meteorite samples for the determination of elemental content. The analytical applicability and suitability of the three methods have been compared. Those comparisons led to the refinement of our analytical procedures for INAA and ICPs, yielding more reliable data. Our INAA data proved to be reliable enough for classifying meteorites, while the ICPs, especially ICP-MS, can characterize elemental abundance features in detail, as demonstrated by REE abundance patterns for the Allende meteorite. In this manner, INAA and ICPs can be used in a complementary fashion in cosmochemical studies.     

Analytical procedure for the determination of thorium, zinc and potassium in diet samples

Instrumental neutron activation analysis (INAA), and atomic absorption spectrometry (AAS) have been used for the determination of trace amounts of thorium, zinc, and potassium in diet samples. Interlaboratory comparison has been made. The z-scores show that INAA can be used to determine thorium and zinc whereas AAS can be employed to determine potassium in diet samples.     

Distribution and speciation of selenium in Lecythis ollaria plant

Selenium has been determined in different parts of the Lecythis ollaria (LO) plant (Venezuela) and the determination of its speciation has been achieved in fruit seeds. The study has been performed using different analytical techniques including inductively coupled plasma atomic emission spectrometry (ICP-AES), differential pulse cathodic stripping voltammetry (DPCSV), instrumental neutron activation analysis (INAA), high performance liquid chromatography (HPLC) and mass spectrometry (MS). Different parts of the plant (leaves, bark, capsules and seeds) were examined as well as the soil where LO was growing. Among different considered parts, seeds show the highest content in selenium (5 g kg⁻¹) which is dependent on the maturation extent of the fruit. In seeds, about half of the total selenium content is soluble in water while the remaining is involved in protein structure. In the aqueous fraction, the prevailing form of selenium appears to be seleno-cystathionine with much lower amounts of Se(VI) and Se(IV).     

Multielement analytical procedure coupling INAA, ICP-MS and ICP-AES: Application to the determination of major and trace elements in sediment samples of the Bouregreg river (Morocco)

Instrumental neutron activation analysis (INAA), inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) were used for the determination of major and trace elements in sediment samples of the Bouregreg river (Morocco). The reliability of the results was checked, by using IAEA Soil-7 certified reference material. Results obtained by the three techniques were compared to control digestions efficiencies. A general good agreement was found between INAA and both ICP-MS and ICP-AES after alkaline fusion (ICPf). The ICP-MS technique used after acid attack (ICPa) was satisfactory for a few elements. A principal component analysis (PCA) has been used for analyzing the variability of concentrations, and defining the most influential sites with respect to the general variation trends. Three groups of elements could be distinguished. For these groups a normalization of concentrations to the central element concentration (that means Mn, Si or Al) is proposed.     

Large-sample neutron activation analysis: Present status and prospects

Neutron activation analysis is attractive for trace-element determinations in large samples. Facilities for reactor irradiation and -ray spectrometry of kilogram-size cylindrical samples are described. The thermal neutron flux is ca. 5·10¹²m^–2·s^–1 with a _th/ _epi>10⁴, so neutron self-thermalization can be neglected. The correction for the neutron attenuation within the sample is derived from measurement of the neutron flux depression just outside the sample. Correction for -attenuation in the sample is performed via linear attenuation coefficients derived via transmission measurements. Also the natural radioactivity in the sample is taken into account. Examples are given of materials to which large sample INAA has been applied successfully, and further lines of development and exploration are indicated.     

Speciation of Se, Fe and Zn in Human Milk Whey: The use of Instrumental Neutron Activation Analysis (INAA) to corroborate element profiles measured with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)

In human milk trace elements normally exist in a form which can easily be absorbed by the newborn infant. For investigations of the bioavailability of trace elements it is necessary to carry out a speciation analysis of the elements of interest. An independent analytical method has been used for the quality control of the shape of the element profiles obtained from the speciation analysis of Se, Fe and Zn in individual samples to human milk whey after chromatographic separation. For the element detection in the untreated milk fractions Instrumental Neutron Activation Analysis (INAA) was chosen as the reference method. Element distribution patterns have been obtained with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) using on-line digestion of the fraction, reduction and hydride formation of Se (T-mode). Prior results are compared with those obtained by means of element detection in the untreated fractions (U-mode) with ICP-AES. The elution profiles of Se, Fe and Zn in human milk whey obtained by means of ICP-AES detection using the T-mode show good agreement with the distribution patterns obtained with INAA. Recoveries of 103% for Fe, 86% for Zn and 87% for Se were obtained. The element distribution patterns of Fe and Zn obtained with ICP-AES speciation using the T-mode also show good agreement with those obtained by means of ICP-AES using the U-mode.Dedicated to Professor Dr. Peter Brätter on the occasion of his 60th birthday.     

Comparison of routine INAA procedures based on k0 and kZn standardizations

Performance characteristics (especially accuracy) of a routine INAA with k₀ standardization were verified and compared with those of INAA with a classical single comparator. For this purpose, samples of three certified reference materials of environmental origin (Fly Ash, Orchard Leaves and Buffalo River Sediment—all supplied by NIST) were irradiated with both kinds of comparators (Au–Zr for k₀ and Zn for classical k method) in one irradiation rabbit. Also the following steps of INAA procedure were practically the same for both standardization methods used (counting, spectral processing, etc.). The results have shown that the k₀ method gives sufficiently accurate results comparable with those of the well established and routinely used single comparator (Zn) method, provided proper neutron flux monitoring, efficiency calibration and also coincidence summing corrections are applied. This work shows that modern k₀ standardization method in INAA can be sucessfully used in routine practice and applied with an advantage in INAA laboratories subject to changes of neutron spectra or counting conditions.     

Quality Control in Element Analysis of Plant Materials

A worldwide laboratory intercomparison was organized by the International Atomic Energy Agency's Analytical Quality Control Services (AQCS) involving the determination of elements in plant materials used for human consumption. The main purpose of this work was to evaluate the performance of our analytical methods including sample preparation and to obtain new reference materials that can be used in our further work. Both materials (spinach and cabbage) were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES) and instrumental neutron activation analysis (INAA). Six subsamples of each material were subjected to our digestion procedure and the solutions were measured by ICP-AES. The dried samples were analyzed using INAA. Up to 26 elements were determined in plant materials. For easy review of our data a score has been calculated based on the reference value for each measured element. According to our results the ICP-AES technique was useful for determination of the following elements: Ba, Ca, Cr, Fe, K, Mn, Mo, P, S, Sr, Ti. The INAA method was reliable for measurement of Ce, Co, Mn, Na, Rb, Th, and V.     

Examination of steel samples, provided as reference materials, by instrumental analyses

Summary Seven steel samples considered as reference materials have been analysed by atomic emission spectrometry with inductively coupled plasma (ICP-AES), atomic absorption spectrometry with flame and graphite furnace atomization (FAAS, GFAAS), differential pulse anodic stripping voltammetry (DPASV), X-ray fluorescence analysis with total reflection sample carrier (TXRF), and instrumental neutron activation analysis (INAA). Totally, 18 elements were determined. Over 90% of all results were in good agreement with the values determined by wet analytical methods. The deviations can be explained by systematical errors for special elements in distinct methods and by statistical errors, mainly at very low concentrations because some elements, in the low ng/g region, are not homogeneously distributed in the given material.formerly: Amt für Standardisierung, Meßwesen und Warenprüfung, Große Steinernetischstrasse 4, DDR-3010 Magdeburg     

Vanadium levels in marine organisms of Onagawa Bay in Japan

Vanadium in marine organisms from Onagawa Bay in Miyagi, Japan, was determined by an instrumental neutron activation analysis (INAA) method using anti-coincidence gamma-ray spectrometry at the Dalhousie University SLOWPOKE-2 Reactor (DUSR) facility in Canada. Seaweeds, cultivated oysters, plankton, and four different species of sea squirt were collected from Onagawa Bay during 2005–2008. Vanadium levels around 20 μg g⁻¹ (dry weight) were found in Japanese tangle and hijiki seaweeds. One species of sea squirt (Ciona savignyi) contained 160–500 ppm of V and it was highest among the four species of sea squirts studied. Protein-bound V species were separated by gel permeation chromatography (GPC) and the element determined by inductively coupled plasma atomic emission spectrometry (ICP-AES).     

Nuclear analytical techniques for quantification of uranium for its recovery from seawater

Nuclear analytical techniques namely fission track technique using solid state nuclear track detector (SSNTD) and instrumental neutron activation analysis (INAA) have been standardized and applied for quantification of low uranium concentrations in liquid samples such as feed, elute and brine and solid sorbent samples respectively. The quantification of uranium is required for its recovery study from seawater, which is one of the potential sources of uranium. The uranium concentration of a liquid sample obtained by SSNTD method was compared with the other well established conventional techniques like ICP-MS, ICP-AES, adsorptive stripping voltametry and alpha spectrometry. INAA was applied for uranium concentration determination in the radiation grafted polyamidoxime sorbent samples.     

Characterization of high-purity aluminium

Summary The state of the art in characterization of high-purity aluminium, including activation analysis, glow discharge mass spectrometry (GDMS) and wet chemical multistep procedures has been described. It has been shown on the basis of comparative tests, in which laboratories in Europe, Japan and USA have participated, that with regard to power of detection as well as reproducibility even at levels below 500 ng/g neutron activation analysis (INAA, RNAA), wet chemical multistep procedures and GDMS can contribute to the characterization of high-purity aluminium. The measurement of the resistivity ratio have proved as a suitable test for the integral content of dissolved impurities. H at levels of 0.3 g/g can be measured by vacuum solid extraction or carrier gas fusion. For a complete and optimal characterization of high-purity aluminium all these methods are needed and should periodically be checked against each other.

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Charakterisierung von hochreinem Aluminium

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Thanks are expressed to VAW High-Purity Metal Division for allowing of publishing the foregoing results and financial support.     

Decreasing the detection limits to ppq levels for high purity silicon analysis by instrumental neutron activation analysis with kilogram sampling weight

The amount of silicon sample used in instrumental neutron activation analysis (INAA) is generally less than twenty grams and the detection limits are in the range of ppb to ppt. The detection limits can be decreased further in several ways. Increasing neutron flux density, extending irradiation period and/or using more effective detector can improve the detection limits to some extent. Increasing sample weight, however, is a more feasible way to decrease the detection limits by a factor of hundreds with no new investment in existing irradiation/counting systems. In this work, two 8-inch high-purity silicon samples were analyzed by INAA to evaluate the validity and limitations of this concept in respect to neutron flux inhomogeneity, neutron shielding and -ray counting efficiency.     

Determination of trace impurities in electronic grade quartz: Comparison of inductively coupled plasma mass spectroscopy with other analytical techniques

An analytical procedure for the determination of uranium and thorium in the sub-ng/g range as well as of other trace elements in the ng/g to g/g range in high purity quartz samples is described. The results obtained by inductively coupled plasma mass spectroscopy (ICP-MS) are compared to those obtained by other analytical techniques (instrumental neutron activation analysis, INAA; flame atomic absorption spectrometry, AAS; Zeeman graphite furnace atomic absorption spectrometry, ZGFAAS; total reflection X-ray fluorescence analysis, TRFA; direct current arc optical emission spectrometry, DC-arc OES; and X-ray fluorescence analysis, XRFA). For the ICP-MS measurements, the decomposition of the samples is carried out with HF/HNO₃/H₂SO₄-mixtures. The results obtained by the different methods show reasonable agreement. For uranium and thorium, ICP-MS proves to be the most sensitive method: detection limits of about 50 pg/g can be achieved for both elements.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Use of INAA,PGAA, and RNAA to determine 30 elements for certification of an SRM: Tomato Leaves, 157a

Analyses for certification have been made for the determination of 30 elements in the National Institute of Standards and Technology (NIST) Tomato Leaves renewal reference material, SRM 1573a. Three of the analytical techniques used were instrumental neutron activation analysis (INAA), radiochemical neutron activation analysis (RNAA), and prompt gamma activation analysis (PGAA). These techniques provided data on 19 elements by INAA, 10 elements by PGAA, and 7 elements by RNAA, with some overlap between techniques. For example, INAA was able to obtain overall analytical uncerainties (at the 95% confidence level) averaging ±2.2% for major and minor constituents (Ca, Mg, K), ±3.3% for constituents from 1 to 1000 g/g (Na, Fe, Al, Mn, Ba, Zn, Rb, La, Cr), and ±6.4% for elements between 10 and 1000 ng/g (Co, V, Se, Th, Sc, Sb), using sample dry weights of approximately 150 mg. These analyses represent the most extensive use to date of nuclear analytical techniques in the certification of a trace element SRM at NIST.     

Nuclear techniques applied to air particulate matter studies

The most important fraction of aerosols with respect to human health is the respirable fraction, which has particles less than 10 m in equivalent aerodynamic diameter (EAD), the so called PM 10 fraction. The collection of these respirable particles and the determination of their trace element composition is the focus of an IAEA Co-ordinated Research Programme (CRP). The IAEA Laboratory participated in this Programme and established collection sites for the air particulate samples on the grounds of the Atominstitute of the Austrian Universities in Vienna and the IAEA Laboratories, Seibersdorf, representing an urban residential site and a rural site. The collected samples as well as samples of simulated air filters (used also for blind controls) and control materials were analyzed sequentially and/or in sections by X-ray fluorescence (XRF), proton induced X-ray emission (PIXE), instrumental neutron activation analysis (INAA), and atomic absorption spectrometry (AAS). Results demonstrate the applicability of the PM-10 sampling approach, provided PIXE and/or INAA are used in the determinations. Reliable results can be obtained that will lead in comparable air pollution data for many regions in the world through CRP.     

Determination of aluminium contents in selected food samples by instrumental neutron activation analysis

Food and food products are the main sources of Aluminium entering the human body. In order to know aluminium contents in food and food products, selected 26 samples from local market were analyzed by instrumental neutron activation analysis (INAA) using reactor neutrons and high resolution gamma-ray spectrometry. INAA using 1,779 keV γ-ray of ²⁸Al (2.24 min) was used for aluminium concentrations in the range of 33–529 mg kg^?1. Two NIST standard reference materials (SRMs) and two IAEA reference materials (RMs) were analyzed by INAA for quantification of aluminium as a part of method validation.     

Bestimmung von Zink in Thrombocyten mit INAA und AAS

Zusammenfassung Zur Klärung widersprüchlicher Angaben in der Literatur untersuchten wir die Zinkkonzentration von normalen menschlichen Thrombocyten mit Hilfe der instrumentellen Neutronenaktivierungsanalyse (INAA, n=26) und der Atomabsorptionsspektrophotometrie (AAS, n=5 × 6). Wir fanden folgende Fehlerquellen: Zinkkontamination, fehlerhaftes Thrombocytenfeuchtgewicht, Fehler bei der INAA. In den AAS-Proben (n=5 × 6) untersuchten wir zusätzlich die Konzentrationen von Calcium und Magnesium. Wir stellten fest, daß nach Ausschalten der Fehlerquellen die Normalbereiche (¯x ± 2 s) der Elemente Zink, Calcium und Magnesium viel enger liegen als bisher angenommen. Sie betragen, auf das plasmakorrigierte Thrombocytenfeuchtgewicht bezogen: Zn=26,5–32,3 g/g; Ca= 567–693 g/g; Mg=178–218 g/g.

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Determination of zinc in platelets by INAA and AAS

Summary To clarify discrepancies in the literature we determined the concentration of zinc in normal human platelets using instrumental neutron activation analysis (INAA, n=26) and atomic absorption spectrophotometry (AAS, n=5 × 6). We detected the following sources of error: zinc contamination, erroneous platelet wet weight, errors when using INAA. Additionally, we determined the concentrations of calcium and magnesium in the AAS-samples (n=5 × 6). We observed that after elimination of the sources of error the normal ranges (mean ± 2 SD) for the elements zinc, calcium and magnesium are far closer than hitherto believed. Based on platelet wet weight corrected for plasma, they are: Zn=26.5–32.3 g/g; Ca= 567-693 g/g, Mg =178–218 g/g.

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Herrn Prof. Dr. W. Fresenius zum 70. Geburtstag gewidmet     

The effect of other activities on INAA limits of detection

The instrumental neutron activation analysis (INAA) Advance Prediction Computer Program (APCP) is described, as well as its areas of usefulness. Particular attention is devoted to its ability to predict g and ppm INAA lower limits of detection (LOD's) of any particular elements of interest in any sample matrix type of even very approximately known average or typical elemental composition. In general, INAA g LOD's are found to be 10 to 100 times higher than the corresponding interference-free values, and INAA ppm LOD's are found to be 100 to even 100 000 times higher than the corresponding interference-free values calculated for a one-gram sample.