Instrumental Neutron Activation Analysis Procedures Research Articles

The efficacy of neutron activation analysis for homogeneity testing of CRMs candidates of soil matrices

ABSTRACT Certified reference materials (CRMs) are the cornerstone of the quality of analytical measurements. Homogeneity is a critical process in CRMs development. This study reports the use of instrumental neutron activation analysis (INAA) for the assessment of between-bottle homogeneity of four CRMs candidates of soil matrices, namely, soil from an agricultural area, soil from an industrial area, urban street dust, and surface marine sediment. The study also reports informative findings on the precision of INAA, besides uncertainty and detection limits (DLs). Eleven elements including nine toxic heavy metals (Cr, Fe, Mn, Co, Ni, Cu, Zn, As, and Cd) and two reference elements (Al and Si) were examined. Reference elements are used for the assessment of source contribution, i.e. crustal and anthropogenic, of elements. The uncertainty values of Al, Cr, Fe, Mn, Co, and As were < 5%, suggesting excellent accuracy of the INAA procedure, while the uncertainty ranges of Si and Zn contents were 10–40% and 1–16%, suggesting less accuracy than other examined elements. The uncertainty of Cd and Ni contents was not reported as they were below the DLs. Co recorded the lowest DL (0.15–0.27 µg/g) followed by As (0.27–0.56 µg/g), Mn (0.68–1.26 µg/g), and Cr (0.88–1.67 µg/g). The homogeneity was assessed based on the relative standard deviation (RSD) of seven bottles out of seventy bottles produced for a feasibility study purpose. For the CRM candidate of soil from an agricultural area, five elements (Cr, Mn, Fe, Co, and Zn), out of eight elements, recorded RSD less than 5%, indicating good homogeneity. For the CRM candidate of soil from an industrial area, seven elements recorded RSD% less than 2%, indicating excellent homogeneity. For the dust CRM candidate, six elements recorded RSD < 2%, indicating excellent homogeneity as well. Good homogeneity of the sediment CRM candidate was also obtained since six elements recorded RSD < 5%.

Tellurium determination by three modes of instrumental neutron activation analysis in aerosol filters and trap solutions for the simulation of a severe nuclear accident

Tellurium belongs to the elements not frequently determined by neutron activation analysis (NAA) or other analytical methods. We present results of a new methodological study using three independent modes of instrumental NAA (INAA) using the 123mTe, 131Te and 131I radionuclides. We compare the results obtained in terms of accuracy, precision and limits of detection (LOD). We utilized the INAA procedures tested for the tellurium determination in aerosol filters and trap solutions in a model experiment aimed at reducing the knowledge gap concerning the behaviour of 132Te, a radiologically significant fission product, which constitutes a considerable health risk towards the public in case of its release in a severe nuclear power plant accident. We found that the nuclear reaction 130Te(n,γ)131Te and gamma-ray spectrometric measurement of 131I, a descendant of 131Te, is the most sensitive way of Te determination by INAA providing as low LOD values as 0.15 µg of Te in the Teflon aerosol filters and 0.22 µg mL-1 in the 0.1 M NaOH trap solutions. The three independent INAA modes allowed employing the self-verification principle of INAA for increasing the trustworthiness of our results. Finally, we also point to the indispensable role of the non-destructive feature of INAA for assay of samples, such as Teflon aerosol filters, that are difficult to be analysed by other analytical methods requiring complete sample destruction without analyte losses.

Experimental design and z-score results are useful tools for optimizing instrumental neutron activation analysis procedures

In this study 2k experimental designs were used for the optimization of an instrumental neutron activation analysis method for the determination of bromine, chlorine, magnesium, manganese, potassium, sodium and vanadium in biological matrix materials. Depending on radionuclide half-lives, 23 or 24 experimental designs were used with irradiation time, sample–detector distance, counting time and sample decay time as factors. Gamma ray spectrometer, comparator mass fraction and sample mass were kept constant. Optimized irradiation and measurement conditions were established based on the experimental design results that used z-scores as response on a reference material for the various elements and experimental conditions.

Application of neutron activation analysis to micro gram scale of solid samples

An instrumental neutron activation analysis (INAA) procedure for analyzing extremely small samples was developed and applied to two kinds of extraterrestrial samples. A few mg of the Allende meteorite as well as the JB-1 basalt can work well as a reference sample for a relative method. To evaluate the applicability of this INAA procedure, detection limits are presented and compared with the elemental contents in a potential sample to be analyzed. The possibility of reuse of neutron-irradiated samples for mass spectrometry was noted by indicating degree of increase in isotopic abundance for noble gas and long-lived radioactive nuclides.

Challenges and successes in the use of neutron activation analysis procedures for value assignment of animal serum and bovine liver Standard Reference Materials

Analyses for value assignment in the renewal Standard Reference Materials® SRM 1598a Animal Serum and SRM 1577c Bovine Liver included extensive characterization by neutron activation analysis (NAA). Conventional instrumental NAA procedures were complemented by pre-irradiation chemical separations for the determination of Al, V, Mn, and Cu, radiochemical separations for the determination of Ag, As, Cd, Cr, Cu, Mo, Sb, and Se, and the use of (anti-) coincidence gamma-ray spectrometry systems for the instrumental determination of Ag, Cr, and Hg. The previous materials, SRMs 1598, 1577, and 1577b, were analyzed together with the new materials for quality control.

Arsenic speciation: HPLC followed by ICP-MS or INAA

Sensitivities for the measurement of four arsenic species, AsIII, AsV, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), in environmental waters and rice extracts by a new neutron activation analysis (NAA) method using pre-separation of the species by liquid chromatography were determined. A manual fraction collection was used to isolate the species, followed by instrumental neutron activation analysis procedures. The sensitivities determined for arsenic species in the samples varied from 1.21 to 1.47 ng per vial or about 30 μg·L−1 in sample solutions which translates to about 900 ng arsenic per gram of rice for our HPLC-NAA experiments.

Characterization of Brazilian commercial milks by instrumental neutron activation analysis

Aiming at the determination of toxic and essential elements in Brazilian commercial bovine milk, 25 ultra high temperature (UHT) milk samples were acquired in the local market of Piracicaba, SP. The samples were freeze-dried and analyzed by instrumental neutron activation analysis (INAA) allowing the determination of Br, Ca, Co, Cs, Fe, K, Na, Rb and Zn. When the results were expressed as concentration (mg·l−1) no significant differences were found. However, considering the dry matter, results showed a clear difference between the mass fractions (mg·kg−1 d.w.) of skim milk and whole milk for the elements Br, Ca, K, Na, Rb and Zn, indicating that the removal of fat caused a concentration effect in the dry matter of skim milks. Discrepancies were found between the concentrations of Ca and Na measured by INAA and the values informed in the labels. Ca showed variations within 30% for most samples, while concentrations of Na were up to 190% higher than informed values. The sample preparation and the INAA procedure were appropriate for the determination of Br, Ca, Co, Cs, Fe, K, Na, Rb and Zn in milk samples.

Investigations by INAA for the Development of Natural Matrix Standard Reference Materials® (SRMs) Suitable for Small Sample Analysis

Instrumental neutron activation analysis (INAA) procedures were optimized for the analysis of small (1 mg) solid samples. This process included sample handling as well as detailed evaluation of high rate counting techniques, also in conjunction with rapidly decaying sources, to establish the necessary analysis environment for the determination of large numbers of samples with high reproducibility. The investigated materials included biological materials such as peach leaves (SRM 1547), lichen, and bovine liver, as well as environmental materials such as urban particulate matter (SRM 1648), and deep ocean sediment. The analytical data obtained with the INAA procedures were used to determine homogeneity values.

Determinations of subnanomole elemental levels by NAA and their possible impact on human health related issues.

Neutron activation analysis (NAA) is an appropriate tool for the determination of trace elements in biological systems. The virtually blank-free NAA procedures fittingly complement precautions employed in sampling and sample preparation of biological matrices. Results from instrumental NAA procedures used to establish baseline values and time trends for elements in human tissues demonstrate the advantages as well as the limits of these procedures for nanomole and, in a considerable number of instances, subnanomole elemental levels. In addition, subnanomole mass fractions have been determined with extremely low limits of detection by employing NAA with radiochemical separations isolating very low levels of radioactivity from the matrix background. The elements reviewed in this article include Cr, Se, Pt, and others that have been determined by NAA at subnanomole levels in human tissues and body fluids and in biological macromolecules.

Quantitative Filter Debris Analysis (QFDA) as a means of monitoring wear in oil-lubricated systems

In this study, the trace analytical technique of instrumental neutron activation analysis (INAA), using the SLOWPOKE-2 Facility at RMC, was used to develop an application termed Quantitative Filter Debris Analysis (QFDA). The preliminary step, which consisted of the quantitative analysis of filter debris samples from CH-124 Sea King helicopter main gear boxes (MGB) for 19 elements associated with engine wear, confirmed that distinct ranges of normal and abnormal wear rates exist in the CH-124 MGB and, more importantly, validated the INAA procedures. The second step, which consisted of the analysis of both oil and filter debris samples from the CF-188 Hornet aircraft engine by the INAA technique and an Atomic Emission (AE) method, confirmed that little useful wear information can be found in the oil of a finely-filtered engine system and demonstrated the potential of QFDA as a means of monitoring wear by analyzing the oil filter debris. What appears to be normal wear rate ranges were identified for the CF-188 Hornet aircraft engine. The potential of monitoring the wear health of oil-lubricated systems using QFDA was confirmed by this investigation.

Simple nitric acid dissolution method for electrothermal atomic absorption spectrometric analysis of atmospheric aerosol samples collected by a berner-type low-pressure impactor

The aim of this study was to develop a simple dissolution method for atmospheric aerosol samples collected using a Berner impactor. Particular care was taken to ensure that the procedural blank contributions were as low as possible for the elements investigated. The impactor samples were treated for two or three 20 min periods with 0.2 mol l–1 nitric acid in polystyrene test-tubes in an ultrasonic bath at 50 °C. Electrothermal atomic absorption spectrometry (ETAAS) with a graphite furnace was used to determine 14 elements: Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V and Zn. With the exception of Zn, for which a platform was used, all analytes were atomized off the wall of the graphite tube. The blank values for Al, Cd, Cu, Mn, Ni, Pb and V were found to be at or below the detection limits of the method. The blank values for Ca, Fe, K, Mg, Na and Zn varied between 0.5 and 3 µg l–1 but Cr showed an unsuitably high blank of 8 µg l–1. The dissolution method was tested on the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1648 Urban Particulate and the recoveries were found to be 80–93% for Pb, Zn, Cd and Cu. The least recoverable elements in this matrix were Al, Cr, Fe, K and Na, with recoveries between 20 and 44%. A prolonged dissolution time had only a minor effect on the recoveries. Additional tests involved the analysis of ambient aerosol samples, collected with a cascade impactor, by both ETAAS and instrumental neutron activation analysis (INAA), with the latter technique providing the reference values. Six elements (Al, Cu, Mg, Mn, Na and V) were measured by both techniques. Compared with the NIST material, the fine particle (equivalent aerodynamic cut-off diameter<2 µm) impactor samples clearly showed better recoveries for Cu (91%), Mn (90%), Na (102%) and V (96%). Similar or even better recoveries are also expected for fine particle Cd, Zn and Pb, which were not measured in our INAA procedure but exhibited the highest recoveries for the NIST material. For Al, on the other hand, the results from the impactor samples were similar to those for the NIST material and there was a trend that the recoveries were decreasing with increasing particle size, because of incomplete dissolution of the soil dust particles and a lower ability of the coarser particles to form a suspension. Moreover, coarse particle Al was recovered mostly as particulate material. It is assumed that our dissolution method is valid for measuring fine particle Cd, Cu, Mg, Mn, Na, Pb, V and Zn in ambient aerosol samples collected on polycarbonate film by various types of impactors.

Non-destructive bone aluminum assay by neutron activation analysis

A non-destructive method based on instrumental neutron activation analysis (INAA) for the assay of aluminum in bone samples is described. The28Al signal obtained upon neutron irradiation includes contributions from both the reaction27Al(n,γ)28Al and31P(n,α)28Al. The first reaction is with the thermal neutrons and the second one is with the fast neutrons. The contribution from the31P reaction is calculated from the fact that Ca/P ratio in bone mineral is constant and the amount of calcium can be measured from the thermal reaction48Ca(n, γ)49Ca. The aluminum values obtained by the INAA procedure agreed within 10% of those obtained by atomic absorption spectrophotometry. With this assay the levels of aluminum in normal bones (<70 μg g−1 apatite) cannot be determined reliably but higher aluminum levles in bone biopsies associated with Al toxicity, e.g. some patients with renal osteodystrophy, can be determined with a precision of ±10%.

Determination of some noble metals in iron meteorites by instrumental neutron activation analysis with a SLOWPOKE reactor

An instrumental neutron activation analysis procedure has been developed which permits the direct determination of Au, Ir, Os and Rh in iron meteorites using a SLOWPOKE reactor. A simple correction method enables the instrumental determination of rhodium using its short-lived nuclide.

Radiochemical and instrumental neutron activation analysis procedures for the determination of low level trace elements in human livers

A comprehensive approach to the analysis of human livers was developed in a pilot program for the National Environmental Specimen Bank that employed a combination of four analytical techniques. Refinements in this approach were needed for improvement in detection limits, more effective sample usage and to reduce the number of analytical steps that were involved. Since neutron activation analysis (NAA) had determined most of the elements, expansion of NAA was chosen to achieve these goals. Modifications in the instrumental NAA procedures, including the use of a Compton Suppressor System, gave increased sensitivity for some low level elements, such as arsenic and chromium. Radiochemical procedures that followed the instrumental counts increased the sensitivity for the elements chromium, selenium, arsenic, molybdenum, silver, antimony, and tin. Results are given for two radiochemical procedures that were applied following the modified procedure, either the use of an inorganic ion exchange column or a liquid/liquid extraction, and these are compared to instrumental results.

Application of an instrumental neutron activation analysis procedure to analysis of food

The capabilities of a relatively simple instrumental neutron activation analysis procedure were demonstrated by performing multielement analyses of 240 Food and Drug Administration Total Diet Studies food composites. The analytical results provide a comprehensive database for a wide range of food types. The procedure incorporates only two irradiations and counts, polyethylene packaging and no sample transfer after irradiation. Concentrations were determined for 19 elements, 16 of which were found in most composites. Detection limits were calculated for all food groups and are given for the 22 elements included in the quantitative analysis scheme. In a qualitative search for 18 additional elements for which no standards were run, none were detected in any of the composites. Specific factors such as interferences from the blank are discussed in regard to their effects on the uncertainties associated with the experimental data and the detection limits. Modifications to the procedure are also suggested for lowering the detection limits for specific elements.

Instrumental neutron activation analysis of brain aluminum in Alzheimer disease and aging.

Instrumental neutron activation analysis procedures were used to determine the aluminum content of various brain regions in histologically verified Alzheimer disease (AD) and in controls. The grand mean aluminum level for 74 AD specimens was 0.372 +/- 0.058 microgram/gm and for 137 adult controls, 0.467 +/- 0.033 microgram/gm, both on a wet weight basis. No difference was found at the bulk sample level between AD and adult controls, corrected for age and sex, or when frontal, temporal, and hippocampal specimens were compared. Control specimens (infancy to 85 years) showed an increase in brain aluminum concentration with age. Comparison of freeze-dried to wet weight ratios of AD and controls revealed a small increase in water content in AD brains.