Epithermal instrumental neutron activation analysis of biological reference materials for iodine

Epithermal instrumental neutron activation analysis (EINAA) methods have been optimized and applied to several biological reference materials and selected food items for the determination of iodine. The method involves irradiation of the samples for different periods in epi-cadmium and/or epi-boron flux of the Dalhousie University SLOWPOKE-2 reactor and direct counting without any pre-treatment on a 25-cm³ hyperpure Ge detector. The 443 keV photopeak of ¹²⁸I is used for assaying the iodine content. Precision of measurements, expressed as the relative standard deviation, is 10–15% at 200–500 ppb and 3–12% at 500–6000 ppb levels of iodine. Accuracy of iodine measurements is within 5%. The detection limits for iodine in several biological materials with cadmium and boron, either alone or a combination of the two, as thermal neutron shields have been found to vary between 0.1 and 0.4 mg · kg^–1 for different periods of irradiation, decay and counting. The results suggest that the EINAA methods can be successfully applied to biological materials for routine analysis of iodine at levels higher than 200 ppb.     

Determination of magnesium in botanical reference materials by instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) was applied to the rapid determination of magnesium in the botanical reference materials Beech Leaves-100 and Spruce Needles-101. The magnesium content was quantitatively determined by measuring the gamma-ray photopeak at 1014 keV of the short-lived radionuclide²⁷Mg (9.46 m). The magnesium concentrations in the two materials were found to be 834.6±50.2 g·g^–1 dry weight and 618.6±36.2 g·g^–1, respectively. When assaying a 0.1 g sample under the same experimental conditions the limit of detection is 30 g of Mg.Work carried out at Risø National Laboratory, Isotopes Division, DK-4000 Roskilde, Denmark.     

Multielement standards for instrumental neutron activation analysis of biological materials

Standards for instrumental neutron activation analysis (INAA) of biological materials are proposed. The standards are multielement solid solutions in phenol-formaldehyde resole resin (PFR) moulded as pellets weighing 30 to 50 mg. The concentrations of trace elements in the standards are selected so that, firstly, they are commensurable with their concentrations in the biological materials and, secondly, that the analytical lines of each of the elements incorporated in PFR are resolved with the aid of modern equipment. The principal standard contains 21 trace elements from among those of greatest interest for INAA of biological materials. This standard is recommended for work on high-resolution equipment. At the same time, standards of simpler trace element composition have been prepared and studied which can be used in work on simpler equipment or in solving particular problems in determination of certain groups of chemical elements.     

Uncertainty assessment in instrumental neutron activation analysis of biological materials

Summary The expression of measurement uncertainties in a standardized form is a requirement for result reliability as it imposes implications to the interpretation of analytical results. In this work, sample mass, elemental standard mass, element decay constant and sample and elemental standard activities were identified as the most important uncertainty sources for the relative method of instrumental neutron activation analysis. The contribution of these sources to the expanded standard uncertainty in the concentration of As, Co, Cr, Fe, K, Na, Se and Zn in biological materials of marine origin was assessed and sample activity was identified as the major contribution.     

Establishment of reference materials for Nigeria using instrumental neutron activation analysis

This work has been motivated by the need to establish reference materials from locally available sources. Neutron Activation Analysis (NAA) with Ge(Li) detector has been used to determine 26 elements in seven homogeneous clay samples with a wide range of composition. Short half-life nuclides (10s-10 m) were used to assay Na, Mg, K, Tl, Al, V, Mn, Ba, Dy, Ca and U by a fast rabbit transfer system. The long-lived nuclides were used to assay Sc, Sm, Cr, Eu, Ce, Cs, La, Fe, Lu, Hf, Co, Rb, Ta, Sb, and Pa(Th) after decay of²⁴Na. The approach was purely instrumental. The accuracy of the resutls was tested by atomic absorption spectrometriy (AAS).     

Multielement comparison of instrumental neutron activation analysis techniques using reference materials

Several instrumental neutron activation analysis techniques (parametric, comparative, and k_o-standardization) are evaluated using three reference materials. Each technique is applied to National Institute of Standards and Technology standard reference materials, SRM 1577a (Bovine Liver) and SRM 2704 (Buffalo River Sediment), and the United States Geological Survey standard BHVO-1 (Hawaiian Basalt Rock). Identical (but not optimum) irradiation, decay, and counting schemes are employed with each technique to provide a basis for comparison and to determine sensitivities in a routine irradiation scheme. Fifty-one elements are used in this comparison; however, several elements are not detected in the reference materials due to rigid analytical conditions (e.g., insufficient length of irradiation or activity for radioisotope of interest decaying below the lower limit of detection before counting interval). Most elements are normally distributed around certified or consensus values with a standard deviation of 10%. For some elements, discrepancies are observed and discussed. The accuracy, precision, and sensitivity of each technique are discussed by comparing the analytical results to consensus values for the Hawaiian Basalt Rock to demonstrate the diversity of multielement applications.     

Determination of silver in biological reference materials by neutron activation analysis

Silver in selected, predominantly biological, reference materials (NIST SRM 1515, 1547, 1549, 1566a, 1571, 1577b, 2704, CTA-OTL-1, and Bowen’s Kale) was determined using neutron activation analysis (NAA) in two different analytical modes: instrumental NAA with epithermal neutrons (ENAA), and NAA with radiochemical separation (RNAA). The ENAA mode was based on long-time 5-hour irradiation of samples in a special Cd lined box with counting after 8-month decay. The RNAA procedure consisted in 20-hour irradiation of samples, their decomposition/dissolution by alkaline-oxidative fusion, and precipitation of AgCl including several purification steps. Both methods provided Ag contents in the analyzed reference materials consistent with certified and/or literature values down to the ng·g⁻¹ level.     

Determination of trace elements in biological materials by instrumental epithermal neutron activation analysis

The use of reactor epithermal neutrons in instrumental activation analysis is described for the determination of trace elements via long-lived isotopes. A boron carbide filter is used. Results of analyses of human erythrocytes, plasma, urine and some biological reference materials are given to demonstrate the applicability of the method to biological samples. Bromine, iron, cesium, rubidium, selenium and zinc and cobalt are determined. The method provides accuracy and reliability similar to conventional thermal neutron activation but is faster. Limits of detection attainable with the two techniques are compared.     

Low uncertainty determination of manganese and vanadium in environmental and biological reference materials by instrumental neutron activation analysis

The elements Mn and V were determined by INAA in about 5 mg and 100 mg aliquots of NIST SRM 1648 to elucidate discrepancies between our previous results for the 0.5 mg to 15 mg aliquots and the NIST certified and/or information values. Simultaneously, other NIST SRMs 1633a, 2704, and BCR CRMs 038, 101 and 143 were also analyzed. Special attention was given to evaluating and minimizing uncertainties of all steps of analysis. Our results compared very well with the respective certified and/or information values (if available) of all SRMs and CRMs studied, except for NIST SRM 1648. For this SRM we have found significantly lower results than the NIST values which suggests that the NIST values are positively biased by about 10%. A new value for V in BCR CRM 143 was also obtained.     

Rapid measurement of selenium in biological samples using instrumental neutron activation analysis

A rapid instrumental system for measuring selenium via 17 second^77mSe has been applied to the analysis of a wide variety of biological specimens encountered in biomedical research. The reliability and versatility of the method is documented for serum and animal tissue specimens. Analysis results for SRM 1577 bovine liver show excellent accuracy and precision.     

Determination of 34 elements in Chinese geochemical standard reference materials by instrumental neutron activation analysis

Thirty four elements (Al, As, Ba, Br, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Gd, Hf, Ho, K, La, Lu, Mg, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, Ti, U, V, W, Yb) were determined by instrumental neutron activation analysis in the second set of Chinese geochemical standard reference materials (sediments from GSD-9 to GSD-12, soils from GSS-1 to GSS-8, rocks from GSR-1 to GSR-6) using both thermal and epithermal irradiations. Irradiation schemes designed to utilise short, medium and long-lived nuclides were employed in order to analyse major, minor and trace elements with different half-lives. The gamma-ray spectra were measured by Ge(Li) and HP(Ge) detectors. Relevant nuclear data and possible interferences are listed, and analytical results are presented and discussed.     

Determination of multielement in optical waveguide and standard reference materials by instrumental neutron activation analysis

Trace amounts of transition elements (Co, Cr, Cu, Fe, Mn and V) and other seven elements in optical waveguide samples were determined by INAA. The contents of impurities in ultra-pure materials are less than those of high-purity materials and of G.R. grade. The increase of contamination of trace transition elements and iridium from furnace or crucible are observed in the production of optical glass fibers. Up to seventeen elements were determined in five NBS biological standard reference materials: Oyster Tissue: SRM-1566, Brewers Yeast: SRM-1569, Spinach: SRM-1570, Orchard Leaves: SRM-1571 and Tuna Fish, and in four Japanese biological standard reference materials: Tea Leaves B&C, Pepperbush and Shark Meat. The analytical results in NBS and Japanese standard reference materials are in good agreement with published values and certified values by NBS.     

Geological reference materials for standardization and quality assurance of instrumental neutron activation analysis

Results are presented from the INAA of 34 elements in NIST and USGS geological reference materials that were analysed relative to multielemental SRM-1633a Coal Flyash standards. The data compare favorably with works reported by other investigators. The application of historical control charts for continuous monitoring of quality assurance and detection of systematic errors is demonstrated.     

Determination of 25 elements in biological standard reference materials by neutron activation analysis

Trace element analysis has been carried out on standard biological reference samples such as bovine liver, orchard and tomato leaves. Computer aided instrumental neutron activation analysis and, in some cases, preliminary chemical group separation followed by NAA were used. For Ca, Mg, Ni and Si special chemical separation and Cerenkov counting were applied. *** DIRECT SUPPORT *** A1353068 00003     

Low level determination of manganese in biological reference materials by neutron activation analysis

A simple method was developed for the low level determination of manganese in biological materials by neutron activation analysis with radiochemical separation based on manganese dioxide precipitation. Precision and accuracy of the method were tested by analyses of IAEA reference materials Animal Muscle H-4, Milk Powder A-11, Freeze Dried Animal Blood A-13, Horse Kidney H-8, and Mixed Human Diet H-9. Interferences from iron and cobalt were also evaluated.     

Advantages of boron filters in instrumental epithermal neutron activation analysis of biological materials

Boron carbide (B₄C) and boron nitride (BN) irradiation filters have been constructed and used for epithermal neutron activation analysis of biological materials. The major advantage offered by these filters in this application is the substantial reduction of interfering matrix activities. Consequently some trace elements of interest can be determined instrumentally with minimum delay. The filters are particulary beneficial if utilized in short reactor irradiations for rapid analysis of biological materials.     

Vanadium determination in rat tissues and biological reference materials by neutron activation analysis

Vanadium was determined in adrenal gland, brain, ileum, kidney, liver, lung, muscle, myocard, skin, spleen, gonads, thyroid, and tibia of rats fed with normal diet and exposed to high vanadium doses in drinking water. Both radiochemical neutron activation analysis (RNAA) and instrumental neutron activation analysis (INAA) were employed. The RNAA procedure consisted in dry ashing samples prior to irradiation and vanadium separation from the irradiated samples by extraction with N-benzoyl-N-phenylhydroxylamine (BPHA) in toluene from 5 mol·l^–1 HCl. Vanadium accumulation as a function of a type of the tissue, exposure time, sex of rats, and administration of V(IV) or V(V) was studied. For quality assurance purposes, the biological (standard) reference materials NBS SRM 1571 Orchard Leaves, NBS SRM 1577a Bovine Liver, IAEA H-4 Animal muscle, and Bowen's Kale were analyzed.Presented at the 2nd Balkan Conference on Activation Analysis and Nuclear-Related Analytical Techniques, Bled, 4–6 October, 1989.