Determination of iodine in human nails via epithermal neutron activation analysis

An epithermal instrumental neutron activation analysis (EINAA) method, using a boron nitride irradiation capsule compatible with use in the University of Missouri Research Reactor pneumatic-tube irradiation facility, has been developed for the analysis of iodine in human nails. The principal objective was to determine if the nail could be used as a means of monitoring dietary intake of iodine. The EINAA method was used to analyze nails from subjects having iodine intakes that could be qualitatively differentiated. Iodine concentrations in nails from these subjects were positively correlated with apparent iodine intake.     

Uranium in coral skeletons determined by epithermal neutron activation analysis

A simple and non-destructive method has been proposed for the routine determination of uranium by epithermal neutron activation analysis in coral skeletons. Using a cadmium capsule, about 0.1-0.2 g samples were irradiated for 6 hours in the Triga Mark II Reactor. Measurements of -ray (²³⁹Np via ²³⁹U) were performed with each sample and standard after cooling for about three days. Compared with a non-destructive thermal NAA, the present method was found to improve the sensitivity because it reduced the intense Compton background induced by ²⁴Na. We determined uranium in coral standards within 2% of analytical precision. The data obtained for the carbonate standards are mostly consistent with reported values. The present method could be usefully applied to determine uranium contents in fossil corals from the Funafuti Atoll in the Pacific. The distribution of uranium between seawater and coral skeletons is also discussed in order to understand the environmental media in which the coral grew.     

Analysis of foods for iodine by epithermal neutron activation analysis

Epithermal-neutron activation analysis (ENAA) was applied to the analysis of foods for iodine. The procedure involves irradiation of wet foods in a boron nitride, vessel, followed by direct counting of the 442.9 keV gamma ray of¹²⁸I without any processing of the sample. Three research reactors were evaluated for use in determining iodine by ENAA. The University of Virginia reactor at Charlottesville was chosen for this study because the reactor facilities minimized thermal heating of the boron nitride vessel, enabling irradiation of larger, more representative analytical portions. Iodine concentrations ranging from <0.003 to 0.74 g/g are reported for 17 different food matrices.     

Estimates of iodine in biological materials by epithermal neutron activation analysis

Iodine abundances in NBS biological SRMs and various organs of rats were evaluated by epithermal neutron activation analysis with a boron carbide filter. Detectability of iodine in different biological materials by this method is discussed.

     

Determination of iodine in human brain by epithermal and radiochemical neutron activation analysis

Despite the role of iodine for proper development of the brain and the functions of the element, the accurate data on its concentration in brain tissue are largely lacking, the main reason being analytical difficulties associated with determination of the element especially at low levels. In this work, samples from human brain regions from Hungarian patients were analyzed using epithermal and radiochemical neutron activation analysis (ENAA and RNAA, respectively). The RNAA procedure is based on alkaline-oxidative fusion followed by extraction of elemental iodine in chloroform. The results were checked by the analysis of biological standard reference materials, namely bovine liver, bone meal and diet, and by comparison with previous results obtained by a different RNAA procedure.     

Determination of iodine in Asian diets by epithermal and radiochemical neutron activation analysis

Samples of diets from China, Japan, Korea, India, Pakistan and Philippines were analyzed using epithermal and radiochemical neutron activation analysis (ENAA and RNAA, respectively) within the framework of the IAEA project “Reference Asian Man”. The RNAA procedure was based on alkaline-oxidative fusion followed by extraction of elemental iodine in chloroform. The analytical methods employed are discussed in terms of detection limits and uncertainties of the results obtained. For quality control purposes a number of NIST biological reference materials, namely diets and foods were analyzed. Results for the diet samples indicate that achieving the WHO recommended daily allowance for iodine may be a problem in most of the above given countries. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparative determination of bromine and iodine in three air sampling media via instrumental thermal and epithermal neutron activation analysis

A comparative determination of bromine and iodine in three distinct air sampling media by instrumental thermal and epithermal neturon activation analysis is presented. Open ocean air samples from the mid-Atlantic region were collected on ultra-pure nylon, Nuclepore, and activated charcoal substrates. The bromine and iodine content of each substrate was determined by both epithermal and thermal activation techniques. Good agreement was found within most thermal-epithermal pairs. Relative to the thermal activation procedure, the epithermal technique yields peak/background ratio improvements ranging from a factor of 1.30 to 9.5. Nylon substrates showed the smallest improvement at 1.30 and both Nuclepore and activated charcoal substrates showed improvement factors of 6.7 and 9.5 for bromine and iodine respectively.     

Determination of bromine and iodine in biological and environmental materials using epithermal neutron activation analysis

Epithermal neutron activation analysis (ENAA) was applied to the determination of the contents of bromine and iodine in 40 biological and environmental standard reference materials and Chinese diets. Boron nitride (BN) for solid samples and BN+Cd for liquid samples were adopted as shield material. Irradiation was carried out in inner and outer irradiation sites in a Miniature Source Reactor (MNSR) for solid and liquid samples, respectively. The 443 keV photopeak of ¹²⁸I and the 616 keV photopeak of ⁸⁰Br were used. The precision of measurement (relative standard deviation) is 2∼6% for contents of iodine of more than 100 ng/g and 8∼12% in the 20∼100 ng/g range in solid samples, and 12∼18% at less than 100 ng/ml in liquid samples. For bromine, the precision of measurement is 2–8% for solid samples and lower than 13% for liquid samples. The detection limits under experimental conditions varied between 10∼30 ng/g, 55∼95 ng/g and 25∼68 ng/g for iodine and 50∼150 ng/g, 200∼450 ng/g and 100∼300 ng/g for bromine in ENAA with BN shield in inner irradiation sites, with Cd shield and BN+Cd shield in outer irradiation sites, respectively. Received: 13 June 1996 / Revised: 2 September 1996 / Accepted: 19 September 1996     

Determination of iodine in milk products and biological standard reference materials by epithermal neutron activation analysis

The biologically essential trace element, iodine, has been determined in various milk products by epithermal neutron activation analysis /ENAA/ after sealing in quartz and irradiating under cadmium cover. The method was extended to several IAEA and NBS biological reference materials.     

The epithermal neutron flux distribution in a nuclear reactor and its effect on epithermal neutron activation analysis

The shape of the epithermal neutron energy distribution has been determined in two irradiation positions of the University of London CONSORT II reactor. The method applied involves cadmium ratio measurements using a series of resonance detectors. Principles of the method and some considerations relative to epithermal neutron activation analysis in connection with the deviation of the epithermal neutron flux distribution from the 1/E law are given.     

Trace multielement analysis in boron materials by epithermal neutron activation analysis

A method, based on epithermal neutron activation analysis using a boron filter is described for the determination of ～60 trace elements in boron and its compounds. The method has an accuracy of ～20%, a precision of ～15% RSD and limits of detection for most elements are either at the sub-ppm or low ppm levels. The method requires no sample preparation and is economical in effort.     

Determination of bromine, chlorine and iodine in environmental aqueous samples by epithermal neutron activation analysis and Compton suppression

Summary Halides, particularly Br^- and Cl^-, have been used as indicators of potential sources of Na⁺ and Cl^- in surface water and groundwater with limited success. Contamination of groundwater and surface water by Na⁺ and Cl^- is a common occurrence in growing urban areas and adversely affects municipal and private water supplies in Illinois and other states, as well as vegetation in environmentally sensitive areas. Neutron activation analysis (NAA) can be effectively used to determine these halogens, but often the elevated concentrations of sodium and chlorine in water samples can give rise to very high detection limits for bromine and iodine due to elevated backgrounds from the activation process. We present a detailed analytical scheme to determine Cl, Br and I in aqueous samples with widely varying Na and Cl concentrations using epithermal NAA in conjunction with Compton suppression.     

Measurement of bromide ion used as a solute-transport monitor via epithermal neutron activation analysis

In soil science (ca. 1970), bromide ion (Br⁻) in various forms (e.g., KBr, NaBr, SrBr₂) was introduced as a non-reactive stable tracer in solute transport studies normally moving freely with the flux of water without substantial chemical or physical interactions with the soil. Typically, Br⁻ is extracted from soil and quantified using either a bromide selective electrode (sensitivity is ≈10μg/ml) or by high-performance liquid chromatography (sensitivity is ≈0.010 μg/ml). Where the sensitivity is adequate, the selective conductivity method, which is simple, affordable and fast, is preferred. More recently (ca. 1990), workers have reported that 20% of Br⁻ tracers, at low groundwater pH, may be adsorbed by iron oxides and kaolinite when present in the alluvial aquifer. We investigated the use of Epithermal Neutron Activation Analysis (ENAA) as a means of measuring Br⁻ directly in soil samples without an extraction. ENAA was chosen because of its high theoretical advantage factor over aluminum (i.e. ≈20), the principal interfering soil constituent, calculated for the⁷⁹Br(n,γ)⁸⁰Br reaction compared to²⁷Al(n, γ)²⁸Al. Br⁻ was measured (sensitivity is ≈0.050 μg/g) in one gram soil samples from a 5 s irradiation (φ_epi=2.5·10¹² n·cm^-2·s^-1) using a BN capsule.     

Determination of silver using cyclic epithermal neutron activation analysis

A fast pneumatic transfer facility was installed in Nuclear Engineering Teaching Laboratory (NETL) of the University of Texas at Austin for the purpose of cyclic thermal and epithermal neutron activation analysis. In this study efforts were focused on the evaluation of cyclic epithermal neutron activation analysis (CENAA). Various NIST and CANMET certified materials were analyzed by the system. Experiment results showed ¹¹⁰Ag with its 25 s half-life as one of the isotopes favored by the system. Thus, the system was put into practical application in identifying silver in metallic ores. Comparison of sliver concentrations as determined by CENAA in CANMET certified reference materials gave very good results.     

Detection limits in epithermal neutron activation analysis of geological material

The improvement of detection limits for trace elements in geological samples by epithermal neutron activation analysis is examined. The relative merits of cadmium, boron and composite cadmium+boron filters are compared for trace elements Ni, As, Pd, Cd, Sb, W, Ir, Pt and Au, and interfering elements Na, K, Sc, Cr, Fe, Co and Cu. A boron filter gives optimum sensitivity for the trace elements based on interference from⁴⁶Sc, but the detection limits are only improved 2–5 times. Ma imum possible improvement, which is shown by Ni, gives sensitivities 5 times better under cadmium and 15 times under boron.     

A technique for reducing interferences in epithermal neutron activation analysis

A new epithermal neutron activation technique is described. The technetium is based on the existence of non-overlapping resonance peaks in the neutron absorption cross-section spectra for the nuclides present in the sample to be analyzed. By this method it is possible to reduce some of the interfering activities with respect to the sought activity by using appropriàte filters. An experiment has been carried out to demonstrate the validity of the technique.     

Thermal and epithermal neutron activation analysis using the monostandard method

A new approach is presented for neutron activation analysis using the monostandard (single comparator) method. Elements to be determined are classified into two groups; those with σ_o>I_o are activated with whole neutron spectrum (without Cd-cover), using a standard of the same group (e.g. Sc), while elements with I_o>σ_o are activated with epithermal neutrons (under Cd-cover) using a standard of the same group (e.g. Au or Co). Epithermal activation increases the number of determinable elements and its coupling with the monostandard method has the advantage of using a small Cd-cover. The σ_o and I₀ values of some elements were determined to test this approach.     

Determination of uranium in salt solutions containing high levels of lanthanides via epithermal neutron activation analysis

Epithermal Instrumental Neutron Activation Analysis has been used to measure the concentration of uranium in eutectic salt solutions in support of a research program in which the actinide elements are separated from rare earths and other fission products using high-temperature electo-deposition. The uranium response over three decades in concentration follows a negative power function; and high concentrations of samarium interfere with the determination of uranium but can be accurately corrected. The EINAA method was successfully used to analyze NIST SRM 278 Obsidian and NIST SRM 1566a Fly Ash.     

Investigations on the comparator technique used in epithermal neutron activation analysis

The possible extension of the comparator technique of reactor neutron activation analysis into the field of epithermal neutron activation has been investigated. Ruthenium was used for multi-isotopic comparator. Experiments show that conversion of the so-called reference k-factors—determined by irradiation with reactor neutrons—into k_epi-factors usable at activation under cadmium filter, can be evaluated with fair accuracy. Sources and extent of errors and their contribution to the final error of analysis are discussed. Based on the paper presented at the 2nd European Conference on Analytical Chemistry, 25–30 August, 1975, Budapest, Hungary.     

Silicon determination in plant materials by instrumental epithermal neutron activation analysis

The Si determination with epithermal neutrons using the reaction²⁸Si (n,p)²⁸Al is described. Thermal neutrons are eliminated from the irradiation position with a BN-shield. Two first order interfering reactions with P and with Al necessitate appropriate corrections. The interfering reaction on Al is shown to depend heavily on the hydrogen (H) content of the sample, which therefore must be taken into account. The lower application range in plant samles is estimated to be 500 g g^–1. Reproducibility is <5% in suitable cases, but not as good if the necessary corrections are large. The capacity is 25 samples per 8 h. The method is applied to 3 plant standards (rice, hay and pine needles) and to 47 samples of spruce needles. The applicability to different plant materials is mainly limited by their relative Al, P and Si concentrations. Literature values are use to find plant categories in which Si can be reasonably determined by instrumental epithermal neutron activation analysis (IENA).