Determination of trace cadmium and other elements in bone by epithermal neutron activation analysis

Epithermal neutron activation analysis (ENAA) was applied to measure quantitatively Cd and other elements in bone samples from control and Cd-fed rats. This method was found to be non-destructive to the bone samples, with no sign of radiolytic charring and was sensitive enough to detect and quantify Cd in bone samples at normal levels for mammals (viz. 0.5–1.0 g/g) and higher. Two different thermal neutron shield materials were utilized, namely cadmium and boron. The boron shield resulted in a 27% improvement in the detection limit of Cd in bone. The accuracy of ENAA for Cd was assessed by intercomparison with electrothermal atomic absorption spectrophotometry (ETAAS), and the results were in fair agreement (±23%) with those from ENAA.     

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 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.     

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.     

Determination of palladium by adsorptive stripping voltammetry

 Adsorptive accumulation of the Pd(II) complex with dimethylglyoxime was evaluated for stripping voltammetry with respect to different parameters. The sensitivity of the method and the linearity between the peak current and the concentration of Pd(II) depends on the ionic strength, the electrode area, the preconcentration time, the transport rate to the electrode, and the potential scan rate. The most appropriate medium was 0.1 mol/L acetate buffer between pH 3.5 and 4. Using 2 min of preconcentration at a 2.6 mm² electrode and the differential pulse mode, a detection limit of 0.05 μg/L Pd was achieved for liquid samples and 50 ng/g for solid samples. Different aqueous and solid samples were analysed and the recovery from biological and inorganic materials investigated. Received: 29 February 1996/Revised: 29 July 1996/Accepted: 1 August 1996     

Determination of the total amount of organically bound chlorine,bromine and iodine in environmental samples by instrumental neutron activation analysis

The determination of chlorine, bromine and iodine present as non-polar, hydrophobic hydrocarbons in environmental samples is reported. The organohalogen compounds are separated from water into an organic phase by on-site liquid—liquid extraction, and from biological material by procedures based on lipid phase extraction and codistillation. After removal of inorganic halides by washing with water and concentration of the sample by evaporation of the solvent, the resulting extracts are analyzed for their chlorine, bromine and iodine contents by instrumental neutron activation analysis. Strict attention is paid to the possibility of contamination in every step of the procedure. Background values in routine analysis are approximately 100–200 ng of chlorine, <5 ng of bromine and <3 ng of iodine.     

The determination of bromine in dry biological material by instrumental neutron activation analysis

Procedures for the determination of bromine by the reactions⁸¹Br(n, γ)⁸²Br (T=35.4 h) and⁷⁹Br(n, γ)^80mBr (T=4.4 h). In the case of⁸²Br a flat coaxial Ge(Li) crystal is used to measure the 619 keV photopeak. For^80mBr a planar Ge(Li) detector is applied to measure the 39 keV γ-ray. The agreement between the data obtained with both techniques for some Standard Reference Materials is satisfactory.     

Availability of essential trace elements in medicinal herbs used for diabetes mellitus and their possible correlations

Four plant parts (leaves, roots, fruits and seeds) of twenty samples of sixteen antidiabetic herbs including three commercially marketed capsules have been analyzed for 6 minor (Na, K, Ca, Cl, Mg, and P) and 21 trace (As, Ba, Br, Ce, Co, Cr, Cs, Cu, Eu, Fe, Hg, La, Mn, Rb, Sb, Sc, Se, Sm, Th, V and Zn) elements by instrumental neutron activation analysis (INAA). Further, Ni, Cd and Pb contents were determined by AAS. Elemental data were validated by simultaneously analyzing reference material (RM), MPH-2 Mixed Polish Herbs. Several elements such as Cr and V (1–2 μg/g), Rb (10–40 μg/g), Cs (80–300 ng/g), Se (∼100 ng/g) and Zn (25–60 μg/g) play an important role in diabetes mellitus. Interelemental linear correlations have been observed for Cu vs. Zn (r = 0.89) and Rb vs. Cs (r = 0.87). K/P ratio varies in a narrow range with a mean value of 6.2 ± 1.4. Toxic elements As and Hg were found in <1 μg/g whereas Cd and Pb were in ∼5 μg/g and <10 μg/g, respectively.     

Determination of water-soluble and insoluble (dilute-HCl-extractable) fractions of Cd,Pb and Cu in Antarctic aerosol by square wave anodic stripping voltammetry: distribution and summer seasonal evolution at Terra Nova Bay (Victoria Land)

Eight PM10 aerosol samples were collected in the vicinity of the “Mario Zucchelli” Italian Antarctic Station (formerly Terra Nova Bay Station) during the 2000–2001 austral summer using a high-volume sampler and precleaned cellulose filters. The aerosol mass was determined by differential weighing of filters carried out in a clean chemistry laboratory under controlled temperature and humidity. A two-step sequential extraction procedure was used to separate the water-soluble and the insoluble (dilute-HCl-extractable) fractions. Cd, Pb and Cu were determined in the two fractions using an ultrasensitive square wave anodic stripping voltammetric (SWASV) procedure set up for and applied to aerosol samples for the first time. Total extractable metals showed maxima at midsummer for Cd and Pb and a less clear trend for Cu. In particular, particulate metal concentrations ranged as follows: Cd 0.84–9.2 μg g⁻¹ (average 4.7 μg g⁻¹), Pb 13.2–81 μg g⁻¹ (average 33 μg g⁻¹), Cu 126–628 μg g⁻¹ (average 378 μg g⁻¹). In terms of atmospheric concentration, the values were: Cd 0.55–6.3 pg m⁻³ (average 3.4 pg m⁻³), Pb 8.7–48 pg m⁻³ (average 24 pg m⁻³), Cu 75–365 pg m⁻³ (average 266 pg m⁻³). At the beginning of the season the three metals appear widely distributed in the insoluble (HCl-extractable) fraction (higher proportions for Cd and Pb, 90–100%, and lower for Cu, 70–90%) with maxima in the second half of December. The soluble fraction then increases, and at the end of the season Cd and Pb are approximately equidistributed between the two fractions, while for Cu the soluble fraction reaches its maximum level of 36%. Practically negligible contributions are estimated for crustal and sea-spray sources. Low but significant volcanic contributions are estimated for Cd and Pb (∼10% and ∼5%, respectively), while there is an evident although not quantified marine biogenic source, at least for Cd. The estimated natural contributions (possibly including the marine biogenic source) cannot account for the high fractions of the metal contents, particularly for Pb and Cu, and this suggests that pollution from long-range transport is the dominant source. Figure Aerosol sampling in Antarctica     

Determination of total and non-water soluble iodine in atmospheric aerosols by thermal extraction and spectrometric detection (TESI)

Iodine has recently been of interest in atmospheric chemistry due to its role in tropospheric ozone depletion, modification of the HO/HO₂ ratio and aerosol nucleation. Gas-phase iodine chemistry is tightly coupled to the aerosol phase through heterogeneous reactions, which are dependent on iodine concentrations and speciation in the aerosol. To date, the only method available for total iodine determination in aerosols is collection on filters by impaction and quantification by neutron activation analysis (NAA). NAA is not widely available to all working groups and is costly to commission. Here, we present a method to determine total iodine concentrations in aerosol impact filter samples by combustion of filter sub-samples (∼5 cm²) at 1,000 °C, trapping in deionised water and quantification by UV/Vis spectroscopy. Both quartz and cellulose filters were analysed from four separate sampling campaigns. The method proved to be sensitive (3σ = 6 ng absolute iodine ≈ 3 pmol m⁻³) precise (RSD ∼ 5%) and accurate, as determined by external and standard addition calibrations. Total iodine concentrations ranged from 10 pmol m⁻³ over the Southern Ocean to 100 pmol m⁻³ over the tropical Atlantic, in agreement with previous estimates. The soluble iodine concentration (extracted with water and measured by ICP-MS) was then subtracted from the total iodine to yield non-water-soluble iodine (NSI). The NSI fraction ranged from 20% to 53% of total iodine, and thus can be significant in some cases.     

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.     

Sulfur determination in coal by 14 MeV neutron activation analysis

A procedure involving the irradiation of coal samples with 14 MeV neutrons and subsequent gamma-ray spectrometry of the irradiated sample for the estimation of solfur in coal, has been outlined. The samples were irradiated with 14MeV neutrons from a Cockroft-Walton type generator for one minute and then subjected to gamma-ray spectrometry for another minute using an automated transfer cyclic system. Ten such cycles were repeated for accumulating events under the 2130 keV gamma ray photopeak belonging to³⁴P (T=12.4 s) produced by the³⁴S(n, p)³⁴P reaction for assessing the lower level of detection, LLD, of Sulfur. Interferences due to the presence of other elements in coal were also determined. Sulfur can be determined at LLD of 0.25% in coal provided a 5 g sample of the coal is irradiated with a neutron flux of 5·10⁹ n·cm⁻²·sec⁻¹ assayed with a gamma ray spectrometer having a large hollow core Ge(Li) detector and an anti-Compton shield.     

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’.     

Halogen speciation in the rat thyroid: Simultaneous determination of bromine and iodine by short-term INAA

The study describes a mode of non-destructive simultaneous determination of bromine and iodine concentrations, by reactor instrumental neutron activation analysis (INAA) in the regime of short-term activation. Under the conditions of 1-minute activation in the neutron flux of 8.0·10¹³ n·cm⁻²·s⁻¹, it was possible to determine reliably as little as 5·10⁻⁸ g bromine and about 10⁻⁷ g iodine in matrices of a given type and of the mass of about 5 mg dry weight. We applied this method for the determination of Br and I concentrations in the whole rat thyroid gland as well as for the halogen speciation in fractions separated from this organ.     

Direct determination of parts-per-billion levels of germanium in botanical samples and coal fly ash by graphite furnace atomic absorption spectrometry

 Parts-per-billion levels of germanium can be determined directly by graphite furnace atomic absorption spectrometry (GFAAS) using palladium plus strontium as a mixed modifier resulting in pyrolysis temperatures up to 1400 °C without loss of germanium. At this temperature the matrix effect including the most troublesome sulfate interference can be eliminated. Palladium plus strontium nitrate is advantageous compared to palladium alone or palladium plus magnesium nitrate; an amount of 15 μg of sulfate does not show any interference on the determination of 1 ng of germanium. The method was successfully applied to the determination of ng/g levels of germanium in botanical samples and coal fly ash after thermal decomposition of the samples in a mixture of acids using a pressure bomb. The results were consistent with the reference values given for botanical samples and coal fly ash with a recovery range of 96.4∼103.4% Received: 16 September 1996/Revised: 10 December 1996/Accepted: 14 January 1997     

Determination of uranium in liquid and solid samples by radioisotope excited XPR analysis using the ULα/ULγ ratio for matrix correction

A method for the exact determination of uranium in liquid and solid samples containing various main elements with Z≤29 is described. The method is based on simultaneous measurements of the excited LX fluorescent energies of uranium and the backscattered energies of the iodine target used for excitation. UL_α/UL_γ and (UL_υ/IK_αincoh)/U% peak intensities were found to be linearly dependent in samples of different chemical composition. Twenty eight liquid and solid samples of various matrices containing uranium in the range 0.3–30% were determined and a calibration line based on these measurements was obtained. Several samples containing different U concentrations were checked by this method and the average deviation of the calculated results from the known content is ±12.5%. The X-rays were excited using a 10 mCi²⁴¹Am/I source-target assembly and measured with 25 mm² Si(Li) detector.     

Measurements of electrical conductivity in solid bromine and iodine

Measurements of the electrical conductivity were performed with bromine and iodine in the liquid and the solid states, both containing low concentrations of the corresponding halide ions. In bromine the specific conductivity increases dramatically upon solidification and in iodine it changes only slightly. In both systems the conductivity in the solid is rather high, with remarkably low temperature coefficients, pointing to an unusual mechanism of conduction (of the Grotthuss type) requiring very little movement of the heavy nuclei while the charge is transferred. In mixtures of bromine with a small amount of nitrobenzene (NB) an equivalent conductivity as high as 12 cm² mol^?1 Ω^?1 was observed at ?25°C. In iodine the specific conductivity reached a value of about 0.01 Ω^?1 cm^?1 at 100°C. The energy of activation for conduction in bromine down to ?40°C was found to be about 23 kJ mol^?1, increasing sharply below this temperature. In iodine, values of about 21–27 kJ mol^?1 were observed over the whole temperature range measured.     

Determination of uranium,antimony, indium,bromine and cobalt in atmospheric aerosols using epithermal neutron activation and a low-energy photon detector

Owing to the high ratio of resonance integral to thermal neutron activation cross-section of²³⁸U, a 5 min epithermal neutron irradiation under cadmium shielding, followed by measurement of the 74 keV photopeak of²³⁹U with a high resolution low-energy photon Ge(Li) detector, allows the fast determination of uranium in aerosols collected on a Whatman 41 cellulose filter. Uranium blanks of the cellulose filter paper require correction and limit the sensitivity. Simultaneously the concentrations of the elements cobalt, bromine, antimony and indium can be determined. In Belgium, the uranium concentrations of the aerosols were found to be constant and comparable to the uranium contents of rocks.     

Study of mass transfer enhancement on liquid/liquid interface by flow instabilities using gallium liquid electrode

Abstrac  Using liquid gallium electrodes it was proved that electrodiffusion method is a convenient tool for measuring the mass transfer at liquid/liquid interface. It was shown that mass transfer coefficient at the liquid/liquid interface at high Reynolds numbers is much more important in comparison to that measured at the solid/liquid interface at identical geometrical and hydrodynamic conditions. In experiments with the flow induced by the rotation of the upper disc (working ring electrode is placed on the bottom of the immobile disc), the Sherwood number increases in turbulent regime as Sh ∼ Re^1.8 at the liquid/liquid interface, contrary to the traditional law Sh ∼ Re^0.9 at the solid/liquid interface. In laminar regime the Sherwood number at the liquid/liquid and at the solid/liquid interfaces follows the traditional dependence Sh ∼ Re^0.5. It was shown that sharp increasing of the mass transfer coefficient at the liquid/liquid interface is closely related with the appearance of the surface waves, the phenomenon is identified as a Kelvin-Helmholtz type instability. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 4, pp. 482–490. The text was submitted by the authors in English.