The determination of bromine and iodine in environmental water samples by thermal neutron activation and isotope exchange

A routine-method for the determination of bromine and iodine in environmental water by neutron activation is presented. The elements are isolated by isotope exchange between the irradiated sample and a solution of Br₂ or I₂ CCl₄. The method is not sensitive to the chemical species in which the halogen is present. The lower limit of the determination is 1.0 μg Br·1⁻¹ and 0.1 μgI·1⁻¹.     

Neutron activation determination of uranium by coprecipitation of neptunium-239 on zirconium phosphate

A method is proposed for neutron activation determination of U via²³⁹Np. This is separated by coprecipitation of ZrO(H₂PO₄)₂ and its 106 keV γ-peak measured. The sensitivity of the determination is 10⁻⁹ g. The method is based on the well-known ability of Np(IV) to coprecipitate with zirconium phosphate, while Np(VI) does not form insoluble phosphates or fluorides. This permits elimination of elements interfering, with the determination of²³⁹Np via the 106 keV γ-peak: Sm, Nd, Yb, Lu, Pa (from Th) and Ta. The rare earths are eliminated by coprecipitation on LaF₃, and Pa and Ta as insoluble phosphates in an oxidizing medium. The method is suitable for phosphorus-containing samples: phosphorites, apatites and their industrial treatment products. The results obtained for the uranium content with the proposed method are in good agreement with the results of other methods and authors.     

Zirconium as a multi-isotopic flux ratio monitor and a single comparator in reactor-neutron activation analysis

Different methods for the determination of thermal-to-epithermal neutron flux ratio are reviewed and nuclear data for commonly used monitor materials and for Zr isotopes are tabulated. It is shown that the use of the⁹⁴Zr−⁹⁶Zr isotope pair gives significant improvement in precision while measuring Φ_th/Φ_e ratios in the 20<Φ_th/Φ_e<200 range. When the single comparator method is applied, the use of the⁹⁴Zr isotope is suggested as a comparator with the⁹⁴Zr−⁹⁶Zr isotope pair for simultaneous flux ratio determination. Theoretical calculations show that the Zr comparator-flux ratio monitor gives better precision and accuracy than does Ru for two-thirds of the isotopes used for analysis in well thermalized (Φ_th/Φ_e>100) channels. The I_o/σ_th-values for the mentioned Zr isotopes have been experimentally determined and compared with previously published data. Research associate of NFWO.     

Neutron activation analysis of pure uranium: Preconcentration of impurity elements

We have developed a radiochemical neutron activation analysis technique (RNAA) of pure uranium with using extraction chromatographic separation of ²³⁹Np from impurity elements in TBP-6M HNO₃ media. The estimation of influence of fission products of ²³⁵U on the results by radiochemical neutron activation analysis has been carried out. For it we have performed NAA with preconcentration of impurity elements. Experiments show that in this case the apparent concentration of Y, Zr, Mo, Cs, La, Ce, Pr, Nd exceeds the true concentration by 2500–3000 times. Therefore, determination of these elements is not possible by RNAA. This technique allowed to use the determination of 26 impurity elements with detection limit 10⁻⁵–10⁻⁹% by mass. This developed technique may be used for the determination of impurities in uranium and its compounds.     

Possibilities of using simultaneous ion-induced nuclear and atomic activation for the characterization of hair

The possibility of a simultaneous determination of low and medium Z elements in hair in a single ion beam exposure was studied. Different ion beams, proton, deuteron,³He and¹⁸O, at velocities ranging from 2.7–6.9 MeV/amu were investigated. In this work,¹⁸ ₈O⁴⁺ beam was found to give the best experimental condition in terms of sensitivity and number of elements detected. The detection limits in a single hair ranged from 2.9·10⁻⁵ μg for Fe to 0.72 μg for H using this beam.     

Neutron activation analysis of the inorganic ions in Langmuir-Blodgett multilayers

An application of neutron activation analysis for the determination of inorganic ions in Langmuir—Blodgett multilayers is described. A special technique for the removal of multilayers from the solids substrate has been used. Multilayers of arachidic acid and octadecylamine are analyzed with respect to Cd²⁺ and HPO ₄ ²⁻ . Ca²⁺, Ba²⁺, Cu²⁺, HAsO ₄ ²⁻ , Cro ₄ ²⁻ and other ions can also be determined by means of this method. The results obtained are compared with those of other authors.     

The determination of fluorine in bones by non-destructive neutron activation analysis using 11.2 sec20F

A fast non-destructive determination of fluorine in bone samples by thermal neutron activation analysis using¹⁹F(n, γ)²⁰F reaction was developed. About 0.1–1 g samples is irradiated for 15 sec in TRIGA MARK II reactor at a thermal neutron flux of 5·10¹¹ n·cm⁻²·sec⁻¹. After 15–25 sec cooling, the 1633 KeV²⁰F activity (T=11.2 sec) is counted for 15 sec with a Ge(Li) spectrometer. A standard sample is prepared by mixing CaF₂ and CaCO₃ powders. The interference from²³Na(n, α)²⁰F is corrected by employing²⁴Na 2754 KeV double escape peak activities in samples and the²⁰F/²⁴Na peak area ratio observed previously for pure Na₂CO₃ powder. The precision is 7% for a bone sample containing 1020 ppm F and the sensitivity is about 10 ppm F.     

The determination of nickel in air dust by neutron activation analysis

The determination of nickel in atmospheric aerosols, collected on filter paper, is performed by thermal neutron activation analysis using the⁶⁵Ni (T=2.56 h) isotope. Liquid-liquid extraction and anion-exchange are applied in the chemical separation. The absolute sensitivity of the method is ≌0.02 μg Ni. The relative sensitivity is 0.005 μg Ni/m³ if an air sample of about 1000 m³ is used.     

Serum aluminum determination by instrumental neutron activation analysis in long-term haemodialysis patients

Serum aluminum levels were determined by instrumental neutron activation analysis in 31 patients undergoing long-term haemodialysis. Aluminum-28 1.778 MeV (T _1/2=2.24 min) γ-rays produced by the thermal neutron reaction²⁷Al(n,γ)²⁸Al were detected. Successive irradiation of the samples at epithermal neutron fluence was performed to correct for the interference from the fast neutron reaction³¹P(n,α)²⁸Al. Serum aluminum level in this group of subjects was adequately represented by a lognormal distribution with a mean and variance of 16.5 μg/l and 16.8 μg/l, respectively. The results obtained were found to be in agreement with serum aluminum determination performed by electrothermal atomic absorption spectrophotometry (r ²=0.97). Instrumental neutron activation can provide a rapid technique to routinely monitor long-term haemodialysis patients in order to identify individuals at greater risk to develop aluminum toxicity.     

The determination of inorganic arsenic in water by thermal neutron activation analysis

A simple method is presented for the determination of inorganic arsenic in water samples. The lower limit of determination is 0.01 μg·1⁻¹. Penta-and trivalent arsenic ions as well as arsenic acid substituted with aromatic ligands are collected by coprecipitation with Fe(OH)₃. After irradiation the arsenic is separated from the iron by adsorption to Al₂O₃. The overall efficiency is (97∓1)%. The procedure takes one day per ∼20 samples. It has been checked by standard addition. Data for sea- and surface-water are given. As the concentration of aromatic arsenic-compounds is very small in comparison to that of the inorganic species, it does not affect the result of the determination.     

The determination of tin in rocks by thermal neutron activation

A fast routine method for the determination of tin in rocks is discussed. The method is based on coprecipitation of tetravalent tin with ferric hydroxide, followed by a short irradiation in a high thermal neutron flux, extraction in toluene from 1∶1 sulphuric acid which is 5N in potassium iodide, and counting of^123mSn (T=40 m) or^125mSn (T=9.7 m) with a well-type NaI detector. In the present work^125mSn was used. The lower limit of determination is governed by the blank of the reagents. For a sample of at least one gram it is ≌ 0.2 μg Sn·g⁻¹.     

Nuclear and atomic activation with heavy ion beams

Heavy ion activation has been studied as a method for determining hydrogen. The reactions used [e.g.¹H(⁷Li, n)⁷Be] are the “inverse” of well known reactions [e.g.⁷Li(p, n)⁷Be]. Nuclear activation parameters for the ion beams of interest (⁷Li²⁺,¹⁰B²⁺) have been studied. The analytical feasibility is demonstrated with the determination of hydrogen in titanium at the 100 and 30 ppm levels with relative precisions of 8 to 10%. Detection limits in titanium are in the 0.1 to 0.5 ppm range. Heavy ion bombardment is also accompanied by the emission of characteristic X-rays (“atomic” activation). The parameters governing X-ray emission and background production have been investigated. Experimental K and L X-ray yields from thick targets have been measured for many elements excited by Oⁿ⁺ beams of 0.5 to 7 MeV/amu and Kr⁷⁺ beams of 0.5 to 1 MeV/amu. The simultaneous determination of trace elements at levels of 10 to several 100 ppm in microsamples (∼10⁻⁵ g) is demonstrated on biological specimens. K and L X-ray yields and corresponding detection limits have also been measured with the⁷Li²⁺ and¹⁰B²⁺ beams used for the nuclear activation of hydrogen. With these beams (∼6 MeV/amu) simultaneous nuclear and atomic activation is possible, yielding an unusual multielement trace analysis capability covering hydrogen and medium and high Z elements.     

Dosage non destructif de l’hafnium par activation neutronique et spectrometrie γ de179mHf et de178mHf (periodes respectives: 19.0 et 4.8 s)

A non-destructive method for the determination of hafnium in zirconium and various alloys, based on the formation of^178mHf and^179mHf, is proposed. For a neutron flux of 10⁹ n _th ·cm⁻²·sec⁻¹, the limit of determination is about 0.5 μg. This limit can fall to 50 ng with the multiple irradiation runs system (ten runs at 92-second cycles). The simple determination is complete within 15 minutes, whereas the multiple irradiation runs method requires about 15 minutes longer time.      

Determination of trace impurities in tin by neutron activation analysis

A method was developed for the determination of 15 trace elements in tin. High-purity tin samples (99.9999% and 99.999%) as well as tin of technical quality were analysed. Reactor neutron activation of the tin samples was followed by distillation of the matrix activities from a HBr−H₂SO₄ medium and Ge(Li) gamma-ray spectrometry of the distillation residue. The sensitivity of the method is generally high. For the high-purity samples the detection limits vary from 0.02 ppb (scandium) to 200 ppb (iron) for irradiation of 1 g of tin for 1 week at a thermal flux of 5·10¹²n·cm⁻². ·sec⁻¹. To decontaminate the surface of the tin samples, pre- and post-irradiation etching procedures were applied. The efficiency of these etching techniques was studied.     

Determination of silver traces in air by neutron activation analysis

A non-destructive system for determination of silver traces in air particulates collected on cellulose filters is described, based on neutron activation followed by¹¹⁰Ag β⁻ counting instead of the 657.7 keV γ-ray. The determination limit (for 10% confidence limit) is estimated to be about 10⁻⁹ g. The method is easily applicable to the determination of silver in cloud seeding experiments, since the filters themselves provide a consistent and fairly uniform source and samples are collected in general far from industrial areas, where the concentration of possible interfering elements in air is reasonably low.     

Flow injection spectrofluorimetric determination of iron(III) in water using salicylic acid

A simple and fast flow injection fluorescence quenching method for the determination of iron in water has been developed. Fluorimetric determination is based on the measurement of the quenching effect of iron on salicylic acid fluorescence. An emission peak of salicylic acid in aqueous solution occurs at 409 nm with excitation at 299 nm. The carrier solution used was 2 × 10⁻⁶ mol L⁻¹ salicylic acid in 0.1 mol L⁻¹ NH₄⁺/NH₃ buffer solution at pH 8.5. Linear calibration was obtained for 5–100 μg L⁻¹ iron(III) and the relative standard deviation was 1.25 % (n = 5) for a 20 μL injection volume iron(III). The limit of detection was 0.3 μg L⁻¹ and the sampling rate was 60 h⁻¹. The effect of interferences from various metals and anions commonly present in water was also studied. The method was successfully applied to the determination of low levels of iron in real samples (river, sea, and spring waters).     

Time-resolved chemiluminescent analysis of hydralazine in pharmaceuticals

A new analytical method is proposed for determination of hydralazine (HZ) in pharmaceuticals—measurement of the chemiluminescence (CL) emitted after reaction with phosphoric-acidified KMnO₄. The novelty of this method is the recording of the whole CL–time profile. Such a recording is possible by use of a CL-detector operating in tandem which enables the reactants to be mixed in the measurement cell only and, therefore, the CL is reaction monitored from beginning. At the precise time the pump is stopped signal recording is triggered and so CL evolution is recorded completely. The optimum chemical conditions for the determination were 0.8 mol L⁻¹ formaldehyde, 0.3 mmol L⁻¹ KMnO₄, 4.0 mol L⁻¹ H₃PO₄, and a total flow of 0.37 mL s⁻¹. Two calibration graphs were plotted, CL intensity and area under the profile curve against HZ concentration. Exhaustive statistical analysis provided very interesting results, for example, accordance with Clayton’s theory, detection limit below 0.2 μg mL⁻¹, and linear calibration ranges from 0.2 to 5.0 μg mL⁻¹. This method was successfully applied to the determination of HZ in pharmaceuticals. Because they are usually formulated in association with diuretics and β-blockers, the method was used for analysis of HZ in pharmaceuticals that contained either HZ only or HZ with other hypotensive substances. Obtained and nominal content were approximately the same and experimental Student t values indicated there were no significant differences between the values.     

Determination of chromium in blood by neutron activation analysis

A procedure for the determination of chromium in blood has been developed with a sensitivity of 5×10⁻³ μg Cr. Dried blood was irradiated with a neutron flux of 10¹² n·cm⁻²·sec⁻¹ in the VVRS reactor for 4 weeks, then the sample was mineralized and the chromium isolated by extraction as perchromic acid. The determination of the chromium content was accomplished by measuring the 0.32 MeV gamma energy of⁵¹Cr. In order to make correction for the interfering reaction⁵⁴Fe(n,α)⁵¹Cr, the formation of chromium from high-purity iron was investigated. The chromium content of the blood samples was between 1.03×10⁻² and 5.2×10⁻² ppm Cr.     

Spectrofluorimetric determination of uric acid based on its activation of catalytic oxidation of pyronine Y

A novel kinetic spectrofluorimetric method for the determination of uric acid based on the activation effect of uric acid on the Cu(II) ion catalyzed oxidation of pyronine Y by hydrogen peroxide was developed. The influence of different buffer solutions was tested and the Britton-Robinson buffer solution with pH 2.2 was found to be the optimum. The detection limit and the linear range for uric acid are 0.09 μg mL⁻¹ and 0.3–3.0 μg mL⁻¹, respectively. The RSD for eleven determinations of 1.6 μg mL⁻¹ uric acid was 1.6 %. Satisfactory results were obtained when using this method of uric acid determination in human urine.     

Determination of dysprosium,europium, samarium and gadolinium in yttrium oxide of high purity by means of neutron activation analysis

Radioactivation analysis is the only method which allows the determination of individual rare earth element impurities in rare earth elements of high purity. The determination of dysprosium, europium, samarium and gadolinium in yttrium oxide is complicated by the short half-life of¹⁶⁵Dy (138 min.) and by the difficulty of separating traces of these elements from the matrix. A chromatographic method has been developed, for the separation of traces of Dy, Eu, Sm and Gd from ytrium, on a column packed with anion exchangerAV-17, by means of elution with 0.1N and 0.3M solutions of EDTA-sodium salt, followed by the separation of the mixture of the rare earth impurities on a microcolumn of cation exchangerKU-2, using a 0.17M solution of ammonium α-hydroxyisobutyrate as the eluent. The sensitivity of the determination of Dy, in the case of irradiating 10 mg of Y₂O₃ with a flux of 1.2·10¹³ n·cm⁻²·sec⁻¹ for 5 min. was 1·10⁻⁷%; the corresponding values for Sm, Eu and Gd, when irradiating a 100 mg sample of Y₂O₃ for 20 hours with the same flux, were 2·10⁻⁷%, 1·10⁻⁸% and 5·10⁻⁶%, respectively.