A neutron activation procedure for the determination of dissolved silver in sea water

A neutron activation procedure has been developed for the determination of silver in sea water. The element is preconcentrated by an anion-exchange procedure. The concentrate is submitted to irradiation with thermal neutrons. Silver-11Om is separated from other radionuclides by means of a conventional radiochemical separation scheme. The method gave a coefficient of variation of ± 10% at a silver level of 40 ng l^?1.     

Determination of the silver content of ancient silver coins by neutron activation analysis

A reactor neutron activation analysis procedure for the determination of the silver content of silver coins is described. The samples are irradiated for 1 s, cooled for 85 s and measured for 60 s with a Ge-detector. The analysis is based on the measurement of¹¹⁰Ag and¹⁰⁸Ag. Aluminium is used for flux monitoring and pulse pile-up correction. A calibration curve is prepared by irradiating and measureing a series of discs with known silver contents. An average precision of ±2.1% is obtained. The analysis of coins with known silver contents shows good agreement with the given values. The analysis time is 2.5 minutes per sample.     

Performance of flowing sample neutron activation analysis technique for determination of multi-elemental content

In order to measure and obtain reliable data about elements via measuring of short-lived isotopes in liquid samples using neutron activation analysis, experiments have been carried out using a flowing sample neutron activation analysis method. During this work the performance and reliability for the proposed method have been tested using synthetic multi elements liquid samples. The radionuclide, associated elements and their concentration level have been measured using a counting system with a fixed dead-time. An HPGe spectrometry system was used to determine the most important γ-ray energies and intensities of these isotopes. The obtained results demonstrated the reliability and accuracy (bias <5 % and zeta score <2) of the tested method for determination the elemental content of liquid samples.     

Substoichiometric determination of tungsten by neutron activation analysis

A method for the substoichiometric determination of tungsten by thermal neutron activation analysis has been developed based on the selective extraction of the tungsten dithiol complex into amyl acetate. The method is simple, rapid and accurate. It has been used in the determination of tungsten in alloy steel, meteorites and biological standard kale.     

Substoichiometric determination of gold by neutron activation analysis

A rapid method has been developed for the determination of gold in catalyst samples by thermal neutron-activation analysis incorporating substoichiometric solvent extraction of Au/III/ with 1,2,3-benzotriazole /1,2,3-BT/ into n-butanol. The time required for radiochemical purification and counting of two samples and a standard was 1 h.     

Substoichiometric determination of Cd by neutron activation analysis

A rapid method has been developed for the determination of cadmium in environmental samples by thermal neutron activation analysis involving substoichiometric extraction with 1,2,3-benzotriazole /1,2,3-BT/. Cd was radiochemically separated as CdS using 1-amidino-2-thiourea. The time required for radiochemical purification containing two samples and a standard was about 2 h. 4.63 g of Cd can be determined with an accuracy of 6.69% and precision of 6.25%. Mash potatoes, animal bones, raw sludge and cattle manure have been analyzed by this method.     

Substoichiometric determination of palladium by neutron activation analysis

A method is described for the substoichiometric determination of traces of palladium by neutron activation analysis involving the extraction of palladium with isonitrosoacetophenone. The sensitivity of the method is 0.005 μg of Pd. With 200 mg of silver alloy containing 0.0005% palladium, the average of three determinations of Pd is 0.98 μg, which varies between 1.07 μg and 0.91 μg at 95% confidence limit. The time required for radiochemical purification and counting of the sample does not exceed 12 minutes. Part of this work was presented at the International Conference on Modern Trends Activation Analysis, held in Gaithersburg, Maryland, USA, October 7–11, 1968.     

Substoichiometric determination of mercury by neutron activation analysis

A method has been developed for the substoichiometric determination of mercury by thermal neutron activation analysis, based on the selective extraction of the Hg(II)—Bindschedler's Green complex into 1,2-dichloroethane. The method has been applied for the determination of trace amounts of mercury in geological standards such as W-1, GR, Sye-1, and T-1, meteorite Allende de Publito, and biological materials such as kale, IR1 standard tobacco, and human blood serum.     

Substoichiometric determination of chromium by neutron activation analysis

A method of radioactivation analysis has been developed for the determination of chromium. It is based on the substoichiometric extraction of chromium diethyldithio-carbamate into methyl-isobutyl-ketone from acetate buffer solution in the presence of EDTA and potassium cyanide. The method has been applied for the determination of chromium in high-purity calcium carbonate and NBS glasses as standard reference materials.     

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.     

Non-destructive examination of roman silver coins by neutron activation analysis

The detection of “plated” specimens (ancient falsifications consisting of a copper core with a silver outer layer) amidst a great collection of silver coins was performed by non-destructive neutron analysis. The “plating” can be detected by measuring the Ag/Cu ratio. In practice it is more convenient to determine the Au/Cu ratio which is proportional to it, A short activation in a low thermal neutron flux is sufficient for this purpose. Consequently the induced activity of the long-lived^110mAg is small. The necessary correction for self-absorption on the measured ratio is small. A series of 2000 coins was analysed in this way.     

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.     

The simultaneous determination of silver,gold and mercury in high-purity lead by neutron activation analysis

A radiochemical method was developed to separate the group of the noble metals simultaneously from a lead matrix after irradiation with thermal neutrons. The resulting complex γ-spectrum was resolved by matrix calculus. Smoothing of the obtained data to determine the presence of small photopeaks among the background fluctuations, was done by convolution, based on a least squares approximation. The interference of antimony and bromine was studied. Amounts as low as 20–30 p.p.b. of Hg and less than 1 p.p.b. of Au were determined in the presence of up to 9 p.p.m. of Ag.     

Multielemental determination in water by neutron activation analysis

Instrumental neutron activation analysis (INAA) technique has been applied to a water sample to determine the elemental concentrations. The sample was irradiated at a neutron flux of 1.2·10¹² n·cm^–2·s^–1 for two different periods followed by counting at three different decay times, using two coaxial type high-resolution Ge(Li) detectors. The dominant elements detected in the water sample are Ca, Cl, Na, Mg, and K present in levels while Co, I, Mn, Sm, and Sb are present in smaller amounts approximately on the average 0.01 ppm. Only traces of other elements such as rare-earth elements, Ag, As, Ba, Cu, Cd, Fe, Sr, W, Zn, seem to be present in the water samples.     

Substoichiometric determination of Hg by radiochemical neutron activation analysis

A rapid method has been developed for the determination of mercury in environmental samples by thermal neutron activation analysis. Radiochemical separation involves the extraction of Hg/II/ with substoichiometric amounts of 2-mercaptobenzothiazole /2-HMBT/ into chloroform¹. The time required for radiochemical purification and counting of two samples and a standard is about 2 h. Water, sludge and IAEA standard samples were analyzed for Hg concentration by this method.     

The determination of sampling constants by neutron activation analysis

It has been found that sampling constants vary greatly not only from major elements to trace elements, but also between individual trace elements. A comprehensive investigation of a potential reference material therefore requires the determination of sampling constants for all elements to be certified, and other analytical methods therefore have to be included. For methods in statistical control the described strategy can be applied.     

A technique for improved detection limit in indirect neutron activation determination of boron

Using vanadium as the activable element, an indirect cyclic neutron activation technique for determination of boron in aqueous solutions has been developed. Experimental arrangement consisted of a 5 Ci Pu?Be based neutron irradiator and a 7.5 cm × 7.5 cm NaI/Tl/ detector. Recycling of vanadium between the irradiation source and the detector produced improved detection limit and sensitivity.     

A neutron activation technique for the isotopic analysis of rhenium in the subnanogram-region

Résumé On applique l'activation neutronique aux mesures d'abondance isotopique du rhénium dans les matériaux lunaires. On y parvient en comparant les activités induites par (n, γ) de¹⁸⁶Re et¹⁸⁸Re au moyen des raies γ de respectivement 137 et 155 keV. Afin d'éviter les interférences, (spécialement celles de¹⁹⁹Au et^99mTc) on a besoin d'un procédé conduisant à une grande pureté radiochimique. De plus, on détermine les teneurs en rhénium et tungstène. On a remarqué une anomalie isotopique du rhénium dans les échantillons d'Apollo-14, montrant un enrichissement remarquable en¹⁸⁷Re (de 1,4 à 1,8% dans les sols et jusqu'à 29% dans les brèches). On montre enfin que cet enrichissement est partiellement d? à l'irradiation neutronique sur la surface lunaire par la réaction¹⁸⁶W(n,γ)¹⁸⁷W ¹⁸⁷Re. Cependant, l'anomalie observée, causée principalement par les neutrons intermédiaires, n'est pas produite uniquement par les neutrons lunaires. L'activation d'un réacteur y contribue aussi par la réaction:¹⁸⁶W(n,γ)¹⁸⁷W ¹⁸⁷Re(n,γ)¹⁸⁸Re, qui peut être corrigée par l'analyse d'étalons de tungstène irradiés simultanément. On estime que la contribution lunaire à l'enrichissement du¹⁸⁷Re est de 20 à 60% de l'excès total observé.      

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.     

Substoichiometry in neutron activation analysis technique

Neutron activation analysis has become one of the most sensitive and selective analytical technique for the determination of trace elements in a wide variety of matrices. Neutron activation involves the irradiation of the test sample and a standard of the element to be determined with thermal neutrons in a reactor, followed by dissolution of the test sample in the presence of carrier of the element to be determined. The carrier and radioisotopes are separated from the bulk of other induced activities (employing precipitation, solvent extraction, ion exchange etc.) and then the activity induced in the sample is measured on a suitable detector. The standard is treated identically. From the ratios of the activity of the sample and standard and the weight of the standard irradiated, the concentration of element in the test sample is calculated. A rapid, selective and sensitive method of radiochemical separation is subtoichiometric extraction in which the same amount of carrier is added to the irradiated test sample and standard. Exactly the same amount of reagent is added to both the sample and standard but in substoichiometric amounts, followed by the separation of the species formed by extracting it with an organic solvent. The activities of the extracts are measured. The amount of element present in the sample is calculated with help of the ratio of the activities and the weight of the standard taken. The advantages of the method are discussed. Application of substoichiometry in neutron activation has been elucidated with reference to the determination of Au in various samples by substoichiometric neutron activation analysis.