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.     

The rapid determination of silver to silver plus copper ratios in coins using 14 MeV neutron activation analysis

A non-destructive method for the analysis of the silver to silver plus copper ratio in coins using 14 MeV neutron activation analysis has been studied. The mass of silver to the mass of copper is obtained by measuring the 0.511 MeV annihilation radiation emitted by⁶⁴Cu and¹⁰⁶Ag at two separate times after irradiation. A series of British silver three-penny pieces dated 1891–1941 were analysed and agreed well with the mint assay. The interference from the presence of zinc in some coins was investigated.     

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.     

INAA of Zr,La, Ce and Nd in geological samples in the presence of different uranium concentratios

Rock samples which contain relatively high concentrations of uranium may create problems of interference produced by fission products, when instrumental neutron activation analysis is used. The isotopes⁹⁵Zr,¹⁴⁰La,¹⁴¹Ce, 143Ce and 147Nd, which are commonly used in the neutron activation analysis of the corresponding elements, are also produced as fission products of²³⁵U. For each of these radioisotopes, a contribution factor is calculated theoretically and meaured experimentally using geological samples with different uranium contents.     

A rapid radiochemical procedure for uranium determination in natural waters

A neutron activation analysis method for the determination of uranium in natural fresh waters is described. The method is based on a preconcentration step by precipitation of the metal oxinate on a phenolphtalein bed followed by instrumental neutron activation analysis. Preliminary investigations with²³⁹U radiotracer were carried cut to set up the best working conditions and to evaluate the chemical yield. The whole procedure has been applied to the determination of uranium in river water.     

Comparison between two INAA methods applied to chemical characterization of ancient ceramics

Two different instrumental neutron activation analysis (INAA) methods were applied to characterize chemically 74 ceramic roof tile samples, found in the town of Pella, Greece and dated back to the Hellenistic Period (3rd century B. C.). The samples were first analyzed for 17 elements with a 4 hour irradiation and two counts and then re-analyzed for 9 elements with a 1 minute irradiation and two counts of short-lived radioisotopes. The results of both methods were very similar, showing the validity of the rapid INAA method (1 min irradiation) in the study of ancient ceramics. All samples were divided into 4 chemical groups, each one representing a different tiling.     

Performance of NAA Methods in an International Interlaboratory Reference Material Characterization Campaign

An extensive database of analytical results from a recent biological matrix Reference Material Characterization Campaign permitted an intercomparison of the performances of various methods among each other and with "true" best estimate concentration values established for these materials. Six different variants of neutron activation analysis (NAA) methods were employed including: instrumental neutron activation analysis, instrumental neutron activation analysis with acid digestion, neutron activation analysis with radiochemical separation, neutron capture prompt gamma activation analysis, epithermal instrumental neutron activation analysis, and neutron activation analysis with preconcentration. The precision and accuracy performance of NAA-based analytical methods are compared with three other major techniques, atomic absorption spectrometry (AAS), atomic emission spectrometry (AES) and mass spectrometry (MS) for 28 elements in 10 natural matrix materials.     

Neutron activation analysis of cadmium in Jamaican soils

A procedure for the instrumental neutron activation analysis of Cd in soils with relatively high Cd content and possible inteferences is reported. Cadmium concentrations in Jamaican soils above 4 mg·kg⁻¹ can now be reliably determined by multielemental instrumental activation analysis with an accuracy ±10% and the reasonably high throughput of 30 samples per day. Over 600 geochemical survey samples were analysed for Cd along with some 20 other long-lived elements.     

Practical aspects of neutron activation determination of the platinum metals

Triple gamma coincidence counting of¹⁹²Ir allowed the determination of Ir by instrumental neutron activation analysis down to 1 ppb in ultrabasic rocks and down to ca. 20 ppb in some high-furnace slags; the limiting factor for the latter matrix was the presence of¹²⁴Sb. Radiochemical neutron activation analysis of the USGS standard rocks revealed that the Ir contents are up to three orders of magnitude lower than previously reported, except for the ultrabasic rocks. The factor of merit of several scintillation and semiconductor, gamma-ray detectors was determined for the neutron activation determination of Pd, Pt and Os. In the case of radiochemically pure sources, a NaI(Tl) wafer was preferred; in the presence of high-energy gamma-emitters, a Ge(Li) low-energy photon detector was superior.     

Multielement analysis of archaic Chinese bronze and antique coins by fast neutron activation analysis

Samples of archaic bronze have been investigated by fast neutron activation analysis using both the absolute and relative method. The components Cu, Zn, Sn and Pb have been determined quantitatively. For the detection of lead via the short-lived isomeric state^207mPb, cyclic activation and measurement technique was used with pneumatic sample transfer between detector and central irradiation position of the neutron tube. For nondestructive analysis of antique Chinese coins the samples had to be irradiated outside the neutron generator KORONA. The activation reactions, the evaluation of the elemental concentrations and the accuracy of the results are discussed. The data were corrected for -ray self-absorption in the samples and summing of coincident -rays in the detector. According to reported typical compositions of Chinese bronze from different dynasties, the age of the samples has been derived from the results obtained.     

Errors in instrumental neutron activation analysis based on short-lived radionuclides

Accuracy and precision of instrumental neutron activation analysis, based on short-lived radionuclides, are considered. Equations are derived for both quantitives as a function of concentration and features of the γ-ray spectrum. The determination of vanadium by way of⁵²V(T=3.75 min) is used as an example.     

An automated neutron activation system for short-lived nuclides

The present paper describes an attempt to create a reliable and easy to use system for neutron activation with short-lived nuclides, suitable to be used with several irradiation and counting procedures in instrumental neutron activation analysis (INAA) at the Portuguese Research Reactor. This system can become very useful for a large community within LNETI, as well as other national institutes and universities, particularly for those involved in studies where the analysis of a large number of samples is required. Selenium determination has been performed, through the short-lived nuclide^77mSe, as an example of the reliability of the system.     

Practical aspects of simultaneous determination of selenium and ytterbium by neutron activation analysis

An instrumental method for the simultaneous determination of selenium and ytterbium by thermal neutron activation analysis is described. Selenium and ytterbium were determined via the 400.7 keV photopeak of⁷⁵Se and the 177 keV photopeak of¹⁶⁹Yb. The accuracy of this instrumental method has been examined; as a result, it has been proved that this method is most exact and accurate when the gamma-ray counting is carried out after the decay of¹⁷⁵Yb.     

Measurement of calcium and titanium from 47sc by instrumental neutron activation analysis

A procedure is outlined for measuring calcium and titanium from ⁴⁷Sc by instrumental neutron activation analysis. Precise calcium measurements obtained from ⁴⁷Sc are compared with measurements based on ⁴⁷Ca and ⁴⁹Ca. The method is particularly suitable for low levels (ca. 1%) of calcium.     

Comparison between the minimum detection limits of radioisotope X-ray fluorescence technique and activation analysiś with a low intensity252Cf neutron source

A comparative study of radioactive X-ray fluorescence and neutron activation analysis using a low-intensity²⁵²Cf source has been carried out. X-ray fluorescence proved to be superior to NAA if ion-exchange preconcentration preceds the instrumental method, while less difference in the minimum detectable limit was found in direct analysis of aqueous solutions.     

Arsenic speciation: HPLC followed by ICP-MS or INAA

Sensitivities for the measurement of four arsenic species, As^III, As^V, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), in environmental waters and rice extracts by a new neutron activation analysis (NAA) method using pre-separation of the species by liquid chromatography were determined. A manual fraction collection was used to isolate the species, followed by instrumental neutron activation analysis procedures. The sensitivities determined for arsenic species in the samples varied from 1.21 to 1.47 ng per vial or about 30 μg·L⁻¹ in sample solutions which translates to about 900 ng arsenic per gram of rice for our HPLC-NAA experiments.     

Multielement analysis of lichen by instrumental neutron activation analysis

Lichen (species Trypethelium Eluteriae) is analysed for different elements. Nondestructive instrumental neutron activation analysis is employed for the multielemental analysis. Gamma-ray spectrometry is used for the identification and quantitative estimation of elements. Concentrations of 24 elements are reported. Gamma-ray spectrum of the lichen irradiated for 16 hours, delayed for 10 days, and counted for 10 hours on a 50 cm³ coaxial Ge(Li) detector is given.     

Studies on iridium and platinum determination in metallic rhodium by NAA and CPAA

The determination of Ir and Pt in rhodium neutron monitors was investigated via¹⁹²Ir and¹⁹⁹Au after neutron activation, via¹⁹¹Pt and¹⁹⁴Au–¹⁹⁶Au after proton activation. Ir was determined by instrumental NAA. A chemical separation of gold, with a yield measurement method by a radioactive tracer, was developed for platinum determination after neutron or proton irradiation.     

Precocentration method using an activatable yield tracer for neutron activation analysis

Previously, the use of an enriched stable isotope as an activatable yield tracer in preconcentration steps has been tested by use of commercially available enriched¹¹⁶Cd and¹⁵⁶Dy for biological standard reference materials.^1,2 In the present work, this method has been further applied to the determination of lanthanoid contents in various kinds of samples: one coal fly-ash, three Japanese standard rocks, and eight standard soils. Samples were decomposed by alkali fusion in the preconcentration step. Thirteen elements were determined for coal fly-ash and soil samples, and 14 elements for rocks. The data obtained for coal fly-ash and standard rocks are compared with the data reported in literature. The data for soil samples have been newly determined in the present work. The ordinary instrumental neutron activation analysis and radiochemical neutron activation analysis were also performed to confirm the accuracy and usefulness of the present method.     

The determination of vanadium in geological materials by activation analysis with pre-irradiation separation

Vanadium is determined in silicate rocks by neutron activation after dissolution of the samples with HF/HNO₃ and separation by solvent extraction. The chemical yield of the pre-irradiation separation is determined by means of ⁴⁸V tracer. Results for 15 U.S. Geological Survey standard rocks are presented and discussed in relation to literature data. The method is especially useful at vanadium concentrations below 10 ppm, where purely instrumental neutron activation as well as other techniques commonly used for vanadium determinations in rocks, have inadequate sensitivity.