Sorption of cesium and strontium ions on hydrous titanium dioxide from chloride medium

Epiboron instrumental neutron activation analysis (EINAA) using flexible boron as thermal neutron filter, has been used to analyze several salt samples obtained from various markets in Ghana for iodine. The method involves the irradiation of samples in boron carbide-lined polyethylene vials at the outer irradiation site of the Ghana Research Reactor-1 (GHARR-1). The samples were then counted directly without any pre-treatment on a Canberra N-type HPGe detector. The qualitative and quantitative analyses were done using the 443 keV photopeak of ¹²⁸I. The precision and accuracy of the method have been evaluated and the detection limits of the various samples were calculated. The values of iodine determined in the iodized salt range between 10.0 and 210 ppm. For non-iodinated salts, iodine levels were below 500 ppb. The values obtained show great variations among the salt samples, sample collection time and from market to market. This results show that the method can be successfully applied in the determination of trace amount of iodine in salt samples without any chemical separation.     

Rapid and accurate determination of thallium in seawater using SF-ICP-MS

We present a method for the rapid and direct determination of dissolved Thallium (Tl) using high resolution sector field inductively coupled mass spectrometry (SF-ICP-MS) suitable for the measurement of large time series (e.g. during monitoring). Thallium data are presented for a series of natural sea water samples, which were validated with sea water standards CASS-4 and NASS-5. The sea water samples and standards were diluted 10 times prior to measurement with SF-ICP-MS in low resolution mode (R = 300, LR). For both CASS-4 and NASS-5 (salinity of 30.5) we calculated a concentration of about 11 ng L⁻¹ when using Tl values of 14 ± 2 ng L⁻¹ (at salinity of 35 ± 1) published by Flegal and Patterson [1] for Atlantic and Pacific sea water. For CASS-4 we report a Tl value of 10.6 ± 0.7 ng L⁻¹ (n = 70), for NASS-5 a Tl value of 10.3 ± 0.8 ng L⁻¹ (n = 11). For Tl in both CASS-4 and NASS-5, the overall error in accuracy and precision is less than 4% and 8% (2 s), respectively. Further, values of 7.7 ± 0.3 and 6.7 ± 0.2 ng L⁻¹ Tl were found for the estuarine standard SLEW-3 (salinity of 15) and the river water standard SLRS-4, respectively, for which no certified value exists so far. The detection and quantification limits of our method are 0.1 and 0.3 ng L⁻¹, respectively. Slight differences in the accuracy of our method and other published methods for the determination of Tl in sea water are discussed. Time-series of natural coastal water samples gave Tl values (6-12 ng L⁻¹), which correspond to determined salinities, and hence, appear realistic and oceanographically consistent.     

In vivo neutron activation analysis of rats

A method of estimating total body calcium and sodium in rats by in vivo neutron activation analysis is described. The subjects were exposed to an integrated flux of about 1.6·10¹¹ thermal neutrons and activity was determined by counting with a 3″×3″ NaI(Tl) detector. The growth of the subjects was followed for about 75 days. The values of total body concentrations obtained are 0.83–0.90% for Ca and 0.128% for Na. Consideration is given to the accuracy attainable and to the effects on the blood and the hematopoietic tissues of the radiation doses imparted.     

Use of a nitrate-form anion exchange resin for the determination of traces of gold in copper and cadmium by neutron activation analysis

A method is described for the determination of traces of gold in copper and cadmium by neutron activation analysis, using anion exchange resin as a preconcentration agent: gold was separated from large amount of copper or cadmium with Cl-form Dowex 1X8 AG, 100–200 mesh, resin. To reduce the interfering activities, the resin was irradiated in NO ₃ ⁻ -form and washed with dilute hydrochloric acid after irradiation.¹⁹⁸Au in the resin was then counted with a Ge(Li) or NaI(Tl) detector. The chemical yields were more than 99%. The concentration factors of gold for copper and cadmium samples were 1.1×10⁸ and 2.7×10⁶, respectively. The analytical results of gold in 99.99% copper and 99.999% cadmium were 65 and 0.15 ppb, respectively. The blank was 0.05 ng Au per 200 mg of wet resin.     

Activation analysis of gallium in tungsten

An activation analytical method is described for the determination of small concentrations of Ga in tungsten. The samples are irradiated with reactor neutrons and dissolved in a hot chamber using a remote manipulator. After the adjustment of thepH, Ga is extracted in the form of its cupferron complex in chloroform solution. The organic phase is washed and, depending on the efficiency of the separation from tunsgten, a Ge(Li) semiconductor detector, or a NaI(Tl) scintillation counter is used for the gamma-spectrometric evaluation. The sensitivity of the method for a sample of 2 g was found to be 10⁻⁹ g of Ga/g of W. The determination can be carried out, and is well reproducible, with an accuracy of ±30%.     

Instrumental neutron activation analysis of manganese in some industrially important steel samples

The manganese content of some industrially important steel samples viz. IS-226, spring steel, galvanized iron, high tensile steel, and mild steel is determined by instrumental neutron-activation analysis using a²⁵²Cf neutron source. The analysis is performed by measuring the activity of⁵⁶Mn after /n, / reaction on a 4 k multichannel analyzer coupled to a NaI/Tl/ detector at 847 keV, as well as on a single channel analyzer on integration mode coupled to a NaI/Tl/ detector. The results obtained by both procedures show reasonably good agreement with each other.     

Rapid determination of90Sr by Compton suppression gamma-ray spectrometry

This work presents a low-level background gamma spectrometry system capable of achieving rapid determination of⁹⁰Sr without chemical separation, in a soil sample when the⁹⁰Sr to -ray emitting nuclide concentration ratio exceeds 10. The system consists of a highly efficient HPGe central detector operated in coincidence or anticoincidence with a NaI(Tl) guard detector and a NaI(Tl) backscatter detector. Experimental results indicate that the bremstrahlung radiation from a pure -emitter can be distinguished with respect to the differences in normal and coincidence spectra. The⁹⁰Sr activity can be directly detemined in the sample in less than 1 hour with a minimum detectable concentration (MDC) estimated at 0.002 Bq·g^–1 for a sample containing no appreciable -ray nuclides or other high energy, -emitting nuclides. In actual measurement, a 0.06 Bq·g^–1 MDC for contaminated soils is achieved.     

Crystal detector calibration for large sample counting

A useful method for crystal detector calibration by using point sources is presented. The method is applied to determine the total efficiency of a 80×80 mm NaI/Tl/ crystal in an energy window suitable for¹³⁴Cs+¹³⁷Cs activity evaluation in a sample of 750 cm³.     

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.     

A method for quick estimation of129I by low energy photon spectrometry

Methods have been developed for the routine analysis of¹²⁹I in effluents of fuel reprocessing plants using 29.4 keV xenon X-rays. Direct counting methods have been standardized in liquid medium as well as in ion-exchange resin medium. A low energy photon spectrometry Ge detector system and a well-type NaI/Tl/ detector are used for direct counting. Attenuation of xenon X-rays in liquid medium as well as in ion-exchange resin medium have been studied. Sample size is optimized by studying the self attenuation of xenon X-rays in the sample. Activity as low as 1 Bq could be detected with an accuracy of 11% and 30% using LEPS and NaI/Tl/counting systems, respectively.     

Epithermal instrumental neutron activation analysis for the determination of gold and arsenic in Ghanaian gold tailings using conventional and anti-coincidence counting

Epithermal instrumental neutron activation analysis (EINAA) together with both conventional and anti-coincidence counting techniques were used to analyze six different gold tailing samples from Ghana for Au and As. The method involves the use of the epi-cadmium site of the Dalhousie University Slowpoke-2 reactor facility for the irradiation of the samples. After irradiation, the samples were counted directly on the detectors. The identification and quantification of the elements were done using 411 keV photopeak of ¹⁹⁸Au and both 559 keV and 657 keV photopeaks of ⁷⁶As. The precision and accuracy of the method were evaluated. Values for Au in the samples ranged from 2.48 ppm and 6.76 ppm and for As between 1,550 ppm and 3,460 ppm. The values obtained using the two counting systems were in good agreement while the anti-coincidence counting system gave values of higher precision and accuracy. The detection limit for Au were 20 and 10 ppb for the conventional and anti-coincidence spectrometric systems, respectively, and 50 ppb for As in both cases. Details of the method and results are presented.     

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.     

Semiquantitative Analysis of Biological Materials by Inductively Coupled Plasma–Mass Spectrometry

Semiquantitative analysis with accuracy of ±30 to 50% is a valuable tool for rapid screening of samples prior to quantitative determination of trace metals. In this study semiquantitative analysis software available with commercial inductively coupled plasma–mass spectrometry (ICP-MS) instrumentation is applied for rapid multielemental analysis, and the accuracy and precision of this semiquantitative analysis approach is evaluated with biological certified reference materials. Samples were prepared by high-pressure, high-temperature nitric acid vapor-phase digestion. For most elements the measured semiquantitative results are in the range of the certified values. With appropriate analyte solution dilution, the measured concentrations of the major elements (e.g., Ca) also agree with certified values. The accuracy is within ±10% for 28 element determinations that include 16 individual elements (Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rb, Sb, Sr, Tl, and Zn) and ±20% for 54 element determinations that include three more elements (Mg, V, and U) in eight certified reference materials including water. The method precision is 11 ± 11% (relative standard deviation,n= 65).     

Determination of traces of ruthenium by neutron activation analysis using a polyethylene film

A neutron activation analytical method is described for the determination of traces of ruthenium. Acid solution of an inorganic chemical or seaweed ash is heated in a conical flask with oxidants, ruthenium ingredient is distilled and fixed on a polyethylene film, which is placed on the top of the flask. Many films were irradiated together in a thermal neutron flux, and after about a month γ-ray peak counts under the 497 keV peak of¹⁰³Ru were measured with a well-type NaI(Tl) or a Ge(Li) detector. In the chemicals of fifty one elements, compounds of four platinum metals were contaminated with 2100-150 ppb Ru, and Ga, In, Tm, Tb, Yb: all trivalent elements contained 510-16 ppb Ru. The ruthenium content of all other chemicals were of ppb order or less. In these, Ga, In, Tm and Yb were known as scintigram elements of cancer. In the ash of Porphyra tenera 2 ppb Ru was detected. A part of this work was done under the Visiting Researchers Program of Kyoto University Research Reactor Institute.     

Natural radioactivity levels of limestone rocks in northern Iraq using gamma spectroscopy and nuclear track detector

The activity concentration of radionuclides, such as ²³⁸U, ²²⁶Ra and ⁴⁰K of limestone rocks in northern Iraq was measured using gamma spectroscopy. The radionuclide activities were obtained and discussed. CR-39 nuclear track detector was used to measure the radon exhalation rates as well as the effective radium contents of these samples and are found to correspond with uranium concentration values measured by NaI(Tl) detector in the corresponding limestone rocks samples. The absorbed gamma dose rates in air due to the presence of ²³⁸U, ²²⁶Ra, ⁴⁰K and cosmic ray contribution varied between 105.3 and 223.11 nGy/h. The annual effective dose of each sample has been calculated. The correlation between activities of ²²⁶Ra, ²²²Rn exhalation rates and ²³⁸U is explained. Results show a symmetrical distribution of activity concentrations of primordial of radionuclides in selected samples. The values of all studied radionuclides are considered to be a typical level of natural background and compared with results of similar investigations carried out else where.     

Determination of chlorine distribution in silicon dioxide by neutron activation

A neutron activation method for the determination of chlorine distribution in silicon dioxide on the surface of Si wafers has been developed. After irradiation of the sample with a standard, successive layers are removed from the oxide surface by chemical etching and the chlorine content in the solutions obtained is determined gamma-spectrometrically. Using a Ge(Li) detector, a lower limit of determination of 1.0·10⁻⁷ g was obtained. This limit can be improved by using a NaI(Tl) detector. The error of chlorine determination is discussed.     

Method Validation for Determination of Thallium by Inductively Coupled Plasma Mass Spectrometry and Monitoring of Various Foods in South Korea

Thallium (Tl) is a rare element and one of the most harmful metals. This study validated an analytical method for determining Tl in foods by inductively coupled plasma mass spectrometry (ICP-MS) based on food matrices and calories. For six representative foods, the method’s correlation coefficient (R²) was above 0.999, and the method limit of detection (MLOD) was 0.0070–0.0498 μg kg⁻¹, with accuracy ranging from 82.06% to 119.81% and precision within 10%. We investigated 304 various foods in the South Korean market, including agricultural, fishery, livestock, and processed foods. Tl above the MLOD level was detected in 148 samples and was less than 10 μg kg⁻¹ in 98% of the samples. Comparing the Tl concentrations among food groups revealed that fisheries and animal products had higher Tl contents than cereals and vegetables. Tl exposure via food intake did not exceed the health guidance level.     

Design and evaluation of a TNA explosive-detection system to screen carry-on luggage

Thermal neutron analysis (TNA) technology has been used for the non-destructive detection of explosives. The system uses a relatively weak ²⁵²Cf neutron source (1.03·10⁷ n/s) and two 3"×3" NaI(Tl) detectors. The presence of explosives is confirmed via detection of the 10.83 MeV prompt gamma-ray associated with nitrogen decay. The MCNP4A code was used to simulate the neutron and gamma transport through the system. The thermal neutron flux in the activation position was measured using gold and indium foils. The measured thermal neutron flux was lower, by not more than 9.5%, than that of simulation. In this report the results of the preliminary tests on the system are described.     

Neutron activation analysis of manganese and nickel in commercial steel samples

The non-destructive thermal neutron activation analysis of some commercially available steel samples viz. SS-316, SS-310, SS-304, Tiscral, CA55 and EN 8 is carried out using a²⁵²Cf source. The manganese content of these steel samples is estimated by measuring the -activity of⁵⁶Mn using a single channel analyzer on integration mode and a NaI/Tl/ detector as well as using a high purity germanium detector coupled to a 4K multichannel analyzer. The results obtained by both procedures show reasonable agreement with each other. The nickel content of the various steel samples is also estimated.     

A simple method for the activation analysis of mercury in fish by using iodinated resins

After irradiation and decay periods, samples are dissolved in 20 min in a sulfuric-nitric acid mixture containing a metavanadate salt. The aqueous phase is neutralized and passed through an iodinated resin which selectively isolates mercury from all other interfering radionuclides. The activity of¹⁹⁷Hg is determined by γ-spectrometry using a thin Na(Tl) detector. A sensitivity limit of 2.5 ppb^* is obtained and the relative standard deviation of the method is 6.7% at a level of 85 ppb.