Determination of selenium in individual food items using the short-lived nuclide77mSe

The selenium content of a variety of food items representing a normal hospital diet has been determined by cyclic instrumental neutron activation analysis (CINAA) through the 162-keV gamma-ray of the^77mSe nuclide. The CINAA method is very simple and rapid. It involves irradiation of a sample for 20 s, decay for 20 s, and counting for 20 s. The precision of the method has been significantly improved by recycling the samples up to 4 times. The accuracy has been evaluated by analyzing a number of certified reference materials of varied selenium levels.     

Determination of mercury by radiochemical displacement

2–15 g of mercury has been determined by exchange with zinc in⁶⁵Zn labelled zinc sulphide. The influence of various ions which are likely to interfere in the determination of mercury has also been studied.     

Determination of chromium in biological reference materials by instrumental NAA using Compton suppression

Instrumental neutron activation analysis in conjunction with Compton suppression methods has been used to determine chromium concentrations in 13 biological reference materials. Special attention was focussed on the interferences and the ways of lowering their contribution. Separate data was obtained for normal and Compton suppressed modes of counting so that a comparison could be performed. The results for chromium as compared to the certified or compilation values were in excellent agreement.     

Determination of mercury by radiochemical displacement method

A radiochemical displacement method for the determination of micro amounts of Hg(II) has been developed. 65Zn was displaced from the Zn-1-(2-pyridylazo-2-naphthol) complex at pH 5 in borate buffers by Hg (II). 10-80 micrograms of mercury could be determined. Interference of various metal ions and methods for suppression have also been carried out.     

Determination of silicon in high purity metals by radiochemical NAA and CPAA

The indicator radionuclide³¹Si produced in neutron and deuteron activation analysis for silicon via the reactions³⁰Si(n,) and³⁰Si(d,p), respectively, is specifically separated from the irradiated sample by distillation as³¹SiF₄. In the case of aluminium, the distillation is carried out from a HF(HNO₃)H₂O₂ medium and in the case of molybdenum, niobium, tantalum, titanium and vanadium from a HF/HNO₃/HBr/H₂SO₄ medium. Using liquid scintillation counting, the achievable detection limits for neutron activation analysis are, depending on the type of the matrix, between 4–50 ng/g, and for the deuteron activation analysis of tantalum the detection limit is 5 ng/g.     

Simultaneous determination of mercury and selenium in biological materials by radiochemical neutron activation analysis

A simple and sensitive radiochemical neutron activation analysis (RNAA) method has been developed for the simultaneous determination of mercury and selenium in biological materials. The radiochemical procedure is based upon the digestion of irradiated samples with sulphuric and nitric acids followed by subsequent extractions of mercury and selenium into toluene, first of mercury from 7.5 M H₂SO₄-0.01M HBr media and after of selenium from 7M H₂SO₄-1 M HBr media. After washing of the organic phases with similar media, the mercury bromide was back-extracted into 0.034M EDTA in 5% aqueous ammonia and the selenium bromide into 0.14M H₂O₂ in aqueous solution. The¹⁹⁷Hg and the⁷⁵Se were counted on a Ge(Li) detector. The precision and accuracy of the method was checked by analysing NBS Standard Reference Materials: orchard leaves and bovine liver.     

Routine determination of mercury,arsenic and selenium by radiochemical Neutron Activation Analysis

A method for the determination of mercury, arsenic and selenium by neutron activation analysis is described. Radiochemical separations are performed by selective distillation followed by electrolysis of mercury on gold and precipitation of arsenic and/or selenium by reduction to the elemental form. The chemical yields are 80–90% for mercury and 90–100% for arsenic and selenium. Interference tests have been carried out with reference to those elements most likely to interfere with the analysis. Detection limits for mercury, arsenic and selenium using 0.1 g of sample are 0.2 ng g^–1, 2 ng g^–1 and 3 ng g^–1, resp. Detection limits can be improved using greater sample size and neutron flux density. Results from the analysis of several NBS standard reference materials are given.     

Determination of selenium in human diets by radiochemical neutron activation analysis.

A post-irradiation radiochemical separation technique was tested for the determination of selenium levels in diet samples, collected by using a duplicate portion technique, from both rural and urban population groups in Turkey. The technique involved sample irradiation, acid digestion, selective distillation, precipitation and filtration steps. During the separations it was possible to determine the yield of each sample using a stable selenium carrier. An average chemical yield of 71 +/- 3% was obtained for the radiochemical neutron activation analysis. For samples from urban and rural regions, the average selenium concentrations obtained were 0.14 +/- 0.04 and 0.07 +/- 0.02 mg kg-1, respectively. It was also possible to determine daily dietary selenium intakes, which were found to be 81 +/- 41 micrograms and 23 +/- 11 micrograms for the urban and rural groups, respectively. Although daily selenium intakes were found for a small number of subjects in this study, the separation technique developed can be used for determination of the selenium status in larger population groups.     

Neutron activation and radiochemical separation of selenium from environmental and food samples from and around Bombay using ethyl-α-isonitrosoacetoacetate

Neutron activation analysis has been applied for determination of selenium in environmental and food samples. Food and environmental samples from city, industrial and agricultural zones were collected with utmost care. Samples were activated in the flux 1·10¹³ n·cm^–2·s^–1 in the CIRUS reactor of BARC, Bombay, 75-Se was separated from 6.5N HCl solution using ethyl--isonitrosoacetoacetate (HEINA) reagent. The decontamination studies showed the method is very selective. Selenium contents of wheat, rice, vegetables, cereals pulses etc. and of soil, water, and deposits on plants and surface were determined by the procedure developed.     

Determination of trace elements in bottled water in Greece by instrumental and radiochemical neutron activation analyses

Summary Four different bottled water brands sold in Greece in the winter of 2001-2002 were analyzed for a wide range of chemical elements, using neutron activation analysis (NAA). The elements Na and Br were determined instrumentally (INAA), whereas the other metals and trace elements radiochemically (RNAA). The results indicated that the mean level of all the elements determined in the samples were well within the European Union (EU) directive on drinking water and accomplish the drinking water standards of the World Health Organisation (WHO) as well as of the Food and Drug Administration (FDA).     

Preliminary study of selenium and mercury distribution in some porcine tissues and their subcellular fractions by NAA and HG-AFS

Selenium and mercury distribution in porcine tissues and their subcellular fractions from a mercury-polluted area of Guizhou Province and from a not mercury-exposed area of Beijing in China have been studied with neutron activation analysis and hydride generation-atomic fluorescence spectrometry. Both the selenium and mercury levels are higher in Guizhou porcine tissues and their subcellular fractions than those in Beijing. These two elements are highly enriched in kidney and liver of Guizhou pig, while selenium is only enriched in the kidney of Beijing pig. Exposure of mercury may result in redistribution of Se and Hg in vivo. The Hg/Se molar ratio of the subcellular fractions is very low in the case of relatively low mercury level and gradually reaches to a high constant value with increasing level of mercury, which implies that selenium and mercury may form some special complexes in the organisms. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of cobalt,selenium and iodine by NAA in foodstuff by preconcentration of traces

Neutron activation analysis of cobalt, selenium and iodine requires pre-concentration of traces when the best possible conditions of sensitivity and accuracy are required at short irradiation times. The reason is ^60mCo, ^77mSe and ¹²⁸I present half-lives of 10.5 m, 17.5 s and 25 m, respectively, which do not allow neither to dissolve the sample nor to perform any radiochemical separation after irradiation. On the other hand, their emissions are located in the beginning of the spectrum (59, 161 and 441 keV, respectively) where the Compton continuum makes difficult the identification and measurement of the peaks. This paper describes how foodstuff samples are dissolved in pure HNO₃ by using conventional pressure pumps at 120–140 °C during 3–4 hours. Once cooled down the acid solution, distilled water is added and pH fixed at 1–1.5 with ammonia. 20 mg of APDC are added while stirring during 2 minutes and the solution is passed through 50 mg of activated carbon, where the Se traces are trapped. Then the filtered solution is adjusted to pH 4–6 with ammonia and passed through a fresh identical activated carbon filter where the iodine traces are caught. Finally, to the filtered solution is added 20 mg of cupferron at same pH, stirring for 2 minutes and passed through a third identical carbon filter, where the cobalt traces remain. In this way, we have the cobalt, selenium and iodine traces in three different, extremely pure carbon matrices, with a small, known mass of cobalt, selenium and iodine as background. Each filter is ready to be irradiated during a suitable time, to calculate separately at maximum sensitivity and accuracy the concentration of these three trace elements so important to human nutrition.     

Determination of cadmium using radiochemical neutron activation analysis

A method has been developed for the determination of cadmium in samples of food and biological materials using neutron activation analysis with radiochemical separation. The irradiated sample is digested in presence of cadmium carrier, with a nitric-perchloric mixture, evaporated to dryness, dissolved in 6M HCl and placed onto an ion exchange column loaded with Dowex 1-X8 resin in chloride form and conditioned with HCl 6M. The cadmium is retained in the resin. After a washing procedure with several portions of HCl of decreasing concentration, the cadmium is eluted with an ammonia-ammonium chloride buffer. The activity of ^115mIn which is in equilibrium with ¹¹⁵Cd, is measured using a NaI(Tl) well type detector. The method has been evaluated by analyzing certified reference materials with cadmium concentrations covering a range of 0.020 to 200 mg^.kg^-1. The agreement of the results with the certified values is within 95%, which gives an indication of the sensitivity and accuracy of the proposed method.     

Rapid measurement of selenium in biological samples using instrumental neutron activation analysis

A rapid instrumental system for measuring selenium via 17 second^77mSe has been applied to the analysis of a wide variety of biological specimens encountered in biomedical research. The reliability and versatility of the method is documented for serum and animal tissue specimens. Analysis results for SRM 1577 bovine liver show excellent accuracy and precision.     

Determination of protein content in some foodstaffs using 14 MeV NAA

The protein content of various corn-meals /rice, lupine, sorghum, pumpkin, linseed, water melon, tomato/ collected from Egypt and the USA have been determined by 14 MeV neutron activation analysis via¹⁴N/n, 2n/¹³N reaction. Non-conventional sources like tea and coffee residues were also investigated. The concentrations of trace elements determined by the X-ray fluorescence technique show definite differences even for a given type of seed produced in different geographical regions.     

Determination of Fe and Al contamination by NAA at preparation of traditional Mexican food

A study was carried out using NAA to measure the concentration of Al and Fe leached from kitchen ware into some popular Mexican sauces and juices. These elements were measured in red and green hot sauces cooked in Fe, Al and clay pans compared to a stainless steel pan. Similarly Al was measured in organe and grapefruit juices obtained using an Al extractor compared to a plastic one.     

Sequential substoichiometric radiochemical separation of selenium,thallium and cadmium

A procedure for sequential radiochemical separation of Se(IV), Tl(I) and Cd(II) has been developed. This procedure involves substoichiometric solvent extraction of these ions with 2-mercaptobenzothiazole (2-HMBT) under different experimental conditions.     

Rapid radiochemical separations using and induction furnace: Determination of sulphur in rocks

The use of an induction furnace for rapid radiochemical separations in neutron activation analysis of rocks is discussed in general and the activation analysis of sulphur in geological samples is described as a specific application. After irradiation the sample is heated in an induction furnace in a flow oxygen. The expelled sulphur oxides are adsorbed onto activated charcoal and measured in the well of a sodium iodide detector. The 3102 keV peak of the 5 minute³⁷S is used for analysis. The separation time is seven minutes, the yield 99% and the detection limit 200 μg S. Results of the analysis of ores are presented.     

Determination of arsenic,selenium and mercury in an estuarine sediment standard reference material using flow injection and atomic absorption spectrometry

A flow-injection analysis atomic absorption spectrometric (FIA-AAS) method was developed for the determination of trace amounts of arsenic, selenium and mercury in a proposed estuarine sediment standard reference material (SRM 1646a). The samples were prepared in two manners: a) A wet digestion procedure with HNO₃, H₂SO₄, and HClO₄ using a reflux column and b) A microwave-oven digestion procedure utilizing HNO₃, H₂SO₄, and HCl for As and Se, and HNO₃ for Hg. Microwave-oven digestion provides results comparable to those found by reflux column digestion and reduces the sample preparation time by a factor of 10. The proposed method employing the microwave-oven digestion procedure coupled with FIA-AAS for As and Se, and FIA-CVAAS for Hg, has detection limits of 0.15 ng As/ml, O.17 ng Se/ml and 0.15 ng Hg/ml.On leave from the Defense Metallurgical Research Laboratory, Hyderabad, India