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  • Author or Editor: G. Iyengar x
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Abstract  

A simple radiochemical machine incorporating ion-exchange procedures has been described. The system has been tested repeatedly for the determination of Cd, Co, Cr, Cu, Mn and Mo at ultra trace concentration levels in a variety of biological samples such as reference materials, human blood serum, human milk, hair and certain dietary materials, thereby demonstrating its suitability for practical use. The procedure can also yield results for A, Au and W, without any further chemical manipulations. Results show <1, 0.12, 0.18, 983, 0.61 and 0.91 g/l for Cd, Co, Cr, Cu, Mn and Mo, respectively, in human blood serum. Corresponding concentrations in human milk are <1, 0.25, <1, 186 to 310, 4 to 40 and 5.8 g/l. Among the reference materials, IAEA milk standard A-11 shows 1.85, 5.1, 17, 380, 260 and 101 ng/g for Cd, Co, Cr, Cu, Mn and Mo, respectively. Corresponding concentrations in animal muscle H-4 are 4.1, 5, 10.2, 4000, 455 and 45 ng/g. Importantly, this scheme has been applied to process large number of samples from single investigations such as those arising from dietary studies, obtaining quick and reliable data for routine use.

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Abstract  

The complexities involved in dealing with the requirements of trace element research studies in the life sciences demand comprehensive planning of the investigations and use of a variety of techniques. It also requires a combination of biological insight and analytical awareness on the part of the investigators in order to obtain valid samples for analysis. Thus, the generation of meaningful conclusions from elemental composition studies on biological systems is a strictly multidisciplinary task, an approach that is vital for the overall success of the investigations. In addition, new initiatives are needed to produce multipurpose biological reference materials to cope with the growing demands of this multifaceted area of research. These aspects are discussed.

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Abstract  

Loss of sample weight due to matrix decomposition of erythrocytes, whole blood and blood plasma during long time reactor irradiation was investigated. During a weighing sequence extending over an interval of 5 days with respect to the time of opening of the sample contained in sealed quartz tubes, a loss of sample material up to 11% was observed. Use of post-irradiation weight of partly recovered sample material introduces positively biased systematic error to the results. It is necessary to use preirradiation weight with 100% post irradiation sample recovery in order to eliminate this type of errors.

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Abstract  

NAA was used to analyse K, P, Cl, Na, Fe, Zn, Rb, Mn, Se, Co and Ag in bovine liver, before and after homogenisation, using brittle fracture technique (BFT). The liver specimen analysed in this experiment did not present any extreme variation problem with respect to the trace element distribution profile in the liver matrix. Elaborate sample-handling and the possible influence of the interfering components such as residual blood, blood vessels and fat on the concentration profile of the above mentioned elements is discussed. In another experiment using60Co,134Cs,141Ce and198Au radiotracers, the physical distribution of the added tracers following the process of biological matrix disintegration, for homogenisation purposes was studied at the 1 mg to 10 pg concentration levels. The results indicate that BFT is an efficient, clean and practical tool that meets the homogenisation problems because of its suitability to practically all types of biomedical samples.

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Abstract  

In order to reduce analytical expenses by the re-use of typical ion-exchange resins and partition chromatographic column supports, frequently used in large scale routine analysis of biological samples in many radiochemical laboratories, the problem of their recovery was studied in column and batch operations. The difficulties encountered with respect to some elements are discussed in details.

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Abstract  

Using rat liver as an example, the implications of postmortal changes such as cell swelling, imbibition and autolysis on the elemental composition of body organs were studied. Of the three elements investigated in this part of the experiment, concentration of Co increased from about +50 per cent to +120 per cent of control in all groups retained at room temperature and the content of Co rose by about 95 per cent; Cs increased less extensively than Co in all groups at room temperature; Se values showed up to 50 per cent increase in concentration only and there was no change in content. The changes were less marked for all the three elements at −15°C.

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Abstract  

A method for boron determination based on 11B(p, a)8Be reaction is described. The irradiations were performed with 800 keV protons and the alphas were counted with 2 PIPS detectors at an angle of 150° to the beam direction. The method is simple and permits the determination of boron at g/g level in biological materials and sub-g/g level in metals, alloys etc.

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Abstract  

Samples of diets from China, Japan, Korea, India, Pakistan and Philippines were analyzed using epithermal and radiochemical neutron activation analysis (ENAA and RNAA, respectively) within the framework of the IAEA project “Reference Asian Man”. The RNAA procedure was based on alkaline-oxidative fusion followed by extraction of elemental iodine in chloroform. The analytical methods employed are discussed in terms of detection limits and uncertainties of the results obtained. For quality control purposes a number of NIST biological reference materials, namely diets and foods were analyzed. Results for the diet samples indicate that achieving the WHO recommended daily allowance for iodine may be a problem in most of the above given countries.

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Summary  

The International Atomic Energy Agency (IAEA) has, for many years, supported research on human dietary intakes of trace elements taking advantage, for analysis, of the possibilities offered by nuclear techniques, particularly neutron activation analysis (NAA). This paper summarizes the results obtained from studies in more than 20 countries in which special emphasis was placed on the application of reliable methodologies (written protocols, special equipment, analytical quality control, etc.). Considerable variation was observed among dietary intakes of essential minor and trace elements though most elements showed a pattern of adequate nutrition in most countries. However, for some elements such as calcium, iodine, iron and zinc, the intakes in many countries were lower than the dietary requirements.

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Abstract  

Analytical quality assurance procedures adopted for use in the IAEA Co-ordinated Research Project on Ingestion and Organ Content of Trace Elements of Importance in Radiological Protection are designed to ensure comparability of the analytical results for Cs, I, Sr, Th, U and other elements in human tissues and diets collected and analysed in nine participating countries. The main analytical techniques are NAA and ICP-MS. For sample preparation, all participants are using identical food blenders which have been centrally supplied after testing for contamination. For quality control of the analyses, six NIST SRMs covering a range of matrices with certified and reference values for the elements of interest have been distributed. A new Japanese reference diet material has also been developed. These quality assurance procedures are summarized here and new data are presented for Cs, I, Sr, Th and U in the NIST SRMs.

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