Concentrations of up to 16 elements have been determined in subcellular fractions of bovine kidney using INAA methods. Levels of Rb and Se have been measured by a cyclic INAA method. A conventional INAA method consisting of 2 irradiations and 3 counting periods has been employed to determine the other elements. Accuracy of measurements has been evaluated by analyzing several standard reference materials. Trace element content of reagents used has been investigated in detail. Fresh samples of bovine kidney have been homogenized in a buffer containing sucrose and HEPES, and the homogeneate separated into nuclei, mitochondrial, lysosomal, microsomal and cytosol fractions by successive differential centrifugation. Concentrations of trace elements have been measured in these fractions using the INAA methods.
Several bioanalytical techniques have been employed in conjunction with instrumental neutron activation analysis (INAA) to study metalloproteins and protein-bound trace elements in bovine kidneys. The accuracy of the INAA method developed has been evaluated by analyzing certified reference materials. Up to 29 elements can be reliably determined in biological tissue samples by INAA. Dialysis of the bovine kidney homogenate shows that more than 90% of Ca, Cd, Cu, Fe, Mg, Mn, Mo, Se, V and Zn, and about 20% of Br are bound to macromolecules, mainly proteins. A combination of gel filtration and ion exchange chromatography, chromatofocusing, electrofocusing, ammonium sulphate precipitation and INAA of the bovine kidney microsomecytosol subcellular fraction further indicates that much of the copper is associated with a single protein of an isoelectric point around 5 and a molecular weight of about 30 000 daltons. Some results on manganese proteins are also reported.
Authors:R. Rao, L. McDowell, C. Jayawickreme and A. Chatt
The homogeneity of four reference materials was evaluated for Se by cyclic instrumental neutron activation analysis (CINAA). The relative standard deviation for Se measurements at ppb levels by CINAA was <12% for NIST Wheat Flour (SRM 1567) in 5–10 mg samples, while it was <11% for Chinese Hair (HH–CH-1), <13% for IAEA Animal Muscle (H-4) and 25% for IAEA Animal Blood (A-13) in 50 mg samples. The highest relative subsampling uncertainties were observed in the mass range of samples 50 mg for Chinese Hair, 100 mg for Wheat Flour and Animal Muscle and 300 mg for Animal Blood. The results of a one-way analysis of variance indicate that all reference materials above these mass ranges are adequately homogeneous with respect to Se distribution. Our data suggest that these materials, except Animal Blood, can be used as reference standards for Se in Quality assurance programs well below the sample masses re commended by the issuing agencies.
Authors:A. Chatt, H. Dang, B. Fong, C. Jayawickreme, L. McDowell and D. Pegg
Neutron activation analysis (NAA) methods have been developed for the determination of major, minor and trace elements in duplicate diets and individual food items. These include a cyclic instrumental NAA (CINAA) method for measuring Se content through its short-lived nuclide77mSe; epithermal INAA (EINAA) for I and As; conventional INAA for Br, Ca, Cl, Co, Cr, Fe, K, Mg, Mn, Na, Rb, Sb, Sc, Sn and Zn; combination of EINAA and INAA for Al; radiochemical NAA (RNAA) for As, Au, Co, Cu, Fe, Hg, Mo, Sb, Se and Zn; and preconcentration NAA (PNAA) for U and Th. Accuracy of measurements have been evaluated by analyzing a number of biological and diet reference materials. Multielement concentrations of diets and foods have been measured by these methods.