Metrological assessment of the high-accuracy RNAA method for determination of cobalt in biological materials.

The paper summarizes work on the development of the high-accuracy RNAA method for the determination of trace amounts of cobalt in biological materials. The method is based on a combination of neutron activation with selective and quantitative isolation of the analyte in a state of high radiochemical purity by use of column chromatography followed by gamma-ray spectrometric measurements. The method was devised according to a set of rules, which were formulated to obtain high accuracy of the method. The procedure has been also equipped with several criteria as key factors in quality assurance. Qualification of the high-accuracy RNAA method as a primary ratio method has been demonstrated and its usefulness in the certification of the candidate reference materials tea leaves and mixed Polish herbs is presented.

Preparation and use of reference materials for quality assurance in inorganic trace analysis.

A general preparation and certification scheme used in the Institute of Nuclear Chemistry and Technology (INCT) for the preparation and use of certified reference materials (CRMs) for inorganic trace analysis is presented and contrasted with approaches used by other CRM producers. 'Definitive' and 'very accurate' methods have a role, based on a combination of neutron activation and quantitative and selective post-irradiation isolation of an indicator radionuclide by column chromatography. Natural matrix CRMs of biological origin including the typical food products are reviewed and the need is identified for new well-characterized materials that would also be suitable for micro-analytical techniques such as PIXE, EDXRF, SS-AAS, etc. There are various approaches to studying homogeneity and its relationship with particle size distribution of a material, and the many problems associated with reliable particle size measurements of CRMs by various techniques are illustrated using real examples. There is an equation relating Ingamells' sampling constant to the mass of single particle of a powder material and this theoretical approach has been compared with experimental results obtained for some CRMs.

Some difficult problems still existing in the preparation and certification of CRMs.

Differences between particle size measurements of CRMs by various methods are discussed and the importance of the reliability of such data for proper estimation of the homogeneity of the material is emphasized. On the basis of a very simple model, the dependence of the Ingamells' sampling constant on the average mass of a single particle of the material is derived, and theoretical predictions are compared with the experimental results. Various approaches to the certification of the candidate RMs are briefly reviewed. The merits of the approach being used in this laboratory to evaluate data obtained in the interlaboratory comparison, and to assign certified and information values, is discussed. The conclusions are supported by results obtained for selected trace elements by use of "definitive" (primary) and "very accurate" methods. Some observations on the unusual resistance of some biological materials to wet ashing and the resulting possibility of making analytical errors are mentioned.

Accurate determination of cobalt traces in several biological reference materials.

A newly devised, very accurate ("definitive") method for the determination of trace amounts of cobalt in biological materials was validated by the analysis of several certified reference materials. The method is based on a combination of neutron activation and selective and quantitative postirradiation isolation of radiocobalt from practically all other radionuclides by ion-exchange and extraction chromatography followed by gamma-ray spectrometric measurement. The significance of criteria that should be fulfilled in order to accept a given result as obtained by the "definitive method" is emphasized. In view of the demonstrated very good accuracy of the method, it is suggested that our values for cobalt content in those reference materials in which it was originally not certified (SRM 1570 spinach, SRM 1571 orchard leaves, SRM 1577 bovine liver, and Czechoslovak bovine liver 12-02-01) might be used as provisional certified values.

A comprehensive study on the contents and leaching of trace elements from fly-ash originating from Polish hard coal by NAA and AAS methods.

In order to assess the environmental risks associated with the emission of fly-ash into the atmosphere and its storage on waste heaps, the trace element contents of fly-ashes from burning Polish hard coal were determined by a newly developed INAA method. Leaching of trace elements from the fly-ash by water and H2SO4 solution (pH approximately 2.5) simulating acid rain, respectively, was studied using AAS and spectrophotometric methods. Analogous experiments were done with neutron-irradiated fly-ash, following the composition of the eluate gamma-spectrometrically. The new fine fly-ash (CTA-FFA-1) candidate reference material was prepared, and the certification was undertaken on the basis of an international intercomparison run. Preliminary evaluation of results shows that at least 38 elements will be certified and, in addition, the "information values" for at least 12 elements will be given.

Hair zinc and copper concentration in survivors of myocardial infarction.

Increased Zn/Cu ratio in the diet, and consequently in the body, was suggested to be of importance in the pathogenesis of atherosclerosis. Head hair of 29 male survivors of myocardial infarction and of 23 control males was studied for the concentration of Zn and Cu. The Zn hair concentration and Zn/Cu ratio in survivors of myocardial infarction was significantly higher in comparison with controls. The inclusion of the Zn/Cu ratio into the discriminant analysis using total cholesterol and HDL cholesterol considerably improved the coefficient R2 and decreased the number of cases not properly classified.