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In the determination of trace elements in biological materials, speciation is of particular importance as the essential effects or toxicity of an element and its metabolic behaviour depend to a large extent on the chemical forms in which it is present in the organism. Speciation is relatively easy if a property of a particular compound can be measured directly in the sample without interference from the other components of the material, e.g., the enzymic activities of the metallo-enzymes. Another possibility for speciation is immunoassay, which likewise allows direct determination of a particular trace element. At present, however, with most trace elements both fractionation methods and analytical procedures have to be combined and speciation has to be carried out by determining the elemental content in the separated fractions. The methods and apparatus used in taking, storing and preparing the samples can, therefore, not be selected solely according to the requirements of trace element determination, but it is also essential to ensure that the biological structures of the components to be separated remain intact. In this work the need for speciation in the investigation of the toxic and essential effects of trace elements is shown with the help of some examples, and the problems that can occur in the various steps of sampling, storage and sample preparation are discussed.

Bone samples from the iliac crest were taken from 20 subjects and the content of some trace elements (iron, zinc, selenium, cobalt, strontium, aluminium, scandium, rubidium and fluorine) and of the matrix elements calcium, phosphorus and sodium was determined. The samples were taken in accordance with Burkhardt's method, which is often used in hospital for bone biopsies. The sources of errors occurring during the analysis of trace elements using this clinical procedure and the contamination of the samples by blood and the surrounding tissue are discussed. In-vivo activation analysis is also discussed as an alternative method of element analysis of the skeleton.

The concentrations of arsenic, chromium, cobalt, iron, manganese, rubidium, selenium and zinc were determined by instrumental neutron activation analysis (INAA) in the homogenate and the subcellular fractions of lungs from rats fed either a selenium-adequate or a selenium-deficient diet. Feeding of the selenium-deficient diet led to a considerable decrease in the selenium levels in all samples investigated but had no significant effect on the concentrations of the other elements. All elements were distributed inhomogeneously among the subcellular fractions. Selenium, iron and zinc had their highest concentrations in the microsomal fraction, chromium and cobalt in the nuclear fraction and arsenic and rubidium in the cytosol. Information about the trace element-containing proteins in the lung cytosol was obtained by size exclusion chromatography and online multi-element analysis of the separated protein fractions by mass spectrometry in conjunction with an inductively coupled plasma (ICP-MS). The results suggested that arsenic, cadmium, cobalt, copper, iron, manganese, molybdenum, nickel, selenium and zinc are present in the rat lung cytosol in several protein-bound forms. [ABSTRACT FROM AUTHOR]