TRACE-ELEMENTS IN MEDICINE - SPECIATION - THE NEW FRONTIER

Speciation of trace elements in body fluids and tissues consists of defining the many biocomponents to which the trace elements are bound and to explain their mobility, storage, retention and toxicity. Such new frontiers are now open for interdisciplinary research. It is necessary to maintain the integrity of the metal-ligand binding and to check the mass balance of the protein and the trace element throughout the isolation steps. A distinction is made between chemical speciation of the trace element and speciation as a part of cytology. Some methods are discussed for the speciation of As and Cr in serum, together with the limitations of the speciation procedure. It is assumed that the biomolecule and the trace element which are subsequently detected in the same fraction, are indeed associated with one another. This is not necessarily the case, so that confirmation with different means of identification of the biocomponent is imperative. A major problem in speciation work is due to the fact that immense hazards exist for contamination and losses of the trace element. In cytology, meaningful speciation cannot be achieved by ultracentrifugation of the different cell organelles. The best approach nowadays is to use microbeam techniques which are able to locate the trace element in situ, and even to attribute a semiquantitative value to its presence.