Involvement of analytical chemistry in chemical speciation of metals in clinical samples

The different chemical species of the trace elements in a living system are determinants for their physiological behaviour. Their study is necessary to improve the understanding of trace element kinetics and metabolism. In a complex matrix, such as biological fluids and tissues, some trace elements will occur as free or mononuclear ions; other as low molecular weight complexes, as reversible or irreversible macromolecular complexes. Speciation investigations entail the separation of the compounds, followed by the measurement of the trace element in the different fractions. Frame-work-procedures are outlined and attention is drawn on the many difficulties that can be encountered. These include the complexity of the matrix, insufficient specificity of the separation of biocompounds, fortuitous contaminations with trace elements, and cutting the original metal-protein binding. State of the art description is given for the speciation studies of AI, As, Cd, Cr, Co, Cu, Hg, Ni, Pb, Pt, Se, Sn, and Zn.