TRACE-ELEMENT ANALYTICAL SPECIATION IN BIOLOGICAL-SYSTEMS - IMPORTANCE, CHALLENGES AND TRENDS

Speciation of trace elements is a relatively new field and it was in t oxicology that the relationship between the chemical form of a metal a nd its harmful effects was first recognized. The present need for chem ical speciation information in biochemistry bioinorganic and clinical chemistry is documented in an attempt to justify the present demand fo r innovative chemical speciation strategies and analytical technologie s. The challenge and complexity of speciation is stressed and three di fferent categories of analytical speciation of increasing analytical d ifficulty are proposed. Analytical strategies developed so far to try to tackle speciation problems (computational approaches, direct specie s-specific and hybrid techniques) are reviewed and critically assessed for biological materials. It is indisputable these days that in most cases of real-life analytical speciation we have to resort to the deve lopment and use of hybrid techniques combining an adequate separation technique for the species physical separation and an element specific detector such as those based in atomic spectrometry. Examples of such strategies, as developed mainly in the author's laboratory and includi ng chromatographic and non-chromatographic type hybrid strategies coup led to flame, plasma and electrothermal vaporization atomic detectors, are discussed in more detail. Finally, in light of the latest trends observed in this new held, the author attempts to cast a forward look into the foreseeable future of analytical speciation research in biolo gical and biomedical sciences. The urgent plea for quality assurance i n nonroutine analysis and the concept of using complementary analytica l techniques and definitive methods to attack the complexity of chemic al speciation in biological systems are particularly highlighted. (C) 1998 Elsevier Science B.V.