Beyond total element analysis of biological systems with atomic spectrometric techniques.

One of the fundamental limitations of atomic methods in biological analysis is their inability to distinguish individual physico-chemical forms of the metal. After a brief overview of 'hot' trace elements and atomic techniques used for total element analysis in bioanalytical work, the importance and main challenges of speciation of toxic metals in biological systems is addressed. The main analytical problems of speciation and present techniques/analytical strategies to tackle this problem are highlighted. Recent work on metal speciation in our laboratory is described in order to show that analytical difficulty is dependent on the chemical nature of the sought species (i.e., moving from 'stable/kinetically inert' to 'unstable/fast reacting' species determinations). New analytical strategies for more stable species (e.g., methylmercury) by coupling a powerful separation technique with specific (atomic) detectors are described. The concept and analytical application of non-chromatographic and vesicles-mediated HPLC-volatile species generation-atomic detection to the speciation of toxic species of Hg, As or Sn is discussed. It is emphasized that the complexity of toxic metal speciation in biological matrices calls for a 'several-complementary' analytical strategies approach. This concept of applying different-principle-based separation units (e.g., ultramicrofiltration, FI or HPLC columns with different adequate packings) coupled with complementary detectors (usually atomic ones) for tackling complex problems is stressed. Comparative studies on the speciation of aluminium and silicon in human serum carried out in the author's laboratory are used throughout to illustrate this important point. Finally, some clinically relevant conclusions derived from such trace metal speciation research are highlighted.