A REVIEW OF THE CAPABILITIES OF ICP-MS FOR TRACE-ELEMENT ANALYSIS IN BODY-FLUIDS AND TISSUES

ICP-MS is a powerful analytical technique for the determination of tra ce and ultra-trace elements in biological materials. Results are given of the analysis of human serum and of several biological reference ma terials (bovine liver, milk powder, wheat flour and pig kidney). Becau se concentrations of many trace metals of interest in these materials are low, dilution should be kept as limited as possible, although conc entrations of certain concomitant elements (e.g. Na, K) can be high en ough to cause significant suppression or enhancement of the ion signal . The result is that the dissolution procedure becomes a critical step in the analysis. Microwave digestion, wet digestion with several acid s (HNO3, HClO4, HF) and simple dilution are compared with each other. In addition, three possible approaches to overcome these problems are discussed, namely the internal standardization method, the standard ad dition method and the isotope dilution method. Furthermore, ICP-MS is also more susceptible than initially expected to isobaric interference s arising from the plasma, the acids used in the sample preparation or the sample itself. These interferences are generally less important a bove a mass number of 80. Nevertheless, several researchers have inves tigated the possibility of removing the trace metals from the matrix o r of using correction formulae based on the isotopic abundances of the elements. Some of these are evaluated. The need for identifying and q uantifying chemical species, not just the elements, is well recognized . One of the reasons why elemental determination may not suffice is th at different species of the same element may have a different chemical and toxicological behaviour. Arsenic (As(III), As(V)) and mercury (or ganomercury) are typical examples. Since ICP-MS offers very low detect ion limits, it may be applied as a continuous metal-specific detector after a chromatographic separation of the species. Applications on thi s subject are discussed.