Advances in instrumental methods for the measurement and speciation of trace metals

Progress in understanding the role of trace metals in biology has been largely dependent on the development of sensitive, accurate and precise analytical methods. Atomic spectroscopic techniques, particularly atomic absorption, have made the greatest contribution. Key to the success of such analytical techniques has been the simplification of sample processing so that contamination is minimized. Electrothermal atomization has allowed sensitivity limits to be lowered sufficiently so that even ultra-trace metals can be detected. More recently, mass spectrometric detection of metal ions has added to the repertoire of available instrumentation, particularly with the use of inductively coupled plasma to introduce ions into the mass analyzer. These analyzers are suitable for multielement analysis. More conventional mass spectrometric analysis of metal chelates offer an alternate solution but require considerable specimen preparation time. Intracellular localization of trace metals necessitates complex specimen processing prior to analysis on instruments that are highly sophisticated and expensive. Metal speciation is a rapidly growing area of trace metal research, with the major advances coming from coupling of the separation process, such as capillary electrophoresis or high performance liquid chromatography, with the analytical instrument for metal detection. Inductively coupled plasma-mass spectrometry has proved to be an excellent choice for such detection purposes. Refinement of these methods as well as more widely available instruments for microanalysis will add greatly to continued advances in our knowledge of the role of trace metals in biology and medicine.