Plasma source mass spectrometry offers very exciting potential for ultra low level trace elemental analyses of biologically and environmentally important samples. Only within the last year has commercial instrumentation been introduced which will allow meaningful implementation of this technique. It has been well known for some time that the inductively coupled plasma and other plasma types are excellent ion sources. By coupling such an ion source to the vacuum system of a mass spectrometer, sub-ppb detection levels are readily obtained. The more conventional optical emission detection gives detection levels roughly 100 times higher. In many biological and environmental samples, there is high interest plus a compelling need to realistically analyze materials at the low ppb levels. This proposal addresses several important areas in which low ppb detection levels are of critical importance. These areas are (1) a continuing investigation of technetium-99m as applied to the practice of nuclear medicine. To make this technique more effective, the inorganic chemistry of technetium needs to be carefully determined. In many instances this will involve the need for analytical determinations at levels presently unobtainable without preconcentration techniques which introduce an element of suspicion since sample contamination may result. In another area, gold-based arthritis drugs will be studied for their particular metabolites. This is a situation where atomic spectroscopy is imperative yet the levels of detection are simply not low enough to proceed as well with this project as is necessary without preconcentration. Plasma source mass spectrometry will readily allow speciation by HPLC and low ppb detection levels. In the environmental area, ultra trace metals in biological matrices are extremely important in a variety of toxicity studies. Here not only the low detection level advantage is necessary but the need of multielement determination available from the plasma source. Also of environmental concern are the multitude of halogenated organic compounds released into the atmosphere and the concern over their possible effects. With GC-plasma source mass spectrometry, it should be possible to reach sub-pg/sec detection levels yet allowing the high specificity of atomic spectrometry. Also there is an advantage of doing multielement chromatography to remove or reduce chomatographic ambiguities.