This research project is aimed at developing an innovative technique to detect carbon-14 and tritium in biological samples at concentrations below background. The instrument is based on the utilization of a hot, dense electron-cyclotron-resonance (ECR) plasma for ion production. Mass interference is eliminated by conversion of ion charge states. Since no accelerator is needed, the device is compact, about the size of typical analytical mass spectrometers widely employed in biomedical laboratories, and it is much less expensive in both initial costs and operating costs than accelerator mass spectrometry (AMS). The proposed technique has the potential to measure carbon-14 and tritium with attomole sensitivity. Furthermore, the technique is well suited to biological research because tissue samples can be vaporized and analyzed directly in the gaseous form. Other features include higher throughput than AMS, greater reliability and shorter downtimes, and applicability to tracer elements such as Clorine-36 and I-129 that have a high electron affinity (sensitivity should be much higher for these elements than measurements using radioactive counting methods). The proposed new analytical instrument has great potential to be widely used by biomedical researchers in radioactive tracing to study the fate of carcinogens, mutagen and toxins at the molecular level. PROPOSED COMMERCIAL APPLICATION The proposed instrument is very sensitive, compact (with the size of typical analytical instruments with mass spectrometers), cost effective and reliable with high sample throughput. Thus, it will be widely used by researchers in major biomedical centers for cancer research. Pharmaceutical companies will benefit from the technique in health risk assessment. Applications by large hospitals in clinic to screen cancers is also expected.