RAPID PRODUCTION OF GRAPHITE WITHOUT CONTAMINATION FOR BIOMEDICAL AMS

The application of AMS to the detection of C-14 makes possible a new class of sensitive experiments in molecular biology. Such experiments inherently produce large numbers of samples for the determination of biological variability in molecular interactions. The samples vary in C-14 concentration over many orders of magnitude. We added TiH2 to aid the reduction of CO2 by zinc in a sealed tube to reproducibly make graphite without sample cross-contamination. The CO2 is transferred from a combustion tube to the reaction tube through a disposable plastic manifold. The sealed tubes are heated to a single-reaction temperature in a muffle furnace. The process is complete within 5 h. Bulk isotopic fractionation in the finished graphite is less than 0.5%.