Isotope tracer studies, particularly 14C measurements, play a key role in biological, nutritional, and pharmaceutical research. AMS is the most sensitive isotopic method and provides the lowest detection limits currently available. Despite these advantages, AMS has not yet become a routine laboratory method. Part of the reason why AMS is rarely used is its high cost, but its cost would decrease if AMS were used more widely. A major reason why AMS use is rare is that sample preparation for AMS is slow, difficult, and labor intensive. Sample preparation accounts for more than 50% of the total analytical cost of 14C-AMS. At present, biological samples must be reduced to solid graphite before they can be analyzed by AMS. Converting biological samples to graphite involves two major processes: oxidation (combustion of organic compounds to CO2) and reduction (converting CO2 into graphite). Dried organic samples are transferred into pre-sterilized quartz tubes, a small amount of copper oxide is added, and the tubes are heat-sealed. The samples are then combusted at 900 oC for 2 h. The resulting CO2 is cryogenically transferred into septa sealed reaction tubes containing iron and zinc catalysts. The reaction tubes are then baked at 530 oC for 6-7 h to form graphite. The graphite produced is pounded into aluminum target holders and used for AMS measurements. We describe a detailed sample preparation protocol for graphitizing biological samples for AMS, and review studies that have used this procedure in biological studies.
See more of Poster Session II
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)