CO2-laser decomposition method of carbonate for AMS 14C measurements

A CO2 laser decomposition method enabled the efficient preparation of carbonate samples for AMS 14C measurement. Samples were loaded in a vacuum chamber and thermally decomposed using laser emission. CO2 liberated from the carbonate was directly trapped in the cold finger trap of a small CO2 reduction reactor and graphitized by a hydrogen gas reduction method using catalytic iron powder. The fraction modern values for 0.07–0.57 mg of carbon, obtained from 200 μm-diameter spots of IAEA-C1, varied with sample size in the range of 0.00072 ± 0.00003 to 0.00615 ± 0.00052. The contamination induced by the laser decomposition method and the following graphite handling was estimated to be 0.53 ± 0.21 μg of modern carbon, assuming a constant amount of extraneous carbon contamination. This method could also make it possible to avoid the time-consuming procedures of the conventional acid dissolution method that involves multiple complex steps for the preparation of carbonate samples.