Small-mass AMS radiocarbon analysis at ANTARES

Recent developments to further improve the graphitisation reaction rate and efficiency for small samples are presented. We have investigated three different methods of activating the Fe catalyst: (1) 750 mb H-2 at 600 degreesC for 1 h, (2) 750 mb H-2 at 600 degreesC for 24 h, and (3) 500 mb O-2 at 450 degreesC for 0.5 h followed by 750 mb H-2 at 600 degreesC for 1 h. The results show that method 3 is the most suitable method for activating the Fe catalyst for the graphitisation of small-mass samples as it helps to improve both the reaction rate and efficiency. In addition, a simple approach is presented to determine the C-14 content and mass of extraneous carbon that is incorporated during sample preparation. These data were then used to correct for two test series of reference materials (FIRI-H and IAEA-C7) containing less than 200 mug of carbon, using three different formulations of procedural background correction. The corrected values of test samples are mostly in agreement with their consensus values. This indicates a good accuracy of our C-14 analysis of small-mass samples. (C) 2004 Elsevier B.V. All rights reserved.