Comparison of I 13C and 14C activities of CO2 samples combusted in closed-tube and elemental-analyzer systems

For combustion of organic samples, a closed tube-combustion (CTC) method is generally used, but this method requires much time and labor. The AMS facility at the Center for Chronological Research, Nagoya University, has established a CO2 production and purification system using an elemental analyzer (EA) connected to cryogenic traps. This system enables faster combustion and CO2 purification of samples than does the conventional CTC method. We compared measured carbon yields, I 13C values and 14C activities between EA and CTC samples of carbon standards of various sample quantities. This newly developed EA system had low background 14C activity due to sample preparation; the background activity was similar to that observed for the CTC method. The EA system also showed high precision and accuracy for I 13C and 14C measurements. The EA sample data obtained from conventional quantities (>1mg carbon) of standards showed good agreement with the results obtained by the CTC method and with the consensus values, though background contamination was detected for samples containing