T04_P21

A home-made semiautomatic graphitization device for AMS ¹⁴C dating at NTUAMS Lab

Shen T¹, Chang H¹, Li H¹

¹Department of Geosciences, National Taiwan University, Taipei, Taiwan

We have built up a semiautomatic graphitization system with 6 units. The system can be connected with EA and IRMS or run alone with gas inlet. Once the CO₂ is transferred into the reactor and measured its pressure, pure H₂ is added into the reactor with 2.2 times of PCO₂. The CO₂ will be reduced to graphite at 550°C. This 6-unit reaction system costs < US$30K. Up to date, four background CO₂ gas input samples show that the ¹⁴C/¹²C values of the graphite samples made by the reaction system range from 1.56∙10^-15 to 3.06E^-15, indicating very low background of the system. In the first batch test, six coal background (BKG) samples through the EA to the graphitization reactors yielded the ¹⁴C/¹²C values of the produced graphite samples ranging from 6.9E-15 to 4.13∙10^-14. The higher ¹⁴C/¹²C values are mainly attributed to weak ¹²C current due to poor quality of the graphite. The second batch test contained 3 OXII, 2 BKG and 3 FIRI-M (4th inter-comparison sample with consensus age of 11139 yr BP). The measured ¹⁴C ages of the three FIRI-M are 11514±142 (¹²C current = 5.7 μA), 11653±307 (0.53 μA) and 11968±835 yr BP (0.076 μA), respectively. The age uncertainty increases with weakness of the graphite target strength. Nevertheless, the system is under refining with more tests. With the low cost, the system is able to provide convenient and effective graphitization for organic samples.