AMS 14C measurements of organic samples require combustion to obtain CO2 for graphitisation and for δ13C determination by stable isotope mass spectrometry. A simplifying step is therefore to combine the combustion in stable isotope analysis with cryogenic trapping of CO2 for AMS graphite targets. Automated or semi-automated trapping devices for CO2 coupled to elemental analysis continuous flow isotope mass spectrometers has previously been published [1] [2]. We present here a simple CO2 trapping device based on a modified Gilson 220XL robot coupled to the inlet manifold system of GV Instruments IsoPrime. A small dewar automatically held at a constant level of liquid nitrogen is added to the existing Gilson robot arm. The CO2 samples for graphitization are trapped in small septum sealed vials. The Gilson is operated with a dual needle to ensure a constant helium flow at all times and to let the sample CO2 into the trapping vials. The system is capable of batch combustion and analysis of 25 samples. It is under full computer control by the mass spectrometer software. All trapping parameters such as flush time prior to trapping and total trap time are adjustable through the standard user interface.
References 1. Bronk Ramsey, C. and M.J. Humm, On-line combustion of samples for AMS and ion source developments at ORAU. Nuclear Instruments and Methods in Physics Research B, 2000. 172: p. 242-246. 2. Aerts-Bijma, A.T., J. van der Plicht, and H.A.J. Meijer, Automatic AMS sample combustion and CO2 collection. Radiocarbon, 2001. 43: p. 293-298.
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See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)