Gas chromatograph-combustion system for 14C-accelerator mass spectrometry

A gas chromatograph-combustion (GC-C) system is described for the introduction of samples as CO2 gas into a 14C accelerator mass spectrometry (AMS) system with a microwave-plasma gas ion source. Samples are injected into a gas chromatograph fitted with a megabore capillary column that uses H2 as the carrier gas. The gas stream from the outlet of the column is mixed with O2 and Ar gas and passed through a combustion furnace where the H2 carrier gas and separated components are quantitatively oxidized to CO2 and H2O. Water vapor is removed using a heated nafion dryer. The Ar carries the CO2 to the ion source. The system is able to separate and oxidize up to 10 μg of compound and transfer the products from 7.6 mL/min of H2 carrier gas into 0.2−1.0 mL/min of Ar carrier gas. Chromatographic performance and isotopic fidelity satisfy the requirements of the 14C-AMS system for natural abundance measurements. The system is a significant technical advance for GC-AMS and may be capable of providing an increase in sensitivity for other analytical systems such as an isotope-ratio-monitoring GC/MS