An automated processing line for the extraction of dissolved inorganic carbon from water for radiocarbon analysis

At ANSTO, we have developed an automated dissolved inorganic carbon (DIC) processing line, known as A-DIC, designed to sequentially process 10 water samples for radiocarbon analysis without any operator intervention. The A-DIC works at ambient pressure using helium (He) gas as a carrier. It includes a water pump capable of drawing adjustable sample volumes between 22-180 mL into a 250 mL reaction vessel. Upon the addition of 5 mL of phosphoric acid to the vessel, the sample is sparged with helium (He) gas at a rate of 45 mL/min for 16 min. The desorbed CO 2 from the sample is then carried along with He through a series of traps: water vapor traps at –75 °C, a sulphur (SO x ) trap containing silver wires at 650 °C, and two CO 2 traps at –196 °C. The A-DIC is automated via a Python script executed on a PC connected via USB. It demonstrates consistent performance and CO 2 trapping efficiency across batches of up to 10 samples. For contamination study, the CO 2 gas collected is transferred to graphitization units to be converted into graphite for AMS analysis.