An improved setup for radiocarbon analysis of water-soluble organic carbon in environmental matrices

This paper presents an improved setup for radiocarbon analysis of water-soluble organic carbon based on wetchemical oxidation as installed at the Laboratory for the Analysis of Radiocarbon with AMS (LARA) at theUniversity of Bern. The implementation of a non-dispersive infrared CO2detector allows more precise and accuratequantification of carbon amounts in samples and establishes the possibility of simple monitoring of the efficacy offlushing and sampling processes. A detailed blank assessment unveiled undesired oxidation of different materialsand sample temperature as critical factors regarding the level of constant contamination. Contamination arising fromoxidation of septum pieces and carbon-based glues in conventional sampling needles was minimized by developinga glass-sintered needle. This new needle was also designed to be longer, reducing the minimum amount of samplesolution needed to 2 mL. The oxidation time and temperature (1 hr at 75 degrees C) were optimized to further decreasecontamination during analyses of samples with carbon amounts of up to similar to 50 mu g. With these improvements, we nowreport low constant contamination levels of 0.62 +/- 0.12 mu g C (with F14C of 0.19 +/- 0.04), whereas the crosscontamination factor was determined to be 0.25 +/- 0.07%.