Progress report on a novel in situ 14C extraction scheme at the University of Cologne

We present initial results of in situ C-14 system blank and calibration sample measurements obtained using the in situ C-14 extraction scheme developed at the University of Cologne. The C-14 extraction scheme specifically exploits the phase transformation of quartz to cristobalite in order to quantitatively extract the carbon as CO2 and follows a scheme that is different to that of existing extraction systems. Features are offline furnace extraction, single pass catalytic oxidation using mixed copper (I,II) oxide as catalyst, the use of UHV-compatible components and of vacuum annealed copper tubing. The design allows a relatively rapid sample throughput - two samples per day as opposed to the current 2 days per sample that can be done on other lines - and can accommodate samples ranging between 0.5 and 4 g of clean quartz. Following extraction and cleaning, the CO2 gas is measured using the gas ion source of the MICA-DAS AMS facility at ETH Zurich. The extraction system yields low systems blanks (10(+16)/(-10) x 10(3) atoms C-14, +/- 1 sigma) and the initial results indicate that further improvements are achievable. Measurements of the CRONUS-A standard sample show a good reproducibility and results are consistent with published values. We also present the first in situ C-14 results for the CRONUS-R standard material. (C) 2015 Elsevier B.V. All rights reserved.