Improved Sealed-Tube Combustion of Organic Samples to CO2for Stable Carbon Isotope Analysis, Radiocarbon Dating and Percent Carbon Determinations

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Abstract
The present note deals with the optimization of the combustion of organic materials to CO2 in Pyrex and quartz tubes. The influence of temperature and oxidant on the combustion yield was investigated. Different physical forms of CuO and a CuO/MnO2-mixture were used as oxidants. Possible isotopic effects during combustion were tested by gas isotope ratio mass spectrometry (GIRMS) of the CO2. Excellent results were obtained for combustion in Pyrex at 530 °C using CuO rods mixed with 20% MnO2 as oxidant. The stable isotope results for CO2 prepared with this method were accurate and showed a very good precision of 0.030 %. Applications for which quantitative combustion is a necessity, we suggest the use of CuO powder (< 100 μm) as oxidant and a combustion temperature of 850 °C.