Introducing a ramped pyrolysis/oxidation‐ ¹⁴ CO ₂ analysis system operated with mobile mo

Abstract

A novel instrument for the thermal degradation of sedimentary organic matter was set up at the Alfred Wegener Institute (AWI) in Bremerhaven, Germany, with the aim of enabling Ramped Pyrolysis/Oxidation‐ ¹⁴ C analysis as direct CO ₂ gas measurement. This is achieved by using self‐constructed multiposition molecular sieve (zeolite) trap systems, which are mobile and compatible with AWI's accelerator mass spectrometer as well as other CO ₂ ‐producing devices. Here we provide a detailed description of the instrument setup, standard operating procedures, data reproducibility, and blank carbon contribution. The total blank of a standard run with a mass of 3.1 ± 0.2 μ gC and an F ¹⁴ C = 0.46 ± 0.03 is comparable to values published for other systems. We use a Bayesian statistical model in combination with the isotope dilution method to calculate the procedural blank and an isotopic mass balance for blank correction. This method is applied to correct F ¹⁴ C values measured for seven fractions of a natural, radiocarbon‐free standard material. The resulting corrected F ¹⁴ C values are indistinguishable from blank gas measurements. Using a range of different standard materials, the thermogram and ¹⁴ C measurement reproducibility are demonstrated. The method presented here constitutes a flexible and time‐saving alternative to cryogenic CO ₂ trapping, facilitates high sample throughput and enables thermal degradation measurements of various sample types, including samples with ultra‐low organic carbon content.