Tuneable Infrared Laser Dual Absorption Spectroscopy (TILDAS) for CO2 Clumped Isotopes

The laboratory is equipped with a TILDAS system (TILDAS-FD-L2, Aerodyne) that is able to measure the CO₂ isotopologues ¹²C¹⁶O¹⁶O, ¹³C¹⁶O¹⁶O, ¹³C¹⁸O¹⁸O, ¹²C¹⁸O¹⁶O and ¹²C¹⁷O¹⁶O within two selected frequency windows at high precision. The sample gas is diluted in pure nitrogen to reduce the necessary sample size. Consecutive measurements of sample and reference gas allow the determination of δ¹³C, δ¹⁸O and with a secondary calibration ∆₆₃₈ (comparable to ∆₄₇ in mass spectrometry). The instrument also holds the potential for analysis of δ¹⁷O. The advantage of the TILDAS system is the fast analysis with about 30 minutes per replicate analysis for ∆₆₃₈ and a simplified sample processing.

Currently, 10 mg of carbonate is required per replicate analysis. The carbonate sample is reacted with phosphoric acid at 90°C and the evolving CO₂ gas subsequently purified (Weise and Kluge, 2020). Together with the sample we measure in-house standards (Cararra marble, Merck CaCO₃, Merck Li₂CO₃) and the accepted ETH standards (ETH1-4).

CO₂ clumped isotope analysis can be applied to research questions in the field of carbonate thermometry, palaeothermometry, mineral formation studies and hydrothermal system assessment, CO₂ source identification, paleo-biology, tectonic studies and beyond.