A new approach for high-precision triple oxygen isotope analyses of CO2

Detection of small variations in triple oxygen isotope ratios (Δ’17O) of rocks, minerals, and water has opened new applications in the field of isotope geochemistry (1,2). A long-standing problem is extending the approach to CO2 and carbonates because of analytical difficulties getting precise Δ’17O of CO2. Direct measurement of Δ’17O of CO2 by means of high-resolution gas source mass spectrometry has been successfully demonstrated but requires measurement times of days for reaching a precision <10 ppm (3). Here, we present data of high-precision analyses of carbonate-derived CO2 and CO2 from the conversion of air O2 using a tunable infrared diode laser absorption spectroscopy (TILDAS) attached to a custom-built inlet system controlled by free software (PHP, Python, JavaScript, CSS, HTML) and low-cost electronic hardware, i.e., Raspberry Pi. With this device, we now achieve an external reproducibility as small as ±5 ppm. This opens new application fields, of which some will be presented.

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3. G. A. Adnew, et al., Determination of the triple oxygen and carbon isotopic composition of CO2 from atomic ion fragments formed in the ion source of the 253 Ultra High‐Resolution Isotope Ratio Mass Spectrometer. Rapid Commun. Mass Spectrom. 33, 1363-1380 (2019).