Clumped isotope analysis of carbonates: comparison of two different acid digestion techniques

RATIONALE The kinetic nature of the phosphoric acid digestion reaction enables clumped isotope analysis of carbonates using gas source isotope ratio mass spectrometry (IRMS). In most laboratories acid digestions are performed at 25°C in sealed vessels or at 90°C in a common acid bath. Here we show that different Δ47 results are obtained depending on the digestion technique employed. METHODS Several replicates of a biogenic aragonite and NBS 19 were reacted with 104% H3PO4 in sealed vessels at 25°C and at 90°C using a common acid bath. The sample size varied between 4 mg and 14 mg. Purification methods that are standard for clumped isotope analyses were applied to the evolved CO2 before meas…