Standardization for 13 C-13 C clumped isotope analysis by the fluorination method.

For typical analysis of natural samples, scrambling in the ion source can only change the ∆13 C13 C value by less than 0.04‰, which is lower than the current analytical precision (±0.07‰). Therefore, the observed isotopic reordering may have occurred during the fluorination of ethene through the scrambling of isotopologues of ethene but not in the ion source of the mass spectrometer or during the dehydration of ethanol, given the small amount of C1 and C3+ molecules. Thus, we obtained the empirical transfer function ∆13 C13 CCSC  = λ × ∆13 C13 C with a λ value of 1.25 ± 0.01 for ethanol/ethene and 1.00 for ethane. Using the empirical transfer function, the developed fluorination method can provide actual differences in ∆ values.