After 10 days, 3-μmol CO2 samples in containers having glass stopcocks with Viton® or FETFE O-rings were enriched in 18O by 1.5% as a result of absorption by the elastomer; this amount of enrichment is ∼20 times greater than the precision of δ18O measurements of most laboratories. No change in 13C content was observed. Increasing the sample size to 100 μmol resulted in an 18O enrichment of 0.2% and did not affect the 13C content.
Caution needs to be exercised in selecting sample containers for CO2 isotope-ratio samples of < 200 μmol. If stopcocks are used in construction of containers for such samples, the use of all-glass stopcocks with Apiezon N® hydrocarbon-based grease will eliminate the fractionation of oxygen isotopes.
Additional publication details
|Publication Subtype||Journal Article|
|Title||Caution on the use of Viton® or FETFE® O-rings in carbon dioxide sample containers for δ180 analysis|
|Series title||Chemical Geology: Isotope Geoscience Section|
|Online Only (Y/N)||N|
|Additional Online Files (Y/N)||N|