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Skidmore College
Stable Isotope and Palæoclimate Analysis Laboratory

Analytical services: δ13C and δ18O of gaseous CO2

The SPA lab uses a GasBench II attached to MAT-253 IRMS for the measurement of δ18O and δ13C ratios of CO2 in atmospheric air or breath. The sample is introduced into a headspace vial and the GasBench automatically samples CO2 in the vial.

During a run sequence, gas derived from the acid reactions (see Carbonate δ18O and δ13C Isotopes) three each of NBS-19 and LSVEC international standards are used to normalize isotope results using a two-point linear normalization technique. Two NBS-19 limestone samples are run "as a sample" to monitor quality control and long-term performance. Normalized delta values are expressed relative to VPDB for δ13C and δ18O.

Gaseous CO2 rates

Isotope Phase Quantity Measurement Precision Internal External
δ18O, δ13C Gas 20–50 µg ± 0.08 ‰ $6 $10

Sample types: Air, breath, or gas with 400-8000 ppm CO2

Sample requirements: Air (or breath or gas) with 400-8000 ppm CO2 is usually and preferably submitted already in 12 ml labco vials with septate tops. If air samples are submitted in other containers, then an additional charge of $2 is charged for flushing vials with helium and using a gastight syringe to transfer the sample. The increased pressure in the vial from flushing with helium makes introducing the gas problematic.