Analytical services: Ξ΄13C and Ξ΄18O of gaseous CO2
The SPA lab uses a GasBench II attached to MAT-253 IRMS for the measurement of Ξ΄18O and Ξ΄13C 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 Ξ΄18O and Ξ΄13C 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 Ξ΄13C and Ξ΄18O.
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.