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UC Davis Plant Sciences


Analysis of Carbon Dioxide (CO2) by GasBench-IRMS

The SIF provides δ13C analysis of CO2 in headspace vials using a Thermo Scientific GasBench interfaced to a Delta V Plus IRMS.

 

Analysis of 13C in Carbon Dioxide

Stable isotope ratios of carbon (δ13C) in carbon dioxide are measured using a ThermoScientific GasBench system interfaced to a ThermoScientific Delta V Plus isotope ratio mass spectrometer (ThermoScientific, Bremen, Germany).  CO2 is sampled by a six-port rotary valve (Valco, Houston TX) with either a 100 µL, 50 µL, or 10 µL loop programmed to switch at the maximum CO2 concentration in the helium carrier gas.  The CO2 is then separated from N2O and other residual gases by a Poroplot Q GC column (25m x 0.32mm ID, 45°C, 2.5 mL/min). A pure reference gas (CO2) is used to calculate provisional delta values of the sample peak.  Final δ13C values are obtained after adjusting the provisional values for changes in linearity and instrumental drift such that correct δ13C values for laboratory reference materials are obtained.  At least two laboratory reference materials are analyzed with every 10 samples.  Laboratory reference materials are calibrated directly against NIST 8545. Final δ13C values, delivered to the customer, are expressed relative to the international standard V-PDB (Vienna PeeDee Belemnite)

 

Limit of Quantitation and Long-term standard deviation for CO2 Analysis by GasBench-IRMS

CO2 : Limit of Quantitation: approx. 150 nanomoles

           Long-term standard deviation: 0.1 ‰

 

Maximum measurable CO2 concentrations (without sample dilution or subsampling) is 50,000 ppm.  Actual sample measurement limits are dependent upon both gas concentration and isotopic enrichment.  Please contact us if you intend to submit 13C-enriched samples at gas concentrations more than ten times that of ambient CO2 concentration.








 
e-mail: sif@ucdavis.edu | phone: 530-752-8100 | fax: 530-752-4361
UC Davis Stable Isotope Facility | Department of Plant Sciences
One Shields Avenue | Davis, California, 95616 | USA