Isotopic analysis of atmospheric CO2 (δ13C and δ18O)
High precision analysis of oxygen and carbon isotopic ratios of CO2 in air
High precision analysis of oxygen and carbon isotopic ratios of CO2 in air continues to be a major activity of the BGC-IsoLab since the initial experiments at the turn of the century.
BGC-AirTrap: Home-made extraction system establieshed in 2000 that extracts CO2 from air samples contained in 1L and 5L glass flasks. At a flow rate of 60 ml/min ~ 600 ml of sample are consumed per measurement.
BGC-AirTrap: Home-made extraction system establieshed in 2000 that extracts CO2 from air samples contained in 1L and 5L glass flasks. At a flow rate of 60 ml/min ~ 600 ml of sample are consumed per measurement.
From a Valco Multiport valve the air passes through a mass flow controller over an ethanol/dry ice (-70 °C) water trap into a LN2 (-196 °C) trap that removes CO2 and N2O at a pressure of about 100 mbar. Upon thawing the trapped CO2 is analysed on one of two MAT252 isotope ratio mass spectrometers (Matty and Cora) equipped with dual inlet systems.
MAT252 IRMS “Matty” has been in operation since 1998 (left), and MAT252 IRMS “Cora” (Carbon and Oxygen Ratio Analyser) since 2002. Both instruments are equipped with the BGC-AirTrap, and together they have the capacity to analyse 26 sample- and 10 standard- and QC-measurements per day.
MAT252 IRMS “Matty” has been in operation since 1998 (left), and MAT252 IRMS “Cora” (Carbon and Oxygen Ratio Analyser) since 2002. Both instruments are equipped with the BGC-AirTrap, and together they have the capacity to analyse 26 sample- and 10 standard- and QC-measurements per day.
Q/C chart of “Cora” covering all measurements since 2002 of the Q/C syn. air tank “Westf 10-2000”. The data is given on the JRAS-06 scale realisation of the VPDB scale.
Q/C chart of “Cora” covering all measurements since 2002 of the Q/C syn. air tank “Westf 10-2000”. The data is given on the JRAS-06 scale realisation of the VPDB scale.
Performance charts of our quality control measurements illustrate the measurement precision of Cora. The single-analysis precision of “Cora” is better than 0.02 and 0.03 ‰ for δ13C and δ18O measurements, respectively, since 2002. The single-analysis precision of „Matty“ is slightly worse, with 0.05 ‰ and 0.08 ‰ for for δ13C and δ18O measurements, respectively. This is due to the fact that “Matty” analyses all kinds of air samples (e.g. air from soils) that may be contaminated with VOCs, while “Cora” is dedicated to clean atmospheric air samples, only.
Storage aspects have been described in:
Rothe, M.; Jordan, A.; Brand, W. A.: Trace gases, δ13C and δ18O of CO2-in-air samples: Storage in glass flasks using PCTFE seals and other effects. In: Proceedings of the 12th IAEA/WMO meeting of CO2 experts, Toronto, Sept. 2003, pp. 64 - 70 (Eds. Worthy, D.; Huang, L.) (2005)
See also "Central Flask Facility" under "Activities"
Further reading:
Werner, R. A.; Rothe, M.; Brand, W. A.: Extraction of CO2 from air samples for isotopic analysis and limits to ultra high precision δ18O determination in CO2 gas. Rapid Communications in Mass Spectrometry 15, pp. 2152 - 2167 (2001)
Ghosh, P.; Brand, W. A.: The effect of N2O on the isotopic composition of air-CO2 samples. Rapid Communications in Mass Spectrometry 18 (16), pp. 1830 - 1838 (2004)
Ghosh, P.; Patecki, M.; Rothe, M.; Brand, W. A.: Calcite-CO2 mixed into CO2-free air: a new CO2-in-air stable isotope reference material for the VPDB scale. Rapid Communications in Mass Spectrometry 19 (8), pp. 1097 - 1119 (2005)
