Automated simultaneous measurement of the δ¹³C and δ²H values of methane and the δ¹³C and δ¹⁸O values of carbon dioxide in flask air samples using a new multi cryo‐trap/gas chromatography/isotope ratio mass spectrometry system

Abstract

The system has been in routine operation at the MPI-BGC since 2012. Consistency of the data and compatibility with results from other laboratories at a high precision level are of utmost importance. A high sample throughput and reliability of operation are important achievements of the presented system to cope with the large number of air samples to be analyzed. Copyright © 2016 John Wiley & Sons, Ltd.

Interlaboratory comparison of <i>δ</i><sup>13</sup>C and <i>δ</i>D measurements of atmospheric CH<sub>4</sub> for combined use of data sets from different laboratories

“…In this study, the term "calibration" means to measure a laboratory gas (for instance a laboratory working standard gas that is routinely compared with samples) against a standard at higher hierarchy level and to assign to that working standard a δ 13 C-CH 4 or δD-CH 4 value traceable to the standard scale. In principle, all measurements at individual laboratories intend to ultimately anchor their working standards and sample gases to the VPDB or VSMOW scale using the RMs provided by the International Atomic Energy Agency (IAEA) or National Institute of Standards and Technology (NIST; Coplen et al, 2006;Brand et al, 2014). However, since RMs and recommended calibration methods for measurements of δ 13 C-CH 4 and δD-CH 4 in air have not yet been provided (Sperlich et al, 2012, individual groups have developed their own calibration strategies.…”

“…This concept has been taken into account in some laboratories; a working standard is calibrated for δ 13 C-CH 4 and sample measurements are referenced by comparison with measurements of that working standard processed in the same manner (e.g. Brand et al, 2016). Despite intentions of best traceability to RMs, the variety of calibrations has resulted in diverse realizations of the VPDB scale across δ 13 C-CH 4 measurement programmes.…”

“…Despite intentions of best traceability to RMs, the variety of calibrations has resulted in diverse realizations of the VPDB scale across δ 13 C-CH 4 measurement programmes. As in Table 1, the different RMs that have been applied to δ 13 C-CH 4 calibration include NBS-19 (limestone), IAEA-CO-9 (barium carbonate), LSVEC (lithium carbonate) and RM 8562-8564 (CO 2 ); see Coplen et al (2006), Brand et al (2014) and Sperlich et al (2016). It is also noted that uncertainties of assigned values for these RMs range up to a few tenths per mille and the assigned values have been revised over time , which might have complicated the realization of the standard scale at each labora-tory.…”

“…The GC-IRMS system at the Institute for Marine and Atmospheric research Utrecht (IMAU) has been described by Brass and Röckmann (2010). The measurement reproducibility is estimated to be 0.07 and 2.3 ‰ for δ 13 C-CH 4 and δD-CH 4 , respectively.…”

“…Later, a method based on a continuous-flow gas chromatography isotope ratio mass spectrometry (GC-IRMS) technique combined with combustion and pyrolysis furnaces became available (Merritt et al, 1995;Burgoyne and Hayes, 1998;Hilkert et al, 1999), which dramatically reduced time and effort in the laboratory and likewise the amount of sample air required (now typically 100 mL STP ). Such systems are now used in most laboratories worldwide to acquire δ 13 C-CH 4 and δD-CH 4 data in the current and past atmosphere (Rice et al, 2001;Miller et al, 2002;Sowers et al, 2005;Ferretti et al, 2005;Morimoto et al, 2006;Fisher et al, 2006;Umezawa et al, 2009;Brass and Röckmann, 2010;Sperlich et al, 2013;Schmitt et al, 2014;Bock et al, 2014;Brand et al, 2016;Röckmann et al, 2016). Although these systems use a similar measurement principle, they vary in the use of pre-concentration of CH 4 in sample air, GC separation and combustion/pyrolysis, data corrections and in the specific IRMS instrument among laboratories (see Schmitt et al, 2013, Sect.…”