Details

Autor(en) / Beteiligte

• Walker, Brett D
• Beaupré, Steven R
• Griffin, Sheila
• Walker, Jennifer
• Druffel, Ellen
• Xu, Xiaomei

Titel

A sealed-tube method for offline δ 13 C analysis of CO 2 via a Gas Bench II continuous-flow isotope ratio mass spectrometer

Ist Teil von

• Rapid communications in mass spectrometry, 2021-04, Vol.35 (7), p.e9040

Ort / Verlag

England

Erscheinungsjahr

2021

Quelle

Wiley Online Library - AutoHoldings Journals

Beschreibungen/Notizen

• The isotopic measurement of environmental sample CO via isotope ratio mass spectrometry (IRMS) can present many analytical challenges. In many offline applications, exceedingly few samples can be prepared per day. In such applications, long-term storage (months) of sample CO is desirable, in order to accumulate enough samples to warrant a day of isotopic measurements. Conversely, traditional sample tube cracker systems for dual-inlet IRMS offer a capacity for only 6-8 tubes and thus limit throughput. Here we present a simple method to alleviate these concerns using a Gas Bench II gas handling device coupled with continuous-flow IRMS. Sample preparation entails the cryogenic purification and quantification of CO on a vacuum line. Sample CO splits are expanded from a known volume to several sample ports and allowed to isotopically equilibrate (homogenize). Equilibrated CO splits are frozen into 3 mm outer diameter Pyrex break-seals and sealed under vacuum with a torch to a length of 5.5 cm. Sample break-seals are scored, placed into 12 mL Labco Exetainer vials, purged with ultrahigh-purity helium, cracked inside the capped helium-flushed vials and subsequently measured via a Gas Bench equipped IRMS instrument using a CTC Analytics PAL autosampler. Our δ C results from NIST and internal isotopic standards, measured over a time period of several years, indicate that the sealed-tube method produces accurate δ C values to a precision of ±0.1‰ for samples containing 10-35 μgC. The tube cracking technique within Exetainer vials has been optimized over a period of 10 years, resulting in decreased sample failure rates from 5-10% to <1%. This technique offers an alternative method for δ C analyses of CO where offline isolation and long-term storage are desired. The method features a much higher sample throughput than traditional dual-inlet IRMS cracker setups at similar precision (±0.1‰).