Dear Alexander,

That’s great, I’ll have a good look at that! 



Hubert Vonhof
Max Planck Institute of Chemistry
Hahn-Meitnerweg 1
55128 Mainz 
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+49 6131 3056605
+49 176 64460553

On 16 Jan 2018, at 09:25, Knohl, Alexander <[log in to unmask]> wrote:

dear Hubert,

there are also two more papers on that subject in RCM.

Knohl A, Werner RA, Geilmann H, Brand WA (2004): Kel-FTM discs improve storage time of canopy air samples in 10-mL vials for CO2-delta C-13 analysis. Rapid Communications in Mass Spectrometry 18:1663-1665

Tu, K. P., Brooks, P. D. and Dawson, T. E. (2001), Using septum-capped vials with continuous-flow isotope ratio mass spectrometric analysis of atmospheric CO2 for Keeling plot applications. Rapid Commun. Mass Spectrom., 15: 952–956. doi:10.1002/rcm.320

best wishes,

Alexander Knohl
Professor of Bioclimatology
Faculty of Forest Sciences
University of Goettingen
Büsgenweg 2, 37077 Göttingen, Germany

phone:  +49 551 39 33682
fax:    +49 551 39 9619
email:  [log in to unmask]

Am 16.01.2018 um 02:37 schrieb John Hunt:
Dear Hubert
There is an indication that pre-treating the exetainer septa by heating can reduce the exchange of vial CO2 with the ambient atmosphere. Have a look at Midwood et al 2006, Collection and storage of CO_2 for ^13 C analysis: an application to separate soil CO_2 efflux into root- and soil-derived components. Rapid Comms in Mass Spec. 20: 3379-3384.
*Dr. John Hunt*
Manaaki Whenua – Landcare Research
*T* +64 3 321 9703 *| M *+64 21 298 8758
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Manaaki Whenua - Landcare Research <>
*From:*Stable Isotope Geochemistry [mailto:[log in to unmask]] *On Behalf Of *Mihai Lefticariu
*Sent:* Tuesday, 16 January 2018 1:35 p.m.
*To:* [log in to unmask]
*Subject:* Re: [ISOGEOCHEM] septa for exetainer vials
We have been using the standard Labco septa on the 12 ml vials for the past 7 years and, leaving aside leaky vials, acid with air bubbles, or small amounts of air introduced during He flush/fill or even regular analysis, the only time we saw consistent m/z 44, 45, and 46 backgrounds higher than 20 mV was when the carrier He itself was contaminated with air either from the beginning (tank) or somewhere along the line. How does the chromatogram look like when you run vials filled only with He? Cheers. Mihai
Dr. Mihai Lefticariu
IRMS Scientist
Mass Spectrometry Facility
Neckers 103
Southern Illinois University Carbondale
Carbondale IL 62901
*From:*Stable Isotope Geochemistry <[log in to unmask] <mailto:[log in to unmask]>> on behalf of Vonhof, Hubert <[log in to unmask] <mailto:[log in to unmask]>>
*Sent:* Monday, January 15, 2018 8:27:57 AM
*To:* [log in to unmask] <mailto:[log in to unmask]>
*Subject:* [ISOGEOCHEM] septa for exetainer vials
Dear List members,
We have recently started a series of experiments to run small CO2 samples on a GASBENCH system. In doing so, we observe an effect that we interpret to be the release of small amounts of background CO2 from the standard exetainer septa. To reduce the CO2 background that this causes, we wanted to experiment with different septa. Does anyone have experience with other-than-standard exetainer septa in relation to reducing the CO2 background in the exetainers?
With kind regards,
Hubert Vonhof
Max Planck Institute of Chemistry
Hahn-Meitnerweg 1
55128 Mainz
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