Below should read 'septa thickness' not 'septa size'

Chris Boreham

-----Original Message-----
From: Boreham Chris 
Sent: Friday, 3 October 2008 7:03 AM
To: 'Stable Isotope Geochemistry'
Subject: RE: [ISOGEOCHEM] storage of gas samples [SEC=UNCLASSIFIED]

Hi Georg

I'm currently involved in a demonstration-scale geosequestration of CO2
project where one module of the monitoring and verification protocol involves
multiple soil gas surveys. The method involves taking soil gases from 1 m
below the surface into gas bags. The supplied apparatus from SGE uses small
200ml gas bags with a simple septa through which you extract the sample for
analysis. This proved an effective way to store gas samples for months but
once the septa was pieced, almost complete exchange with air occurred after 2
weeks. We found that 500ml (smallest size we could buy) 5-layered gas bag
with a plastic valve assembly was more reliable for long term storage for
re-analysis (the cost of these bags was not that much more than the smaller
simpler ones).


We also tried glass bottles with screw caps (pre-drilled small hole in the
cap) and found that a septa size of 6 mm (supplied was 3 mm) was required for
long term storage after the septa was punctured.

Chris Boreham
Geoscience Australia
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-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Georg Guggenberger
Sent: Friday, 3 October 2008 12:01 AM
To: [log in to unmask]
Subject: [ISOGEOCHEM] storage of gas samples

Hi everyone,

we are planning to sample soil CO2 efflux using a closed chamber. Gas
samples will have natural abundance (control) and slighty enriched in 13C
(expected is about 2-20 o/oo after a pulse-labelling). Since the experiments
will be carried out in Ethiopia we need to store the samples for up to 8
weeks until analysis.

Does anybody have an idea how to do this best? Vaccutainers are obviously
not suitable for longer-term storage of gas samples.
Any suggestion will be welcome.

Thanks,
Georg


Georg Guggenberger
Institute of Soil Science
Leibniz University Hannover
Herrenhäuser Str. 2
30419 Hannover
Germany

phone: +49-511-7622623 
alternative phone: +49-511-7622622
fax: +49-511-7625559
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