Dear Sir. Concerning your issue about the effective method for collection and storage of gas (~1ml) from septum bottles. Biogas is usually pumped or compressed to the operating pressure required by specific applications and then metered to the gas use equipment. Prior to this, biogas may be processed to remove moisture, H2S, and CO2, the main contaminants in dairy biogas, in which case the biogas becomes biomethane (see Chapter 3). (Partial removal of contaminants, particularly H2S, will yield an intermediate product that we refer to in this report as partially upgraded biogas). Depending on applications, biogas may be stored either before or after processing, at low or high pressures I think the following below links may help you in your analysis:

https://jyx.jyu.fi/dspace/bitstream/handle/123456789/36767/URN:NBN:fi:jyu-2011100611506.pdf?sequence=1

http://suscon.org/pdfs/cowpower/biomethaneSourcebook/Chapter_2.pdf

http://www.airproducts.com/~/media/files/pdf/company/safetygram-10.pdf

http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1467&context=abe_eng_conf

Thanks

 How long are you storing before analyzing?

Did you consider to perform your analysis "at-line", without any storage? Depending on your analytes of interests, the storage of small gas samples might be difficult without changing the composition.

Thank you for your responses,

I will be storing samples for a maximum of a week before analysis. I will be using a GC located outside the laboratory away from the incubated shaker in which this experiment takes place. Therefore, I need to draw ~1ml from 30 septum bottles several times and store for later analysis.

Firstly there are special bag for biogas storing , It is called the tadler bag for biogas storage.

Secondly to follow the ananlyses through the GC it is necessary to recover the sample of the biogas once or twice a week.

Thirdly during the biogas collection, it is ensured that there are no leaks in the digester connection system with the storage tank.

Fourthly after biogas collection, it is preferably to place the bag in a thermostat to avoid the temperature influence, and to move directly after sampling to the apparatus of the GC for the analyzes.

Fifthly during the analysis to take one mL using syringe:

-You put a T to connect the valve with the syringe

-Opens the valve connect with the bag and you leave part of the biogas out

-After the release of certins volume you recover the biogas with the syringe and you put it directly in the GC.

- the GC will be ready

Thank you for your replies. Much appreciated.