Dear Sabine,

Please read the following:

CO2 – DISSOLVED

Container: Polyethylene, PTFE or glass. Fill container completely to exclude air. Transport under ice. 

Preservation Temperature: Refrigerate (< 6°C) .

Determine as soon as possible.

Analysis:

Carbon dioxide, dissolved in water, is measured by titrating a sample aliquot with a

solution of NaOH/NaHCO3 to a pH of 8.3 using a phenolphthalein indicator until a

pink colour persists for 30 seconds in the sample aliquot (potentiometric method can also be used).

It is advisable to analyse the sample in the field; if not, then preserve the sample at

lower temperature than collected, and analyse within 24 hours.

Interference: Anions and cations that quantitatively disturb the equilibrium of

carbon dioxide-carbonate. Al, Cr, Cu, Fe are some of the metals with salts that

provide bias high analytical results; amines, ammonia, borate, nitrite, phosphate,

silicate and sulfide also provide positive results. Mineral acids and salts of strong

acids and base should be absent. This method is not applicable in samples containing mine wastes. High total dissolved solids may introduce negative results.

The method detection limit is 1 mg/L. 

Requesting Agency and Date: Environment Canada, September 1978.

Reference: APHA 1975.

http://www.unep.org/gemswater/Portals/24154/pdfs/quality_control/analytical_methods.pdf

See page 13 in the publication contained in the following link:

http://www.epa.vic.gov.au/~/media/Publications/IWRG701.pdf

Methane Dissolved-

Container: Glass with PTFE lined lids or septum caps 

Sampling & Transport: Fill container to completely exclude air. Transport under

ice For purge and trap analysis collect samples in duplicate or triplicate in 40 mL

vials with PTFE faced septum.

Preservation: Acidify to pH < 2 with H2SO4, HCl or solid NaHSO4.

Preservation Temperature: Refrigerate (< 6°C) Store in area free of solvent fumes. 

See page 15 in the publication contained in the following link:

http://www.epa.vic.gov.au/~/media/Publications/IWRG701.pdf

Hoping this will be helpful,

Rafik

You could use ionized silver to inhibit the growth of bacteria.

water samples should be stored at 40 C for further analysis.

Water sample should be store < 4 degree centigrade. For dissolved CO2 and CH4, Laser Raman Spectroscopy found to be appropriate and  technique.