Dear Mohamad, you can remove the O2 by sparkling with any inert gas like N2 or argon

and you better to explain you question more briefly to be understand well

Mohammad,

There is truly no such thing as 'totally oxygen free' i.e. there is always some (trace) amount of dissolved oxygen. As Ramesh noted, you can flush the solution with N2 or argon. I would suggest bubbling with argon because argon is more dense than atmosphere and will therefore lower the rate of O2 diffusion from atmosphere. I suggest bubbling through your solution, decreasing surface area to volume ratio as much as possible, and stirring vigorously. You'll need a rubber septum that can vent excess gas throughout the degassing (a needle works for us), and prevent O2 diffusion. Make sure to remove the needle before stopping the degassing, and you probably want a slight excess of argon in your head space so there is positive pressure in your reaction vessel. 

Hope that helps,

Scott

Hello everybody,

Following this question. Should be possible to keep a low concentration of Dissolved Oxygen in an experimental tank (with bivalves) by adding CO2 and  O2 at the same time? It seems quite hard to keep low levels of DO while individuals are breathing in a fluctuating way (sometimes individuals stop breathing even several hours).

If someone has already tested something similar i would appreciate advices about the methodology.

Thanks in advance!

Sergio

Dear Sergio, may be you can purge (O2) gas into the solution at certain flow rate with maintaining certain temperature, but along with CO2 I don't have any idea ! 

you can add Na2SO3 to the solution.

I would flush the water column with N2 (in a water tank with a small surface-to-volume ratio, ideally covered) and counter-balance the pH changes in the water column with a controlled flow of CO2.

Sodium sulfite is primarily used in water treatment as an oxygen scavenger agent, to treat water being fed to steam boilers to avoid corrosion problems

Dear all,

I have a similar problem in my anaerobic fermentations (glucose fermentation by C.beijerinckii). I flush the fermenter with N2 (0.5 l/min) entire time and stir.

I prepare my anaerobic media accordingly so that there is no dissolved oxygen in the begining of the fermentation. However, during exponential growth phase, dissolved oxygen level increases drastically, up to 60%. The problem is not the probe nor the equipment. I observed the same pattern in different setups (Aplikon fermenters and microreactor fermentations).

Does anyone experience a similar thing?

You suggest a reducing agent such as the sulfides. Is there any paper about the effect of the reducing agent on the fermentation?

Regards,

Hi Cansu - I don't know if this is useful for you, but in the context of in vitro fermentation assays with rumen microbiota, there has been some research suggesting these reducing agents consisting of sulphides may impair microbial growth of certain fermenters (Fukushima et al., 2003) so Mould et al. (2005) recommend using cysteine HCl as a reducing agent instead.

Papers referenced:

Fukushima, R.S., Weimer, P.J., Kunz, D.A., 2003. Use of photocatalytic reduction to hasten preparation of culture media for saccharolytic Clostridium species. Bras. J. Microbiol. 34, 22–26.

Mould, F.L., Morgan, R., Kliem, K.E. and Krystallidou, E., 2005. A review and simplification of the in vitro incubation medium. Animal Feed Science and Technology, 123, pp.155-172

Dear Camilla,

thank you for the tip. It is worth to try the suggested approach.

Hi Cansu, Where do you suggest that the O2 is coming from? Paul.

Robert Johannes Meier , I think is a wonderful idea, but how much I need to add, do you know, or could you tell me where I can find that information???

thanks in advance so much

The best way is adding of Na2S2O5 - Sodium metabisulfite. Exists commercial catalized form for fast reaction.

Oleksandr Goncharov Do you have a formula or method for calculating the dosing of sodium metabisulfite to water for the removal of dissolved oxygen. I'm trying to figure a ratio for a hydrogeochemical pilot test, and want to make sure I doing it correctly (based on temperature, in particular). Most of the methods I've found only provide information for boiler environments (involving hot water), which is the opposite of what I need. Thanks!

Dear Samantha Smith, you have to add an excess of sodium metabisulfite (pyrosulfite). This reaction is comparatively slow (for room temperature water) and depends on quantity of reagent. You can increase the reaction velocity by stirring of the solution. Anyway, to completely remove the oxygen you have to use at least 0.4-0.5 ml of 33% solution of metabisulfite per 1 liter of water. But it will take about 17 minutes for non-catalized solution. For more fast reaction you can use more pyrosulfite. I did such experiments. You can read more using the following link: https://www.researchgate.net/publication/334671693

You can use the freeze /thaw method to remove dissolved oxygen from a solution. This is the best way to get rid of oxygen. First you freeze your reaction mixture using liquid nitrogen, then pull vacuum for few min while it is frozen. At this temperature your mixture will be a solid and your gasses are still in the gaseous form. By pulling vacuum all the gases can be removed. Then you have to thaw the reaction to room temperature. do the same thing for two more times for accurate results.

About pyrogallic acid + NaOH as oxygen scavenger ― check my post at:

https://www.researchgate.net/post/Can-somebody-recommend-a-method-for-making-48-96-well-plate-anaerobic