Hello. I'm starting work on analytical electrochemistry. The most common way of degassing the solution is bubbling nitrogen. However, what about vacuum? Can it be as potent? Could not find info on that anywhere.
Thank you very much!
Alex.
The best is to purge the solution with Ar under vigorous agitation. Ar has a higher density than air and stays longer in the cell. Use the purging gas presaturated with your solvent in order to avoid an excessive solvent evaporation.
I often degas solutions for 10-15 min by bubbling nitrogen through it.
i have also heard of freeze pump thaw method or something along those lines but im not sure what that entails.
lastly, i think certain aluminium or copper compounds can deoxygenate a solution by passing solution through column of said material.
Havent really heard of vacuum degassing
Nitrogen. I used this gas over 5 years and had no problem. Also, ensure you have a regulator to control the pressure.
Thank you all for the answers! I know nitrogen degassing is the commonly used method, but I'm curious if I can use vacuum, and if I cannot - then why.
My guess is by vacuum you are assuming youd decrease the solubility of the gas dissolved in the solution. I think the reason you can't use vacuum alone is because you wouldnt completely get rid of all the gas dissolved in the solvent... just a guess
As Greg Petruncio said. Also, you would need to keep in mind that vacuum will result in lowering the solution temperature as well, and depending on volume and vapor pressures, could change the concentration of any analyte. If you really want to drive more gas out of the the solution than nitrogen, you can use He (or H2) which have lower solubility than nitrogen (or CO2, or argon). The main reason to use nitrogen is it's cheap, and not electrochemically active in most situations.
The best is to purge the solution with Ar under vigorous agitation. Ar has a higher density than air and stays longer in the cell. Use the purging gas presaturated with your solvent in order to avoid an excessive solvent evaporation.
Dear Dr. Oleksiy Krupin,
here below are suggested some methods of degassing:
- Freeze-Pump-Thaw This is the most effective methods for solvent degassing. A solvent in a sealed Schlenk or heavy wall sealed tube is frozen by immersion of the flask in liquid N2. When the solvent is completely frozen, the flask is opened to the vacuum (high vacuum) and pumped 2-3 minutes, with the flask still immersed in liquid N2. The flask is then closed and warmed until the solvent has completely melted. This process is repeated (usually three times) and after the last cycle the flask is backfilled with an inert gas. Degassed solvent in a sealed Schlenk flask can usually be kept for 1-2 days.
- Atmosphere Exchange Under Sonication Solvents can be roughly degassed by repeated sonication under light vacuum (i.e. house vacuum) for 0.5-1 min and replenishing the atmosphere with an inert solvent. By using 5-10 cycles, degassed solvents for HPLC and some reactions can be obtained quickly.
- Purging Of the methods listed here, purging is the least effective way of degassing solvent, however it is acceptable for some applications, particularly when large amounts of solvent need to be roughly degassed. As it sounds, purging consists of bubbling an inert gas (usually N2 or Ar) through the solvent for 30 min - 1 hour. Care should be taken to prevent solvent evaporation and especially the condensation of water in the solvent by using an appropriate setup.
Source: http://chem.chem.rochester.edu/~nvd/page/how_to.php?page=degas_solvents
Best regards, Pierluigi Traverso
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