I am trying to figure out how quickly oxygen goes back into degassed E3 medium (essentially water with some salts). Degassing takes place with 5 cycles of 1 minute degassing in vacuum and 1 minute regassing with Nitrogen/Argon. Does anyone know how fast reoxygenation would be? I am using 50ml falcons filled up to 50 mls. I parafilm the falcons too after vacuuming.
Hi Nikolaos Stefanidis ,
I found following equation in Liu et al. (2019; Article Investigation and Modeling of Gas-Liquid Mass Transfer in a ...
):kLa = - ln(1-CL/CS) / t
where, kL is liquid film mass transfer coefficient (m h-1), a is gas-liquid interfacial area per unit volume (a=A/VL) (m-1), A is the mass transfer area (m2), VL is the liquid working volume (m3), kLa is overall volumetric mass transfer coefficient (h-1), CS is the saturated DO concentration in the liquid (mol m-3), CL is the DO concentration in the bulk liquid (mol m-3), and t is time (h).
We can rearrange the above equation for t and, assuming a kLa value of 0.7 hr-1, estimate the time it takes to reach an oxygen concentration 99 % of CS. The value I got is 6.6 hr.
Now we do not know the kLa value for your system so it is necessary to carry out experiments to determine it. The CS value can be predicted here: http://www.colby.edu/chemistry/CH331/O2%20Solubility.html. For the rest you need a calibrated dissolved oxygen probe, a thermometer and a stopwatch.
Hope this helps?
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