Many people use a MrFrosty freezing chamber (or something similar) for freezing their cells.
Written on the side of the chamber it instructs the user to change the isopropanol inside every 5 freeze-thaw cycles.
Why is this? I can't imagine that anything changes chemically with the isopropanol and as long as I make sure that water does not contaminate the inside of the chamber, then what is the problem in just making sure that the isopropanol is the correct volume and in potentially using it indefinitely.
The very same question puzzled me for quite some time, but I finally figure out the reason why we have to change isopropanol by discussing it with a technical specialist from ThermoFisher Scientific. Actually, after several cooling and warming cycles, enough vapor condensation has taken place that much of the alcohol in the reservoir has been replaced by water, which affects the heat capacity of the assembled unit such that the cooling rate can be significantly affected. Results may vary, of course, depending on your specific operating conditions as well as the robustness of your cell lines. Ultimately you may find that you can get away with more than 5 cycles with perfectly adequate cell viability. Hope this helps.
Isopropanol has moderate effect on both polycarbonate and polyethylene materials that are a part of the Frosty containers. Although it would take a long time for any effect to be seen on the polymers, I suspect this is the reason that the company requests you to change the isopropyl alcohol every once in a while. I am sure you could get away with changing the isopropanol much less frequent that once in 5 uses.
Alternatively, you could remove the isopropanol into a glass bottle when the system is not in use to prolong its usage.
The very same question puzzled me for quite some time, but I finally figure out the reason why we have to change isopropanol by discussing it with a technical specialist from ThermoFisher Scientific. Actually, after several cooling and warming cycles, enough vapor condensation has taken place that much of the alcohol in the reservoir has been replaced by water, which affects the heat capacity of the assembled unit such that the cooling rate can be significantly affected. Results may vary, of course, depending on your specific operating conditions as well as the robustness of your cell lines. Ultimately you may find that you can get away with more than 5 cycles with perfectly adequate cell viability. Hope this helps.
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