I am attempting to freeze-dry treated blood samples at 5mTorr however the shelf temperature is at RT and as a result the samples are 'bubbling' when the vacuum is pulled. Any suggestions to how I can solve this without lowering the shelf temperature (as it can't be done on this machine!). Thanks
Hello Jessica,
Please freeze your sample (in -80C refrigerator or dry ice/EtOH bath) before placing inside the freeze dryer chamber.
I froze whole blood overnight at -80C before I lyophilized it as a thin film about 5mm thick (the thinner the layer the better). Place an insulating layer under and/or around the vessel you are freeze drying the sample in. Don't use Styrofoam under vacuum because it distorts. I used cardboard (corrugated) and cork insulation that I ran through several freeze dry cycles first. The insulation reduces the heat transfer to the sample and prevents the melt-back which will cause frothing or bubbling. Also protect the samples from light during freeze drying, even a small amount of added energy from ambient light can cause the sample to thaw. I transferred the samples immediately from -80C into the vacuum chamber with the refrigeration coils cooled to about -50C.
Hi Jessica,
Agree with Syed above; if you freeze your sample very well and it is still frozen when you place the sample on the freeze dryer, it should remain frozen and lyopilize to powder under good vacuum. If, however, you do not have the optimum vacuum on your system, the sample may thaw during the freeze drying process.
So, make sure it is completey frozen and check your vacuum and make sure the pump is achieving a good operating vacuum.
Best,
Hediye.
Jessica Powell
Hi Jessica
What do you mean by bubbling? Is it about the trace of water evaporation (in the form of circles) on the surface of the film?
Do you have any images which show this phenomenon clearer?
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