Thread: lyophilization

Hallo all,

can anyone explain me this:

"to have a good sublimation of the freezed product, the product itself needs to be on a higher energy level then the environment around it"

I think they mean that you need to put energy in your product and thus the product itself needs to be on a higer energy level.
Or is there another reason why they state this?

besides that: can you have sublimation of a product of the energy around the product is higher?
I think yes, because the environment around the product can then put his energy in the product and thus cause sublimation, but is this correct? It seems a bit strange and a circle movement (=> energy from outside in the product to sublimate it, and by sublimating it you will get vapor with a lot more enery outside the product and thus making the energylevel outside higher again (note that this is in a closed environment, otherwise the engery could go away...?)


any ideas?

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My humble opinion, for what it's worth, is that your quoted statement is so much nonsense. I have worked with lyophilization in several laboratories and I can tell you that no one gives a hoot about energy levels. You simply do the task and go on to the next step.

My guess is that the author of your statement is merely trying to appear very smart. His remark is of no help in actually getting the work done. If you want to consider the matter further, just think in terms of normal evaporation of a liquid. Energy considerations of lyophilization are no different than they are for this familiar phase change.

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Originally Posted by luci

Hallo all,

can anyone explain me this:

"to have a good sublimation of the freezed product, the product itself needs to be on a higher energy level then the environment around it"

I think they mean that you need to put energy in your product and thus the product itself needs to be on a higer energy level.
Or is there another reason why they state this?

besides that: can you have sublimation of a product of the energy around the product is higher?
I think yes, because the environment around the product can then put his energy in the product and thus cause sublimation, but is this correct? It seems a bit strange and a circle movement (=> energy from outside in the product to sublimate it, and by sublimating it you will get vapor with a lot more enery outside the product and thus making the energylevel outside higher again (note that this is in a closed environment, otherwise the engery could go away...?)


any ideas?

If the product is left unheated, it may freeze because some of the product is turning from a liquid to a gas and absorbing energy.

So you may have to heat it if you want it to continue to quickly give off water.

Sincerely,


William McCormick

Originally Posted by SteveF

Â*
My humble opinion, for what it's worth, is that your quoted statement is so much nonsense. I have worked with lyophilization in several laboratories and I can tell you that no one gives a hoot about energy levels. You simply do the task and go on to the next step.

My guess is that the author of your statement is merely trying to appear very smart. His remark is of no help in actually getting the work done. If you want to consider the matter further, just think in terms of normal evaporation of a liquid. Energy considerations of lyophilization are no different than they are for this familiar phase change.

Â*

I have worked with lyophilization and yeah, I know how it works, any monkey can work with freezedrying equipment. Its not hard, you simple put the samples in it and let the machine do its work.

But I want to know more about the physics behind it and how the proces really works and then you need to start thinking at how the energy is transported etc... hence my question.

And indeed McCormick, that might be a reason.

Suggestions requested.


Re: Non-cake-shape of lyophilized reagents probably associated with the presence of Hepes buffer and seeking explanations/solutions



I tried to lyophilize antibody-coated colloidal gold particles in the buffer containing 300 mM Hepes/150 mM NaCl/80 mM MgCl2/5% Sucrose but often encountered a problem of not having a good cake-shape lyophilized components in a 1.5 ml eppendrof tube (with 100 ul of original reagents). The eutectic temperate of the reagents of interest is around 12 C. The product temp was set as low as -43 C (having tried -18 c, -35 C as well) prior to and during the process of first phase of lyophilization. I observed that during the cause of the lyophilzation of first phase, the very top surface of the frozen portion appeared being dried well without deformation, but the lower portion often collapsed. It appears that the surface of the collapsing portion melted and formed a film-like layer of liquid during lyophilization. Occasionally (rarely), under the same conditions (set at -35 C), a very good cake-shape of dried stuff formed but I was unable to reproduce reliably; and I don’t know why.

I have done experiments testing individual components for the possible causing factor(s). It appears that the Hepes is probably the primary suspect. The results of two experiments pointed to this conclusion: (1) the good cake-like shape of 5% sucrose alone was disrupted in the presence of hepes (300 mM) and (2) during the drying process of by warm air blowing, the hepes solution appeared forming a film-like dried surface (i.e., the surface appears to be dried but not the deeper layer my experiments) preventing/prohibiting the lower portion from being dried as fast as it was initially. Unfortunately, I may need to stick with hepes of such a concentration as a buffer for my specific applications.


There are at least two reasons I have been trying to solve this non-cake shape problem: (1) the collapsed lyophilized stuff apparently absorb moisture much faster than the one with well cake-shape (within a couple of minutes in the environment of 40-50%, it melts to form a jelly form; the cake-shape one takes much longer time), and (2) it does not look nice in terms of its looking. The first one is the main issue.


Any explanations and possible solutions would be much appreciated.


Thank you

Jason
email: jason.jal22@gmail.com