Freeze Dryer vs Speed Vac

Dr Engelbert Buxbaum engelbert_buxbaum at hotmail.com
Wed Mar 26 12:02:41 EST 2003

Greg Pankhurst wrote:

> Hey All
> Just wanted to canvas opinions on the advantages of using a Freeze Dryer
> to dry proteins down over using a Speed Vac.
> My understanding was that the solid -> gas transition was gentler than
> the liquid -> gas transition, and thus you were far less likely to see
> things like oxidation occuring with a freeze dryer. Is this about right
> or am I miles away ??

You can actually use a speed vac for lyophilisation, if you shut the
heating of. The sample will be cooled by evaporation of solvent and stay
frozen. Of course, then you should call it a "slow vac" ;-)

The main advantage of a speed vac is that with very small sample
volumes, and in particular with small amounts of lyophilisate (ie a few
nmol radiolabeled material of high specific activity), you know were
your product is at the end of the run: at the bottom of your tube. In a
lyophilizer, product will be fluffy, small amounts are easily lost.
Also, when redissolving the product, you can use smaller volumes of

On the other hand, for larger volumes of material, conventional
lyophilizers are more efficient.

Oxydation should not happen in either case, as you are working in a
vacuum with little oxygen present. But protein denaturation certainly is
a problem that occurs more readily in a speed vac.

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