Am 14.07.2008, 21:33 Uhr, schrieb Dorit Grunberger
<dorit.grunberger from radiology.ucsf.edu>:
> Saw this online and thought to ask you if it makes sense to hook up a
> speedvac to a lyophilizer both as source of vacuum and no less
> important, a
> cold environment to keep my extract happy. I¹m doing chloroform :
> methanol :
> water extracts of small tissue samples. The total volumes for extraction
> will be small and I was hoping to use a speedvac to dry/concentrate my
> MeOH/H2O phase. It¹s critical for the sample to remain as cold as
> possible,
> since the analysis of contents is done by NMR and we¹re hoping to
> maintain
> integrity of some very easily degradable metabolites (phospho-choline for
> example).
The lyophiliser keeps samples cold by the heat of evaporation that is
constantly removed from the system. As long as your vacuum is strong
enough and the solvent has not evaporated the sample will be at a
temperature well below its freezing point. If there is a problem you
recognise that by your sample melting.
In the SpeedVac the lyophilisation process is speeded up by gently heating
the sample to replace the heat of evaporation, the sample will not be
quite as cold as in a lyophiliser. In addition the residue will be in a
small spot due to the centrifugal force, it will be easier to take it up
in a small volume later. In addition, loss of residue will be smaller
(important e.g. for radioactive samples).
In either case sensitive samples have to be removed immediatly after
complete drying, as they will warm to room temperature (or to operating
temperture in the SpeedVac) once no solvent evaporates anymore.
