Freeze - Dry Problem

Dear

have problem with a freeze dryer (CRYODOS 50) when the want to freez dry even water after 20 or 30 minutes the ice began melted.

What can be the problem ?

Thanks for your help

Vivien

Dear

No Ideas to help me ?

Regards

Herer are two thoughts.

(1) If your vacuum pump isn't getting the pressure below the triple point of water quickly enough, then solid water can melt to a liquid instead of sublimating to a gas.  Check your pressure.

(2) It helps to ge the sample very cold.  That way you have some time while the temperature of the sample is increasing toward 0C to get the sample into the freeze dryer, seal the chamber and get the pressure below the triple point.  I like to chill my samples in a -80C freezer, but we often use a -40C freezer for production.  If you are freezing at a higher temperature, you are more likely to have trouble wiht water formation prior to acheiving sufficient vacuum to ensure sublimation.

Dear

Thanks for your help, may be i have to change the vacuum pump, the freez Drye it's a CRYODOS 50 (TELSTAR) Do you already use it ?

Regards

No, I am using labconco machines.  Measure your vacuum.

Ok, thanks, i'm purchasing one cvauum sensor to measure the vacuum

Hi,
If you are using the chamber system rather than the manifold system on your freeze dryer, I also cool the chamber unit and the holders.  Like Jonmoulton said, keeping everything very cold is the secret.
I also found that starting up the unit first letting it all get cold etc, then quickly placing the samples/vials in and starting it as soon as possible.  We have a very VERY old unit (about 35+ years old)
Apologies for teh late input to the discussion.

Nic

We use only the manifold. Think i will change the vacuum pump( i already purchase it) and let you know the result.

Thks Nic