Dear Scheibe,

An obvious question perhaps; have you contacted Christ directly, they are a good German engineering company and I am sure you will get a sensible answer from them.  Please note that freezedryinginfo.com is a website of Millrock Technology in USA who are an equipment manufacturer but not in the same league as Christ.

General physical principals to consider:

The sublimation temperature of your solvent is also the desublimation temperature,° so if you have your pressure set such that the sub / desub temperature of the organic is not lower than your condenser temperature, you should be able to collect much of your solvent in the cold trap.  If you make the pressure too low, the cold trap cannot catch the solvent.  Beware, I do not think that (m)any manufacturers publish the temperature performance of their cold traps under load ... normally the best number is published which is the maximum performance with no load.   With T-BuOH you shold be OK as the freezing point is so high at +25°C.  Likewise Cyclohexanone should probably be OK, but I don't have a BP curve under vacuum for this solvent to see the pressure you will need to make it sublime.  Phenol is a solid at room temperature and I do not know it's sublimation properties, BP under vacuum or Delta H s ... I also know that it is quite agressive to plastics, polymers and rubbers like o-rings and gasgets, so you must check on chemical compatibility with the equipment manufacturers here.

You're correct about pumps and the like.  For evaporation products which have a similar construction to a freeze dryer, Genevac is the only one I'm aware of that offers a system suited to evaporation of agressive chemical vapours, and flammables as they have an inert gas purge and put flame arresors in the vacuum line, this creates the safest system of which I'm aware, but it's expensive and not ideal for traditional freeze drying applications.

Kind regards,

Rob

Thank you for the information.

I have already send information to Christ and will post a feedback here.

In our research group we we freeze-dry t-BuOH:water solutions (various ratios) on a Christ Gamma 2-16 LSC Freeze Dryer.

http://dx.doi.org/10.1016/j.ijpharm.2015.10.029

http://dx.doi.org/10.1016/S0022-3549(15)00186-0

Kind regards

Ann-Christin

Thank you kindly for the articles and confirmation.

Accordingly to producer, only 5% solution of phenol and cyclohexanone can be used without harm to the freeze dryer and pump. t-buOH is ok.

I am late into this discussion but wanted to add some comments in case other people look at this thread of information.

Organic solvents may not only attack the acrylic components of a freeze dryer but may also attack seals and o-rings. It is always best to check with the original manufacturer of your equipment with your full list of solvents vs their components. In most cases the best components may be substituted for existing components but may still not offer 100% compatibility. This starts to become more obvious when a researcher has both organic and inorganic solvents and needs to make adjustments in the equipment components that are in opposition to one another. In such cases it is usually best to adjust the equipment for the organic solvents.

Cleaning after every freeze dry run is a must in solvent applications.

Most solvents have high vapor pressures. They will often either by-pass the condenser or will simply liquefy on the condenser. In such cases, without a liquid nitrogen trap, you are certainly going to have some amount of solvent going to the vacuum pump itself. Since high vapor pressure solvents are typically expelled during the first part of the freeze drying cycle you can run your vacuum pump with the gas ballast open during this period. The solvents will hit the very hot oil and then be expelled out of the pump. There are warnings that go with this not the least of which is -- do not use explosive solvents unless you take extreme measures and cautions (beyond this comment). Place non restrictive tubing on the outlet of the vacuum pump. The addition of a "P" trap is often necessary. Place the outlet of the tubing in an appropriate fume hood. As the solvents are expelled from the oil they will leave through the tubing on the outlet of the pump. Some of the solvents may condense in the tube itself and run back into the vacuum pump oil -- which is the reason for the P trap. Running a pump with the gas ballast open causes the pump to run hotter and will cause earlier denigration of the vacuum pump oil. It is best, during a run, to close the gas ballast when you believe the majority of the non water solvents are gone (as indicated by your pressure reading).

Monitor the quality of your vacuum pump oil frequently. As a reminder of what really good clean oil looks like you could put a small test tube with a fresh charge next to your vacuum pump site glass for referral.

Some researchers have opted to use dry pumps for heavy solvent applications. These pumps typically do not pull as strong a vacuum as the oil sealed pumps but have found a place in many labs.