Rotovapping Aqueous Solutions - Need a cold trap? I am working on a large scale natural product Rotovapping project. There are two botanical extracts to evolve, combined in processing. The solvents are 50% EtOH and 50% glycerin. There is a large volume of material to dry that will require several weeks of run time. I am using a diaphragm pump that has specs for chemical resistance; I am not too concerned for any issue with EtOH. My concern is that the efficiency of the pump may be impacted by water vapors if I push the parameters to expedite the process. I know that cold traps are encouraged for high volatiles...but would it be helpful to add one to condense any water vapor also, for a run this large? The pump does not have any trap system in place currently. Not sure if it is worth the trouble to create an inline trap as or if it will enhance the speed.
You will always want a cold trap not only to protect the pump but also to make sure it's running at peak efficiency at all times. Especially when you push the vacuum and heating to try to expedite the process, you never know when the whole thing might suddenly bubble up. A clean cold trap will also allow you to recover the material that has escaped the main chamber, whereas without one you'd probably be faced with loss of compound and having to repair the pump.