When purchasing a rotary evaporator, you may wonder whether you should include a vacuum source or not. We strongly recommend doing this as a controllable vacuum source allows for using the rotovap in a faster, more controlled, and safer manner.
Depending on the model a rotovap may have a built-in vacuum control and only a vacuum pump needs to be added. If this is not the case, however, you will probably need both a vacuum pump and a manual or digital vacuum controller. A controller can significantly increase your cost, check out this blog for advice on minimizing this.
Heidolph manual and Buchi digital vacuum controllers
Having a controllable vacuum source allows for precise adjustments in pressure to obtain the desired evaporation rate. This allows you to increase evaporation rate without increasing the temperature of your bath, and in many instances increases the evaporation rate beyond what is achievable with the bath alone. A controlled and even evaporation rate also means a much smoother evaporation, resulting in better solvent-product separation and a decreased chance of bumping. Furthermore, using only heat to evaporate your solvent may mean risking reaction of temperature-sensitive compounds in your mixture. Decreasing the boiling point through vacuum mitigates or eliminates that risk.
Reduced pressure also decreases the boiling point of your solvent and makes removing high boiling solvents faster and safer. This means you can work at lower bath temperatures and, in many cases, use water in your heating bath in situations where oil would otherwise be necessary. This is easier and safer as oil baths leave a residue on your evaporation flask and, when hot, can be fire hazards in the presence of flammable gas vapors.
Adding a vacuum source to your rotovap will make it easier and safer to use, improve sample separation, and help preserve your sample.
