Rotary evaporators are common laboratory instruments, found in virtually every organic laboratory, and are used to remove or isolate components of reaction mixtures based on differences in their boiling points. This is often done after a separation or extraction process. During rotary evaporation, the solvent is removed under vacuum and then trapped by the condenser and collected for reuse or disposal.

Most rotary evaporators have 4 components:

1. Heating bath

2. Rotary drive

3. Condenser

4. Solvent collection flask

Set-up:

1. Select a flask that accommodates roughly twice the starting volume.

2. Select a bump trap to reduce the likelihood of sample loss with bumping or violent boiling. Better yet, consider using a vacuum pump system.

3. Select and attach a vacuum pump capable of reaching your desired vacuum level and that is compatible with your specific solvent vapors.

4. Select the proper temperature for your water bath— lower temperatures make for a slower process but reduce the likelihood of bumping or damage to your sample due to overheating.

Commencing a rotary evaporation:

1. Turn on the chiller and allow the temperature to reach set point.

2. Turn on the water bath. Allow bath to reach set point prior to beginning evaporation.

3. Secure your evaporation flask with Keck clamps. Unless you are very confident, don’t rely on the vacuum to hold your flask.

4. Begin flask rotation. It should spin fast enough to create an even coating on the inner surface of the flask.

5. Turn on the vacuum pump, close the stopcock on the condenser, and allow the sample to spin under vacuum for approximately 1 minute. The sample will likely start to boil—if the sample begins to bump or boil violently, vent the system and adjust the vacuum set point.

6. Once boiling has ceased, and solvent is collecting in the solvent trap, lower the flask about halfway into the heating bath.

7. The process is best controlled by adjusting the vacuum, due to the pump’s ability to respond quickly and accurately.

Halting a rotary evaporation:

1. Raise the flask from the heating bath.

2. Open the stopcock on the condenser to vent the system to the atmosphere.

3. Turn off rotation.

4. Turn off the vacuum supply.

5. Remove the evaporation flask; remove and empty the solvent collection flask.

6. Turn off water bath and chiller (unless you are starting a new evaporation).