Rotary evaporators are a widely used tool in many laboratories—from chemical to biology laboratories. Also known as rotavaps, the primary purpose these useful instruments serve is to remove solvents from a mixture through the process of evaporation. While the goal of rotary evaporators is easy enough to understand, the process of how they work is a bit more complex. To learn the answer to the question of “How does a rotary evaporator work?” continue reading.

Pressure Is Reduced

To begin the process of rotary evaporation, a solvent is placed in a round-bottomed flask in the water bath of the rotary evaporator system. The system’s pressure is then reduced below atmospheric pressure through the use of a vacuum pump. Reducing the pressure in the rotary evaporator has numerous benefits. Namely, the reduced pressure allows the evaporation process to take place far more quickly.

In addition, the decrease in pressure will lower the boiling point of the solvent, which means the system will not need to implement high temperatures. This can cause sensitive solvents to oxidize and decompose. Plus, lowering the temperature of the system means that it will consume less energy during the process.

The Rotation Process Commences

After the pressure of the system is reduced, the flask containing the solution will rotate rapidly to further help facilitate the rotary evaporation process. Such rotation serves to increase the surface area of the solution which significantly increases its rate of evaporation. 

Heat Is Added

The rotary evaporator will then heat up the solution to speed up the process of evaporation even more. As previously stated, decreasing the pressure of the system significantly lowers the boiling point of the solution. As such, far less heat is needed to evaporate a solution using a rotary evaporator than a system that remains at atmospheric pressure. 

Condensation Occurs

As the solvent evaporates, its vapor will come into contact with a water condenser. There, the vapor will condense and drip into a receiving flask where it can be collected for disposal or reuse. As the solvent is removed from the solution, the concentrated compound will remain in the flask. Once the process is complete, the last traces of residual solvent in the sample should be completely eliminated.