How does a Rotary Evaporator Work?

As a common evaporator in laboratory and industry, a rotary evaporator has been widely recognized for its excellent distillation and extraction performance. Generally, it is used to remove a volatile solvent from a liquid mixture. A rotary evaporator is mainly composed of following parts: a vacuum pump, a chiller, a condenser pump, a rotating flask and a receiving flask and other components. Most of people may be interested in how a rotary evaporator works. Hence, the working principle and process of a rotary evaporator will be introduced specifically in the following.

450Rotary Evaporator

How does a Rotary Evaporator Work?

A rotary evaporator (rotovap or rotavap) evaporates solvents from samples by utilizing the principle that the solvent will have a lower boiling point at a reduced pressure. Specifically speaking, the stepless speed regulation is adopted to make the evaporation flask rotate at a constant speed. By the rotation, materials can form a large area of uniform thin film on the inner wall of the flask. The evaporation flask is heated evenly by a water or oil bath, and materials with a lower boiling point is evaporated rapidly under the vacuum condition. The solvent steam is recycled in the receiving flask after being cooled by the high efficiency glass condenser.

Rotary Evaporator

Working Process of a Rotary Evaporator

  1. Preparations

a. Pour the mixture of solvent and required compound in a round-bottom flask, which should be fiiled less than half full of the solution.

b. Fill the rotovap cold traps with dry ice.

c. Attach a glass “bump trap” to prevent any solution from entering the main part of the rotovap. Secure with a clip.

d. Connect the flask and bump trap to the adaptation part with a clip.

e. Lower the flask into the water bath, preventing the flask from disconnection.

  2. Operation

The working process of a rotary evaporator is a consecutive process under the reduced environment. There are several steps for the operation:

a. Under reduced pressure, the evaporation flask was continuously rotated while the solvent was being distilled. The evaporation flask is a pear-shaped or round-bottomed flask with a standard ground mouth connection. It is connected with the pressure reduction pump through a serpentine condenser.

b. After substances get evaporated by heating, the gas-phase substances will go into condensing part to get condensed. In this step, gas substances are transferred through the glass tubes.

c. After gas-phase substances got condensed into liquid-phase, the liquid-phase substances will be transferred into receiving flask, which is the final destination of extracted substances. And then users will take the receiving flask out of rotary evaporator equipment.

During the whole working process, there is always a vacuum pump providing a vacuum environment for the rotary evaporator, which guarantees the whole system work in a reduced environment and the automatic feeding system formed by the pressure difference between atmosphere pressure and vacuum pressure.

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