How to Use a Rotary Evaporator?

What is a Rotary Evaporator?

rotary evaporator (rotovap or rotatvap) refers to a kind of equipment for solvent evaporation under reduced pressure, which is composed of a vacuum system, a heated water or oil bath, a condenser and a motor that rotates the evaporation flask. They cooperate with each other and all play an essential role in the working process of a rotary evaporator. As its name suggests, what special is that the evaporation flask can rotate. It is an essential equipments for the processes of evaporation, concentration, crystallization, drying, separation, and solvent recovery in pharmaceutical, chemical and bio-pharmaceutical fields and other fields.

How to use a Rotary Evaporator?

Under vacuum conditions, constant temperature heating makes the rotating flask rotate at a constant speed, and the material forms a large-area film on the flask wall. The evaporation channel is highly efficient. The solvent vapor is cooled by a high-efficiency glass condenser and recovered in a receiving flask, which greatly improves the evaporation efficiency. It is especially suitable for the concentration and purification of biological products that are easily decomposed and denatured at high temperature.

rotary evaporator
rotary evaporator

Operation Procedures of Rotary Evaporator

  1. After turning on the vacuum pump, if it was found that the vacuum could not be hit, you should check whether each flask mouth is well sealed, whether the vacuum pump itself leaks, whether the sealing ring at the shaft is intact.
  2. Rotary evaporator has a continuous automatic feeding system, please pay attention when feeding: 1) Turn off the vacuum pump.  2) Stop heating. 3) After the evaporation stops, slowly open the tube cock to prevent backflow.
  3. Turn on the switch of the electric control box and adjust the knob to the best evaporation speed. Pay attention to avoid the vibration of the water bath and connect the cooling water.

General Rules of Rotary Evaporator

There are some rules you need to follow when you are using a rotary evaporator. You need to check:

①Whether each joint and interface are sealed tightly

②Whether the sealing ring and sealing surface are effective

③Whether the vacuum grease between the main shaft and the sealing ring is coated

④Whether the vacuum pump and its hose are leaking

⑤Whether the glass is cracked, chipped or damaged

rotary evaporator
rotary evaporator

Tips and Tricks of a Rotary Evaporator

  1. Glass pieces should be handled lightly, washed and dried.
  2. The heating tank should be filled with water and then electrified. Drying without water is not allowed.
  3. A small amount of vacuum grease should be applied evenly before installing the grinding instrument.
  4. The precious solution should be rehearsed firstly. After confirming that the instrument is suitable, it can be transferred to normal usage.
  5. The precise water temperature is directly measured with a thermometer.
  6. At the end of the work, turn off the switch and unplug the power plug.

Summary of Rotary Evaporator

The rotary evaporator system can be sealed and reduced into the pressure of 400-600 mm Hg. Use a heating bath to heat the solvent in the distillation flask, and the heating temperature can be close to the boiling point of the solvent. At the same time, it can also be rotated at a speed of 50-160 rpm to make the solvent form a thin film and increase the evaporation area. In addition, under the action of a high-efficiency cooler, the hot steam can be quickly liquefied to speed up the evaporation rate.


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