Why Does the Rotary Evaporator Bumping?

Rotary evaporator, also known as rotary evaporation machine, is a commonly used equipment in laboratories. It consists of a motor, distillation flask, heating pot, condenser and other parts, which is mainly used for continuous distillation of volatile solvents under reduced pressure. Rotary evaporators are mainly used for concentration, crystallization, drying, separation and solvent recovery in the pharmaceutical, chemical and bio-pharmaceutical industries.
 
The principle of rotary evaporator is as follows. Under vacuum conditions, constant temperature heating makes the rotating bottle rotate at a constant speed, and the material forms a large-area film on the bottle wall, which evaporates efficiently. The solvent is evaporated and is cooled by a high-efficiency glass condenser, then is recovered in the collection bottle, which greatly improves the evaporation efficiency. Rotary evaporator is especially suitable for the concentration and purification of biological products that are easily decomposed and denatured at high temperature.
 
Rotary evaporator is a commonly used evaporation purification instrument in the laboratory. Then, why does the rotary evaporator bumping during use?
 
The usual reasons for the bumping of rotary evaporator are as follows:
1. Solids are deposited during operation.
2. The rotating speed of the rotary evaporating flask is too high.
3. The temperature of the bath is too high, for example, the temperature of ethanol generally does not exceed 35°C.
4. The round-bottomed flask is immersed in the water bath too deeply, and the temperature is high and the speed is fast, which easily causes bumping.
 
Commonly-used solutions when bumping occurs in a rotary evaporator:
1. It can reduce negative pressure distillation, and even use atmospheric distillation.
2. Lower the distillation temperature appropriately.
3. Adjust the speed according to the specific situation.
4. Distill several times and use a small amount.
 
In addition to the above four solutions, there is another one. That is, the operator should be watching the experiment next to the rotary evaporator. If bumping occurs, immediately deflate and reduce the negative pressure slightly.