Rotary Evaporator Definition

Rotary Evaporator Definition

rotary evaporator definition

A rotary evaporator is a piece of laboratory apparatus that consists of a highs speed motor that spins the evaporation flask, a water bath, a condenser that is used to separate solvents from samples under low pressure, and a vacuum system. The two most common synonyms of this equipment are Rotavapor and Rotavap but it might have more.

The rotavap operates on the rotary process which entails reducing the solvent’s volume by distributing its thin film across the inner parts of a glass vessel at reduced pressure and elevated temperature. A combination of these conditions promotes most, if not the whole, of the excess solvent from the less volatile sample.

The design of a rotary evaporator is not etched in stone – there might be as many designs as there are stars in the Milky Way, but a typical design consists of four parts: solvent trap, condenser, heat bath, and rotor. Additionally, you will need to attach a vacuum pump or aspirator, plus a round-bottomed flask (which holds the sample that needs to be concentrated) and a bump trap that serves to prevent the solution from splashing or foaming.

Understanding More About Rotary Evaporator Definition

Let’s have a deeper look into each component

  1. Motor unit – rotates the vial or evaporation flask that contains your sample
  2. Vapor duct – serves as the axis of the rotation and also a vacuum-tight conveyor of the vapor that is being drawn from the sample.
  3. Condenser – a “cold finger” (special lab equipment that can be used to create a localized cold region) or a coil of a coolant in which the coolant mixture such as acetone or dry ice is placed
  4. Motorized or mechanical mechanism – quickly lifts the evaporating flask off the heating bath.
  5. Condensate-collecting flask – often placed at the bottom end of the flask and serves to catch a re-condensed distilling solvent.

>> Rotary Evaporator Parts and Their Functions

Special mention: Bath, Bump Trap, and Flask

It is recommended that you select a flask that can hold about two times the starting volume. The volume of your bump trap is a no big deal if you exercise proper caution, but is highly important in preventing you from recovering the “bumped” sample from the solvent trap and the condenser if bumping occurs. Most of the common lab solvents require a low-vacuum pump (which can be easily replaced by a sink aspirator) and temperatures within the range of 25°C and 50°C. The use of low temperatures comes with merits and demerits – the process is slower than if you used high temperatures but is less likely to undergo bumping.

>> Rotary Evaporation Technique


The possible danger lies in the usage of glassware that has flaws in its structure. The use of such glassware often causes implosions. Explosions can occur if you concentrate on unstable compounds that contain impurities, like rotavapping a seemingly uniform ethereal solution that contains peroxides.

Besides the hazards posed by the chemical solutions, mechanical parts of the apparatus may injure the user as well. Loose hair, necklaces, or clothes may get entangled in the rotating parts and result in burns and other injuries. The commotion created in such accidents can lead to more harm through spillage of the chemical solutions.

>> Plant Extraction By Using Rotary Evaporator