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Encyclopedia > Rotary evaporator
A Büchi Rotavapor R-200 with a 'V' assembly (vertical water condenser). This modern style instrument features a digital heating bath and a motorised lifting jack. The evaporation flask has been detached in this illustration.

A rotary evaporator, or rotavap, is a device used in chemical and biochemical laboratories for the efficient and gentle evaporation of solvents. The main components of a rotary evaporator are a vacuum system, consisting of a vacuum pump and a controller, a rotating evaporation flask which can be heated in a heated fluid bath, and a condenser with a condensate collecting flask. The system works because lowering the pressure lowers the boiling point of liquids, including that of the solvent. This allows the solvent to be removed without excessive heating. Image File history File links Download high-resolution version (948x1401, 979 KB) Licensing I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ... Image File history File links Download high-resolution version (948x1401, 979 KB) Licensing I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ... A chemical substance is any material substance used in or obtained by a process in chemistry: A chemical compound is a substance consisting of two or more chemical elements that are chemically combined in fixed proportions. ... Biochemistry is the chemistry of life. ... This article or section is in need of attention from an expert on the subject. ... A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. ... Look up Vacuum in Wiktionary, the free dictionary. ... An electrically driven pump (electropump) for waterworks near the Hengsteysee, Germany. ... Look up condenser in Wiktionary, the free dictionary. ... The boiling point of a substance is the temperature at which it can change its state from a liquid to a gas throughout the bulk of the liquid at a given pressure. ...


Evaporation under vacuum can be performed in a standard distillation rig. However, the rotary evaporator has a key advantage. As the evaporating flask rotates, the liquids are forced to the outside of the flask with the centrifugal motion. This creates a larger surface area of the liquids and hence allows for quick, gentle evaporation. Laboratory distillation set-up using, without a fractionating column 1: Heat source 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed...


Rotary evaporators are highly effective at removing the majority of organic solvents during the extraction process. The remainder of the solvents are usually removed using a high-vacuum line. Rotary evaporators are usually not recommended for removing aqueous solvent due to water's high boiling point.


The key disadvantage with rotary evaporators is the potential for sudden uncontrolled boiling or "bumping" which can result in loss of some portion of the substance intended to be retained. Bumping can be prevented by regulating the strength of the vacuum, by reducing the temperature of the water bath, or by the use of boiling chips. Some rotary evaporators are also fitted with a 'descending condenser' glassware assembly that aids evaporations with bumping tendencies. Scientists who have many samples to evaporate often prefer to use a modern centrifugal evaporator which safely dries samples in parallel and also prevents "bumping" episodes. In an online forum, bumping is the act of posting in a thread simply to get it to the top of the first page so others may view it once more. ... Boiling chips are small, irregularly shaped stones used to prevent bumping of liquids during heating, boiling, or distillation. ... A centrifugal evaporator is a device used in chemical and biochemical laboratories for the efficient and gentle evaporation of solvents from many samples at the same time, and samples contained in microtitre plates. ...


The rotary evaporator was invented by Lyman C. Craig[1], while it was first commercialized by Swiss company Büchi. The Büchi Rotavapor continues to be the most widely used rotary evaporator, and Rotavapor has become a synonym for such instruments. Other manufacturers include IKA, Heidolph, Stuart and EYELA.


The most common form is the benchtop rotary evaporator, though large scale (20L and 50L) versions are available and are used by pilot plants in large pharmaceutical companies.


See also

In chemistry and physics, Vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. ... A centrifugal evaporator is a device used in chemical and biochemical laboratories for the efficient and gentle evaporation of solvents from many samples at the same time, and samples contained in microtitre plates. ...

References

  1. ^ Craig, L. C., Gregory, J. D., and Hausmann, W. Versatile laboratory concentration device. Anal. Chem. 22, 1462, (1950).

  Results from FactBites:
 
HAZARD ASSESSMENT FOR THE ROTARY EVAPORATION OF TOXIC SOLVENTS. (2148 words)
Thus, it is prudent that solvents be retained in the condensate collection flask during rotary evaporation and not vented into the air or condensed in the water aspirator and, in effect, poured down the drain (Huebner and Baer, 1992; van Leusen, 1994).
The pressure of methanol vapor escaping during rotary evaporation was obtained from manometer readings taken downstream from the evacuated system containing the evaporating solvent in thermal equilibrium with the heating bath.
The principle reason for solvent loss from the rotary evaporator is the inefficiency of the condenser, which cannot condense all of the solvent vapor because the vacuum line is attached directly to its jacket.
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