Choosing a Laboratory Rotary Evaporator


Understanding the basics of Rotary Evaporators before buying them

Rotary evaporation is the process of reducing the volume of a solvent by distributing it as a thin film across the interior of a vessel at elevated temperature and reduced pressure which promotes the quick removal of excess solvent from less volatile samples. Rotary Evaporators are used in chemical laboratories. This instrument uses evaporation to gently and efficiently remove the solvents from samples including many organic, inorganic, and polymeric materials. A simple rotary evaporator system was invented in 1950 by the chemist Lyman C. Craig. It was first commercialized by the Swiss company Büchi in 1957.

How a Rotary Evaporator works?

The main components of a rotary evaporator or “rotovap” include a motor unit, a vapor duct, a vacuum system, a heated fluid bath, a condenser with either a coil passing coolant, or a “cold finger, a condensate-collecting flask and a mechanical or motorized mechanism. In a rotary evaporator, the motor rotates the evaporation flask or vial containing the user’s sample. Vapor duct is the axis for sample rotation, and is a vacuum-tight conduit for the vapor being drawn off the sample. The vacuum system substantially reduces the pressure within the evaporator system. The vacuum system can be as simple as a water aspirator with a trap immersed in a cold bath (for non-toxic solvents), or as complex as a regulated mechanical vacuum pump with refrigerated trap. A heated fluid bath, which is usually water, heats the sample. The condenser used in rotary evaporator can be simple or complex, depending upon the goals of the evaporation, and any propensities the dissolved compounds might give to the mixture. The condensate-collecting flask is located at the bottom of the condenser and it catches the distilling solvent after it re-condenses. The mechanical or motorized mechanism quickly lifts the evaporation flask from the heating bath.

Considerations before buying a Rotary Evaporator

Rotation speed range (rpm), vacuum (mm Hg), temperature, pressure (mbar) and condenser are key parts that should be considered when buying a Rotary Evaporator. You can decide on the type of Rotary Evaporator suitable for your application based on the size, type and sensitivity of the samples. For example, if the samples are acids, they require an acid-resistant system.

Safety precautions

Safety is an important component of every laboratory operation and procedure. Although evaporation is a simple operation, there are hazards associated with it including implosions resulting from use of glassware that contains flaws, such as star-cracks, explosions that may occur from concentrating unstable impurities during evaporation or explosion due to taking certain unstable compounds, such as organic asides and acetylides, nitro-containing compounds, molecules with strain energy, etc. to dryness.

It is recommended to take precautions to avoid contact with rotating parts, particularly entanglement of loose clothing, hair, or necklaces. In such cases, a rotating mechanism can draw the user into the apparatus. In an incident like this, a user is subject to burns, sharps and chemical exposure. Extra caution must also be applied to operations with air reactive materials, especially when under vacuum. A leak can draw air into the apparatus and a violent reaction can take place.


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