Buchi Rotary Evaporators

Rotary Evaporators from the giant companies like Buchi or Across are typically used in removing the solvents from reaction mixtures and can accommodate volumes as large as 3 liters. As a matter of fact; the Buchi Rotary Evaporators or the Across International Rotary Evaporators are found in almost every organic laboratory, since they allow performing this task very quickly.

A closer look will reveal, a typical rotary evaporator has a water bath which can be heated in either a metal container or crystallization dish. This also helps the solvent from freezing during the evaporation process. The solvent that is removed under vacuum, gets trapped by a condenser and is collected for easy reuse or disposal.

In the lab, the house vacuum line, a circulation bath or a membrane pump, Polyscience Chillers are used as source for the vacuum. The vacuum is usually applied to the setup. This means, the boiling points of the solvents are significantly lower than at ambient pressure. The flask is rotated during the evaporation process. With this the surface area gets larger than normal which increases the evaporation rate significantly. The solvent is collected in a flask and can properly be ‘disposed off’ afterwards.

The main principle of the Across International Rotary Evaporators is that –

• Boiling points reduces on decreasing their pressure

• Allows solvents to be vaporized at a lower temperature

All these and much more are accomplished by a vacuum system composed of a Vacuum Pumps Online and a vacuum controller.

The condenser that is attached at the other end thus helps in converts the gas back to liquid, which requires lowered temperatures.

Within the Buchi Rotary Evaporators, the evaporation vessel constantly rotates. This however aims in increasing the surface area of the liquids. The centrifugal force thus keeps the liquid sticking to the inner surface of the vessel. It also helps in exposing a larger surface area thus causing faster evaporation.

Tips and Tricks of using the Across International Rotary Evaporators.

Distilled water should be used in the heating bath to minimize the scale build up.

The best protocol is a regular exchange of the water.

In the condenser has to be removed from the rotavap and the coil is soaked in a dilute nitric acid solution.