Rotary Evaporation Technique

A rotary evaporator is extremely instrumental in chemical laboratories due to its potency in the extraction of solvents through evaporation. This has made it be widely used in the extraction of elements and preparation of distillates. Well, the rotary evaporation technique is often well understood by narrowing down to its practicability.

This involves the parts and functions of rotovaps in the lab. The rotary evaporator is made up of a vacuum system that is responsible for the reduction of pressure during the extraction process. A motor unit ensures the sample is revolved. It also incorporates a heated bath and a condenser to gather the distillate. These are some of the basic features but digitalized motor-lift rotavap can contain additional features.

rotary evaporation technique

Rotary Evaporation Technique

Ideally, the rotary evaporation technique relies on the reduction of the solvent in the interior vessel to form a thin film after it is exposed to low pressure and high temperatures. This makes it simple to draw excess solvents from those samples that are less volatile. The main components that come into play in this technique are the solvent trap, condenser, rotor, and heat bath.

Ensure the Heat Bath At Proper Temperatures

To get started, the basic consideration is to ensure the heat bath is at proper temperatures while the condenser is cold enough to ensure the optimal success rate of the entire process. If you are in a lab and possibly another user had used the apparatus it is important to do some crosschecks like ensuring the solvent trap is an emptied because some unknown solvents can yield suboptimal results.

Afterward, the flask and bump trap is tightly secured on a clamp before the rotor is activated. The speed at which the rotor rotated is very crucial in the formation of a thin film of the solvent in the flask. This is made possible through the force exerted.

Activate the Vacuum Pump

The vacuum pump is then activated but with a precaution that the condenser is made airtight until there is no whistling. The sample is subjected to these conditions until the sample begins to boil which is typically after a minute or so. Some people might mistake it with pumping but there is no need to worry so long as the bubbles don’t come in touch with the neck of the vessel because it can be dangerous because of the increased pressure levels. If it happens the pressure is reduced by opening the cork.

Remove the Solvents

Once the boiling subsides, the flask is lowered to halfway into the heat bath to prevent condensation from occurring on the outer surface of the flask. The process is closely monitored until all the solvent has been removed after which the vacuum and the rotor are switched off before removal of the flask. If there are more solvents to be extracted the procedure can be repeated but it is advisable to ensure that the flask is empty.

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The success of this technique mostly depends on adherence and following the procedure keenly. Additionally, different reagents ought to be handled based on its specific considerations. For instance, a liquid nitrogen trap can be attached before the solvent is passed through the vacuum especially when it comes to the handling of corrosive substances. A reactive solvent like water and Thionyl chloride should be avoided or try other alternatives.

Some advanced techniques like cracking the vacuum can be used when it comes to rotary evaporation of substances like toluene and ether.