How To Use A Rotary Evaporator

You've probably heard of it, but what exactly is a rotary evaporator and how would you go about using one? A rotary evaporator is considered a standard piece of equipment in most laboratories nowadays and the fastest and most environmentally friendly way of removing a volatile solvent. 

What Is A Rotary Evaporator or “Rotovap”?

A rotary evaporator or “rotovap” works by increasing the rate of evaporation of a solvent by reducing its pressure which ultimately ends up lowering the boiling point of the solvent. Then the sample is rotated to increase the effective surface area coverage while heating the solution. 

How To Use A Rotovap

Let us walk through how to use a rotary evaporator: 

Firstly, let's turn the power on, adjust the position of the glass apparatus using the lift knob control to make sure that you have enough room between your instrument and the water bath. Then you should check the temperature of the water bath and at this point if additional water is needed make sure to add water into the bath accordingly while continually checking the temperature.  Make sure that if you DO need to add water to the water bath, that you use distilled water since it is free of particulates and will keep your rotary evaporator continually working in pristine condition!

Locate the receiving flask and make sure to check it for any leftover waste solvent, if you find that there is any liquid in there, remove it and dispose of it accordingly. Afterwards, make sure to clean out the receiving flask with a small amount of acetone. Now that your receiving flask is sterile, you can turn on the cooling water to the condenser coils and the vacuum to make sure that the vent holes are aligned.

Finally, you can add your sample solution to the round bottom flask, but make sure not to fill it over the halfway point! Connect your evaporation flask (round bottom flask) to the ground glass joint on your rotary evaporator. Then start rotating your flask. 

You have some play now that your machine is up and running. First, you want to make sure to monitor your venting process and adjust the pressure accordingly making sure that your solvent is bubbling and then letting it stop, repeating this until it settles. Your flask should be cool at this point.

Once you’ve gotten your solution to this point, use the regulating valve (stopcock) to generate a vacuum and carefully lower your evaporation flask until the lower part of the flask is submerged in the water bath. If your solution begins to boil aggressively make sure to use the stopcock valve to release the vacuum pressure. Once everything is stable you can leave the solution to evaporate. 

Rotary evaporators allow you to adjust the rate of evaporation, so if your evaporation rate is too slow, turn your heat back on to the thermostatic water bath and adjust accordingly. Once completed make sure to carefully remove your evaporation flask and your solution should be set!

Rotary Evaporator Safety

There are lots of different variations and models of rotary evaporators, but the process and concepts are essentially the same. Make sure to use extreme caution and safety when using a rotary evaporator and make sure to use protective safety equipment. If you have never used a rotary evaporator before make sure to have a trained professional walk you through the process as you will/could be working with dangerous solvents that could potentially cause harm to yourself or others.

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