Rotary evaporators have for decades been staples in labs and industries performing chemistry, including labs in the chemical, environmental, materials, life science and forensics industries. Key applications include sample concentration, solvent recycling, extractions, and separation of solvent mixtures.
In their simplest embodiment, “rotovaps” consist of a temperature bath, rotating flask, condenser, collection flask, and vacuum source. Solvent distills from the sample under the combined effects of heat and vacuum, and collects after condensation in the collector. Recovered single-phase organic solvents may be dried and re-used; binary, tertiary, or quaternary solvent mixtures are also re-used but may need adjustment for composition.
Water is the fluid of choice for the bath, but some laboratories use oils to reach heating temperatures of up to 180°C. Several choices are available for the condenser coolant. Until about 10 years ago, almost everyone used house water. Concerns over water consumption caused many labs to switch to a chiller to recirculate coolant into and out of the condenser coils. Chillers provide more precise cooling, greater control over condensation, a greatly reduced environmental footprint, and are overall less expensive to use than water. High-efficiency trapping of low-boiling solvents is achieved with a “cold finger” charged with dry ice and acetone.
An important new concept in laboratory rotary evaporation is systems integration. This means the main components of the evaporation solution are fully integrated with respect to parameters and control.
The rotary evaporator components our readers use in their labs include:
|Dry ice condenser||5%|
|Cold finger condenser||6%|
Rotovaps can also be used for flavor extraction in the food industry and HPLC and natural product sample prep. The fields of work our respondents’ labs most closely align with are:
|Biochemistry and biology||13%|
|Food and beverages||8%|
Other applications rotary evaporators are used for include drying down powders using a test tube adapter and trapping hazardous waste liquid. Here are the most common applications our respondents are using their rotovaps for:
|Distilling of low-boiling solvents||20%|
|Distilling of temperature-sensitive substances under vacuum||10%|
|Recycling of solvent waste||7%|
|Concentration of substances||29%|
|Drying of powders||6%|
|Separation of material mixtures||6%|
|Chemical synthesis under reflux||5%|
Newer rotovaps may incorporate thermocouple-controlled operation, in which a pump integrates with a controller and a thermocouple located in the vicinity of the condenser coils. As the coil temperature rises through heat transfer between the condenser and the evaporated solvent, the vacuum is bled out through valving to maintain steady distillation. Another technique, known as “RPM” control, speeds or slows the pump’s inner workings to control the delivered vacuum.
Purchasers should consider several vacuum and condenser cooling options before buying a rotovap: Cooling method should be decided based on the expected solvent load and buyers should also consider whether automated, volume-dependent rotary evaporation is desired.
Here are the factors our respondents found most important in their buying decision:
|Important||Not Important||Don't Know|
|Built-in vacuum controller||47%||31%||21%|
|Clockwise and counterclockwise rotation of the distilling flask||22%||51%||28%|
|Ease of installation||74%||13%||13%|
|Ease of use||79%||8%||13%|
|Low maintenance/easy to clean||84%||1%||14%|
|Low operating cost of ownership||78%||7%||14%|
|Motorized lift systems||26%||54%||20%|
|Quiet drive motor||47%||36%||17%|
|Service and support||69%||13%||19%|
For more information on rotary evaporators, visit www.labmanager.com/evaporators