You may be used to seeing rotary evaporators out in the open on the lab benchtop or tucked away in a fume hood. Both options are acceptable, but will depend on various factors of the application and the environment.
In this post, we explain the considerations involved when deciding whether or not to use a fume hood with your rotary evaporator.
1. Health Risks Due to Fumes
A rotary evaporator is used to remove volatile solvents. Although a rotovap is designed such that evaporated solvents are condensed and collected, it’s possible that some volatiles could still escape. If present in high enough concentrations, certain vapors could pose risks of respiratory illness or explosion.
As such, evaporative processes should always be carried out in a well-ventilated area. If ventilation is inadequate, then you’d best get the equipment under the hood.
Some processes will involve the use of solvents that generate noxious vapors, and in this case a fume hood should be used, no matter how well-ventilated the area is.
2. Risk of Explosion
Certain applications come with an increased risk of explosion, including when using chemicals or mixtures that are explosive under certain conditions. For example, there have been multiple reports of azide in the presence of halogenated solvents causing an explosion that shatters rotovap glassware.
When an explosion occurs, the rotovap operator and other bystanders are at risk of being hit by projectile glass shards and dangerous chemicals. Lesions from glass and chemical burns are common injuries associated with various lab explosions.
To reduce the risk of injury, you can use the rotary evaporator in a fume hood with the sash lowered. After one serious incident involving exploding rotovap equipment, lowering the fume hood sash was one of the preventative recommendations made. In this case, a researcher was using a rotovap to remove organic solvents from an azobenzene precipitate. The rotating flask exploded and sent glass fragments towards her face, resulting in the need for stitches.
3. Risk of Implosion
There is also the risk of implosion, and this is most likely to occur if your glassware has a crack or fracture in it before use. Once under the pressure of a vacuum, the defective glassware is prone to break easily, resulting in the risk of injury. You can use coated glassware to help reduce the risk of the rotovap glass breaking, but a fume hood can help too.
If you’re choosing to use a fume hood because of explosion or implosion risk, then ideally, you’ll want to keep the sash completely closed at all times. Some models come with a detachable control panel that can be used to operate the unit from outside a closed hood. For example, many Heidolph benchtop rotary evaporators come with this feature.
The Hei-VAP Advantage and Hei-VAP Precision both come with detachable control panels.
4. Safety Concerns With High-Temperature Applications
Your application may involve safety risks other than those mentioned above. Say, for example, you’re performing a high-temperature evaporation that requires the use of an oil bath heated above 100°C. This setup can pose a safety concern when left running on a bench unattended.
By setting up the equipment under a fume hood, it will be out of the way and less likely to be disturbed and pose a risk of injury.
4. Having the Right Equipment
This may sound obvious, but if your setup won’t fit under the fume hood, then you won’t be able to use it. Condensers usually come in two different types: vertical and diagonal. The former is usually better for a setup where you have limited bench space to work with, while the latter is more suited to setup where there is limited height availability. If you have a low fume hood that won’t fit your vertical condenser, then you may be out of luck.
A LabTech EV311 Advanced Rotary Evaporator with a vertical and diagonal condenser.
That being said, safety is of utmost importance, so if you’ve deemed from the other criteria above that you need to use a fume hood, then you should make sure you have the right equipment to do so.
Alternatives to Using a Fume Hood
In many cases, a fume hood simply isn’t an option, whether you don’t have one in the lab, or you have one but it’s being used for other applications. So what if you absolutely need more ventilation or better protection than your current setup offers? Well, there are a couple of options:
Purchase an Enclosure
An enclosure can be an ideal alternative to a built-in fume hood and will minimize exposure to fumes and vapors.
For example, the Heidolph enclosure pictured above was created in partnership with AirClean® Systems and offers a user-friendly alternative to a fume hood.
Some large-scale rotovap systems will have their own enclosure built into the unit. However, the examples below only provide protection against shattered glassware and splashes, and do not provide ventilation.
The Hei-VAP Industrial B Rotary Evaporator and the Hei-VAP Industrial Safety Rotary Evaporator incorporate a safety enclosure.
Build a Suitable Environment
Depending on what your application calls for, you may need to operate in a special environment. For example, some applications should be carried out in a laboratory that is fully explosion-proofed and meets minimum ventilation requirements.
In addition to the environment itself, it’s important to consider any additional equipment required such as personal protection equipment (PPE).
Conclusion
The main reasons for using a fume hood with a rotovap setup are to minimize the risks associated with the inhalation of fumes produced and to protect from injury in cases of exploding or imploding glassware. If these are concerns for your application, then using a fume hood should be strongly considered. Alternative options include purchasing a purpose-built rotovap enclosure or carrying out your process in a special environment.
