As you know, rotovap systems use vacuum to reduce the boiling temperature of the solvent. However, the use of vacuum increases the risk of implosion of glassware.
In this post, we take a look at the reasons why rotovap implosions occur, the dangers involved, and what you can do to prevent rotary evaporator glassware implosions and resulting injuries.
Why Rotary Evaporator Glassware Implodes and the Dangers
Of course, the desired effect of pulling vacuum on your rotovap setup is to reduce the pressure inside the system. However, the reduced pressure creates a suction effect on the inside of the system components. This can result in implosion of glassware.
Aside from ruining your samples, implosion can result in projectile glass fragments and the splashing of liquid. The risk of implosion is increased as you increase vacuum and decrease the pressure. The risk is exponentially increased when glassware is damaged.
How to Prevent Glassware Implosion and Minimize the Risk of Injury
Aside from wearing appropriate personal protective equipment, which should be a given in any lab environment, you should consider the following:
Use the Right Glassware
It’s important to make sure you only use glassware that has been designed for use under a vacuum. Other glassware may not be strong enough to withstand the pressure change.
Many rotovaps come with the option of safety-coated glassware which helps protect against shattering. Although, bear in mind that this mainly applies to condensers and collection flasks. Evaporation flasks are typically not safety-coated because they need to withstand high bath temperatures which could degrade the plastisol coating.
For example, the FAQ section of the Hei-VAP Precision rotary evaporator explains which components are coated and why. For this product, when you opt for a coated glassware set, only the condenser and collection flask will be coated.
Check Your Glassware Carefully
All glassware should be inspected carefully before use with a rotovap and should not be used if it’s visibly damaged. Aside from cracks, look out for any scratches or chips. Note that it only takes a tiny crack to compromise the integrity of the glassware and cause it to implode once under vacuum.
If your glassware doesn’t have a safety coating, to minimize the damage potential if the glassware does implode, you could use tape. Filament tape applied in a crisscross pattern will help pieces stay together in case of an implosion or explosion, meaning there’s less chance of glass shards injuring lab personnel and damaging nearby equipment. Mesh or netting is often applied for a similar effect.
This rotovap setup includes a taped collection flask.
Increase the Vacuum Slowly
Aside from potentially causing your sample to bump or foam, applying too strong of a vacuum too quickly could increase the risk of implosion. Ideally, you should increase it gradually and only to the level necessary for your application.
Use a Fume Hood
If you’re worried about implosion, you might consider using the rotovap under a fume hood. This may be necessary anyway for certain applications to avoid inhalation of noxious fumes.
If your main reason for using a fume hood is implosion (or explosion) risk, then you’ll likely need to close the sash and keep it closed at all times. However this makes it difficult to operate and control the rotovap equipment. Thankfully, with some units, you can detach the control panel and operate the unit from outside of the closed hood.
An alternative to using a fume hood is an enclosure like the Heidolph unit below.
Also, some large-scale rotovap systems come with built-in enclosures that help protect against shattered glassware and splashes.