Tips and Tricks to Avoid Rotary Evaporator Glassware Implosions

When using your rotary evaporator, you are at a constant risk of glassware implosion. In this blog post, we’ll go over the different reasons why glassware implosions occur, the different dangers that are involved, and the different mitigative measures that you can undertake to prevent or reduce the risk of glassware implosions.

Why does rotary evaporator glassware implode?

Using vacuum with your rotary evaporator comes with a significant set of advantages, but if we were to list the disadvantages, one stands out: Glassware implosion. Besides throwing your samples down the drain, all over the wall, and all over you (Wear your PPE), implosions can result in projectiles of glass shards. The risk of implosion is directly proportional to the increase in vacuum: the higher the vacuum, the higher the chance of your glassware turning into a gnarly lab accident. The risk is exponentially increased when glassware is damaged. 


How to prevent glassware implosion


1-Checking Your Glassware for Cracks and Signs of Wear: 

You should routinely inspect your glassware for damage before every rotary evaporator run, and you shouldn’t use it if it’s visibly damaged. Look for cracks, chips, and scratches.  If your glassware isn’t safety coated you could always use filament tape in a crisscross pattern, which will help keep the different pieces of glass together in case of both implosions and explosions. Mesh or netting can also be applied for a similar effect.


2-Choosing the Right Glassware:

When choosing glassware, you should make sure that it is designed to withstand vacuum. And while certain rotary evaporators come with the option of safety-coated glassware, it’s always better to stay on the safe side, and double check the specs yourself. You should also bear in mind that evaporation flasks aren’t usually safety coated given the high bath temperatures that they need to withstand that could degrade the plastisol coating.


3-Using a Fume Hood:

While certain applications force you to run your rotary evaporator under a fume hood, you might want to consider that option to mitigate the risks presented by imploding glassware. You’ll want to keep the sash closed at all times, which will make it difficult to control and operate your rotary evaporator.


4-Increase the Vacuum Slowly:

An incremental increase in vacuum during your operation comes with a solid set of advantages, like decreasing the risk of bumping and foam formation, and a decreased risk of glassware implosion.

Tips and Tricks to Speed Up your Rotary Evaporation Process

In rotary evaporation, as in a lot of other things happening in your lab, time is of the essence. Maybe you need those APIs purified ASAP, or maybe your clients needed that ethanol removed from the cannabis they sent you yesterday. Bottom line is a rotary evaporator can only spin so fast, but we got your back. In today’s blog post we’ll give you a few tips and tricks to speed up your rotary evaporation process.


Increase your Vessel Size

It might  sound counterintuitive to use a vessel that is considerably larger than your sample size. However, increasing your vessel size is the way to go if you’re aiming for a more efficient process. A larger vessel means an increased surface area, which means that a bigger portion of your flask will be in contact with the water in the water bath, which paves the way for a quicker and more even heating process. At the same time, using a large vessel also means that the sample inside of the flask is exposed to more air, making evaporation more efficient!


Increase your Vacuum Level

As discussed in one of our previous blog posts, using a controllable vacuum source gives you the luxury of adjusting the pressure with surgical pressure, thus providing you with your desired evaporation rate. Variating the pressure (increasing it to be more specific), will decrease the pressure, and thus make your process faster. And while this is generally true, you need to avoid a few pitfalls, like bumping and foaming. A sharp decrease in pressure can also lead to a hasty evaporation, not allowing the solvent to evaporate properly. The uncondensed vapor might end up inside of the vacuum pump, which is undesirable to say the least. Oh, and did we mention that sharp drops of pressure in your flask might make it implode?


Increase your Bath Temperature

This one’s pretty straightforward: a higher bath temperature means a higher rate of evaporation, and a more efficient process. Just make sure that your sample can handle an increased temperature without any side reactions occurring, do your best to avoid bumping, and follow the rule of 20 to avoid too much solvent vapor formation.


Increase your Rotation Speed

Last but not least, increasing the rotation speed of your evaporation flask. To better understand how this works, we need to take a closer look at the two main functions achieved by rotating the flask: It improves the heat transfer from the water bath to the solvent and the flask, and it increases the evaporation rate by increasing the surface area of the liquid inside of the flask. However, reaching too high of a speed can lead to the sample being pressed against the sides of the flask, thus greatly reducing the efficiency of the process. You want to aim for 250-280 rpm to reach optimal turbulence.

How to Prevent Foam Formation and Bumping in your Rotary Evaporator

It is a common occurrence for samples being evaporated in a rotary evaporator to foam up, or starting bumping. This usually leads to sample loss, and possibly contamination. Foaming occurs when the sample’s surface tension decreases, leading to the production of bubbles. Bumping however refers to the sudden and vigorous release of vapor bubbles from the liquid phase, which can result in the sample splattering or even ejecting from the evaporator flask. Both situations can be problematic as they may lead to sample loss, reduced efficiency, or potential hazards. In this blog post, we’ll discuss a few steps you can take to mitigate the risk of foaming and bumping.


Reduce your sample’s concentration:

Foaming can occur if your sample is too concentrated. Diluting it with an appropriate solvent can help reduce foaming tendencies.


Adjust the vacuum pressure:

Lowering the vacuum pressure can significantly decrease the risk of bumping. You’ll want to ensure that the vacuum level is set correctly based on the sample’s boiling point to maintain a controlled evaporation process. As a rule of thumb, you’ll want to go slow by starting with  little vacuum, and gradually decreasing the pressure while visually inspecting your sample to make sure no bumping occurs.


Use an appropriate flask size:

Make sure that the flask size you’re using can comfortably fit your sample. This will prevent both foaming and bumping. You want to avoid overfilling your flask.


Use anti-bumping agents:

Glass beads and boiling chips can provide your sample with a nucleation site for bubble formation which ultimately reduces the risk of bumping.


Control the heating rate:

Just like the vacuum pressure, you want to keep a tight control of the heating rate of your sample. Gradually increase the temperature to avoid the  formation of large bubbles. A slower, more controlled heating process promotes gentle evaporation.


Optimize solvent selection:

Different  solvents have varying tendencies to foam or bump. Selecting a solvent with lower foaming characteristics or employing an appropriate solvent mixture can mitigate these issues.


Use Personal Protective Equipment (PPE):

As always, safety first! Even if you follow all the aforementioned steps, surprises still happen. Make sure to don your lab coat, gloves, and safety goggles to protect yourself in case of splattering or sample ejection.


There you have it! Next time you use your rotary evaporator, make sure to follow these steps for a foaming-free bumping-free process. Stay tuned for more!

Dry Ice: The Phantom Menace

Years after “Star Wars: Episode 1 – The Phantom Menace ” was released, George Lucas revealed that the title was a reference to Palpatine concealing his identity as an evil Sith Lord behind the façade of a good-willing public servant. And while dry ice slurries aren’t nearly as evil as Sith Lords, they do pack a few “evil” disadvantages that we’ll discuss in today’s blog post (keep reading all the way for a little surprise at the end of the blog).

Rotary evaporators are widely used in chemical and biological laboratories for distillation, solvent removal, and concentration of samples. One of the techniques employed in rotary evaporation is the use of dry ice slurries to maintain low temperature during the process. However, this seemingly routine procedure can pose serious safety hazards if not handled correctly.

A director at BMS recently noted the safety concerns that arise from the use of dry ice. As experienced scientists, we understand the potential risks of exploding condensers when water builds up in the cold finger and is not emptied and/or mistaken for acetone. The resulting rapid expansion of the slurry can lead to shattered condensers, posing the risk of physical injury to the scientists.

Exploding condensers are a significant issue that is not adequately addressed particularly in university Labs. Injuries can range from Minor cuts to serious lacerations that require medical attention. According to a report published by the Centers for Disease Control and Prevention (CDC), from 2001 to 2018 there were 2578 reported lab associated injuries involving rotary evaporators with 20% of these injuries resulting from shattered glassware.

The report also revealed that rotary evaporators were the second most common equipment involved in lab-associated injuries, after pipettes. The most common type of Injuries associated with rotary evaporators were cuts, punctures, and abrasions, with the hand being the most frequently affected body part. In addition to physical injuries, exploding condensers can also lead to equipment damage and downtime, negatively impacting productivity, research progress, and causing delays. Replacing damaged or broken equipment is often costly, and the unavailability of spares can further exacerbate the situation.

To mitigate these risks, it is crucial to ensure that proper training and education are provided to scientists who use rotary evaporators. This includes educating lab personnel on the correct use of the dry ice/acetone slurries, the importance of monitoring for water build-up in the cold finger, and appropriate disposal of the mixture after use. The use of protective gear such as gloves and eye protection should be mandatory to minimize the risk of physical injury.

Expanding on the negative impact of damaged or broken equipment due to exploding condensers, it is essential to highlight the financial cost that can be incurred. Replacing a damaged or broken condenser can be an expensive affair, and in many cases, there may not be any spares readily available in the lab. This can result in a significant delay in replacing the broken part, which can negatively impact productivity and research progress. Even if the replacement part is ordered immediately, it may take several days or weeks to arrive, which can be a major setback for ongoing experiments.

Lab guidelines and procedures should be established to ensure that all laboratory personnel are aware of the risks associated with dry ice/acetone slurries and the necessary precautions to prevent accidents and injuries. Spare parts should be readily available to facilitate the timely replacement of damaged or broken equipment.


In the style of master Yoda:

Widely used in chemical and biological labs, rotary evaporators are, hmmm. For distillation, solvent removal, and concentration of samples, they are employed, yes.

One technique, dry ice slurries, is used to keep temperatures low during the process. Safety hazards, however, can arise if not handled correctly, hmmm.

A director at BMS, safety concerns recently noted. Potential risks of exploding condensers, we understand. When water builds up in the cold finger and is mistaken for acetone or not emptied, rapid expansion of the slurry can lead to shattered condensers, and physical injury to the scientists, posing a significant risk, hmmm.

Not adequately addressed, exploding condensers are, particularly in university labs. Injuries, they can cause, ranging from minor cuts to serious lacerations requiring medical attention. A report by the CDC revealed 2578 lab-associated injuries involving rotary evaporators from 2001 to 2018, with 20% resulting from shattered glassware. The second most common equipment involved in lab-associated injuries, they were, after pipettes.

Cuts, punctures, and abrasions, the most common type of injuries associated with rotary evaporators were, with the hand being the most frequently affected body part. Equipment damage and downtime, they can also lead to, negatively impacting productivity and research progress, and causing delays.

To mitigate these risks, proper training and education are crucial for scientists who use rotary evaporators. Educating lab personnel on the correct use of dry ice/acetone slurries, monitoring for water build-up in the cold finger, and appropriate disposal of the mixture after use is essential. The use of protective gear such as gloves and eye protection should be mandatory to minimize the risk of physical injury.

Expanding on the negative impact of damaged or broken equipment due to exploding condensers, essential it is to highlight the financial cost that can be incurred. An expensive affair, replacing a damaged or broken condenser can be, and in many cases, no spares readily available in the lab there may be. Result in a significant delay in replacing the broken part, this can, productivity and research progress negatively impacting. Even if the replacement part is ordered immediately, several days or weeks to arrive it may take, a major setback for ongoing experiments, this can be.

Lab guidelines and procedures should be established, to ensure that all laboratory personnel are aware of the risks associated with dry ice/acetone slurries, and necessary precautions are taken to prevent accidents and injuries. Spare parts should be readily available to facilitate the timely replacement of damaged or broken equipment, hmmm.

Don’t Worry About the Dry Ice Supply Chain Going Dry

Don’t worry about the dry ice supply chain going dry – with Ecodyst

If you’ve been keeping up with logistics news, you might have heard of the dry ice supply chain,  and how it’s taken a significant hit during the COVID-19 pandemic: with vaccines requiring temperatures as low as -70°C during transport and storage, the demand for a constant supply of dry ice really put a strain on its supply chain. On top of that, the drop in oil prices didn’t help either: Oil refinery plants produce a lot of CO2, which is then used in the production of dry ice. When oil prices dropped, production went down, and in tandem with it, dry ice production. 

Dry ice is also used in food processing facilities, which includes but isn’t limited to wineries, meat processing facilities, and bakeries. It helps maintain critical temperatures which reduces spoilage during production, slows yeast growth which also delays fermentation, and inhibits the growth of different bacteria. However, the rapid and reproducible freezing of small samples isn’t the only use of dry ice: if you’re operating a rotary evaporator in your lab, you need a good coolant for your solvent to vaporize properly inside of the rotary evaporator. With the dry ice supply chain going dry, this might be an issue. 


No dry ice and no coolants to replace with the Ecochyll X1 and Hydrogen

Traditionally, recirculating chillers have been the go-to for most labs dealing with dry ice shortages. However, chillers come with a prominent set of draw backs. First of all, they take almost forever to get cold (anywhere between 30 minutes to an hour), their cooling power decreases rapidly at lower temperatures, so achieving certain temperatures requires extremely powerful chillers with a substantial price tag, and they’re quite heavy and bulky. And they need a significant amount of coolant liquid, which is rarely water due to its relatively high freezing temperature (that and the risk of the inside of the chiller freezing up). 

The Ecochyll X1 and the Hydrogen by Ecodyst both bypass all these drawbacks.  

“Since we switched to the EcoChyll X1, we can now avoid the use of dry ice for evaporating compounds. Sometimes there is no more dry ice in the building, and so that accelerates our research quite a bit. We don’t have to wait for dry ice to arrive, we can just keep working.” -Vincent Lindsay, Assistant Professor at NCSU

Here’s a bit more info on the Ecochyll X1 and the HYDROGEN

Ecochyll X1 Hydrogen
Tankless Cooling System Shortens run times
Cools to -10°C in 1 min and -40°C in 5 min Cools to -10°C in 1 min and -40°C in 5 min
Footprint under 1 ft2 0.1 m2 Reduces electricity consumption by 50%
No dry ice, no coolants to replace Smaller footprint than a rotovap and chiller
Virtually no maintenance  Eliminates the need for all coolants and dry ice

The Importance of Proper Vacuum for Rotary Evaporation

Using a vacuum source with your rotary evaporator comes with a significant set of advantages, like making your processes safer, more efficient, cleaner, and overall, easier. In this blog post, we’re going through all the reasons why owning a rotary evaporator is typically paired with using a vacuum source (either built-in or a vacuum pump).

Depending on the rotary evaporator you’re using, you might already have a built-in vacuum controller and you’ll only need to add a vacuum pump. However, if this isn’t the case, you’ll need to invest in both a pump and a manual (or digital) controller. Controllers don’t come cheap, but there are a few ways to decrease your cost (That we’ll discuss in a future blog post – stay tuned!).  

Controllable vacuum sources allow you to adjust the pressure with surgical precision, providing you with the desired evaporation rate. An increase in evaporation rate can therefore be achieved without having to upscale your bath’s temperature, which will allow you to achieve evaporation rates previously unattainable using a bath alone. Using a vacuum source also leads to improved solvent-product separation thanks to the controlled and even evaporation rate. It also decreases the risk of bumping (the formation of bubbles due to hasty boiling of samples; This can lead to your sample splashing out of the flask.). 

In regard to safety, using a vacuum source mitigates many risks. The decrease in boiling point of certain temperature-sensitive compounds reduces the odds of them reacting in your mixture. By reducing the pressure inside of the flask, and in tandem with it, the boiling point of your solvents, you can remove high boiling solvents in a quicker (we’re talking a few minutes, or even seconds) and safer manner. Inherently, you can work at lower bath temperatures, and use water instead of oil in heating baths. This is a safer option since using oil can leave behind residues in your evaporation flask which constitutes a fire hazard in the presence of flammable gas vapors. 

To sum it up, vacuum makes your processes safer, cheaper, and even easier (specially in cleaning – ever tried cleaning up oil off of your machine?).  

Setting the Right Rotational Speed for your Rotary Evaporator

When operating a rotary evaporator in your lab, you want to make sure that you’re being as efficient as possible. One of the main factors to be considered is the rotational speed of your rotary evaporator, and while it might seem like maxing it out is your best option, it might not always be the case. You wouldn’t want things to spin out of control now, would you? Some of the factors that you need to keep in mind when operating your rotary evaporator at its upper rotational speed is mechanical damage to your equipment caused by high speeds, and the decrease in evaporation rates beyond said speeds. And while certain studies postulate that the optimal speed lies somewhere between 250 to 280 rpm, it isn’t truly a definite rule of thumb. In this post, we’ll discuss the factors you need to take into consideration when setting the rotational speed of your rotary evaporator to make the best out of your processes. 


High Speeds and Potential Equipment Failure

High speeds are synonymous with an increased risk of equipment damage, mainly in two forms:

  • Vibratory forces which increase the wear and tear of the evaporator
  • Mechanical problems with the evaporator

Studies have shown that there is a linear relationship between mechanical failure and higher rotational speeds. Another thing worth noting is the increase in spillage risk due to the higher turbulence in water baths when operating at higher speeds. 


High Speeds and Evaporation

The rotation of the flask in a rotary evaporator leads to an increase in the surface area of the liquid inside of the flask, which increases the evaporation rate. The rotation also leads to an increase in the agitation of the liquid in the water bath. This improves the heat transfer to the flask, and the solvent. Both of the aforementioned factors depend on the rotation of the flask. Intuitively, one would think that an increase in the rpm of the evaporator would result in quicker evaporation, but this applies only to a certain degree. A study by Buchi showed that at rates above 400 rpm, the rate of evaporation started decreasing. The sharp increase in centrifugal forces eventually leads to the particles inside of the flask pressing up against the walls, decreasing the turbulence and eventually the evaporation rate. 

Simply put, you want to maximize the turbulence to achieve the highest evaporation rate. This will require you to factor in the flask size, the fill level (make sure to minimize the risk of both foaming and bumping to avoid contaminating your sample), the solvent, and sample consistency. 

One last thing you want to avoid  is any liquid sealing off your vapor tube. This could lead to the formation of a bubble that pushes the liquid up the vapor tube, contaminating the collection flask almost instantaneously. 


Optimal Rotation Speed

While 250 to 280 rpm works best for most rotary evaporators, some of them operate better at other speeds. This is particularly true when considering different sizes of rotary evaporators; a larger rotovap will almost always have a lower ideal speed (and lower maximum speed) than a smaller rotary evaporator of the same brand. Similarly, flask size will play a role in the ideal rotation speed as well, with smaller flasks meriting a higher rotation speed. The takeaway: read your user manual, and find the sweet-spot between speed and equipment wear. 

NIRvana Sciences Purchases EcoChyll X1 Rotovap Chiller

RESEARCH TRIANGLE PARK, NC, May 1, 2022 – NIRvana Sciences, Inc., the leading developer of synthetic bacteriochlorins and chlorins, today announced that it is purchasing an environmentally friendlier chiller for its rotovap system from Ecodyst, a local company in Apex, North Carolina.

Chris MacNevin, VP of Operations, said “We recently retrofitted one of our existing rotovaps with the Ecochyll X1 chiller unit and are very happy with its performance. A simple flip of the switch and the chiller is ready to go in minutes. It’s great to be free from the hassles of dry ice – no more constant refilling of the trap during solvent collection. So far it has worked well with all typical solvents with no noticeable solvent pass through. Convenient temperature control also allows for removal
of water without excessive frost buildup. Thanks to George and the team at Ecodyst for putting together a great product!”

About NIRvana Sciences
NIRvana Sciences is a spin-out from North Carolina State University with a mission to commercialize red and nearinfrared fluorescent dyes and associated probes and beads with narrow spectral properties for use in life science applications. In addition to support from NIH, NIRvana has also received support from angel investors in North and South Carolina, North Carolina Biotechnology Center (NCBC), NC IDEA and Blackstone Entrepreneurs Network. NIRvana facility is located at Alexandria Innovation Center in Research Triangle Park, NC USA.


Source: NIRvana Sciences

North Carolina State University Case Study

EcoChyll X1 & Hydrogen accelerating organic synthesis R&D at North Carolina State University.

NC State Case Study Brochure

The Rule of 20: setting the right temperature for your rotary evaporator

You just bought your rotary evaporator, you set it up on your benchtop after making sure to follow the manual instructions word for word. Everything’s all set and you’re ready to get some work done with your evaporator. And then it hits you: What temperature should you set your rotary evaporator to? Enter the “Rule of 20”, AKA the “20/40/60 Rule” AKA the “Delta 20 Rule”. 


The Theoretical How

In a nutshell, the Rule of 20 states that the temperature of your coolant should be at least 20 lower than the vapor’s temperature, and that your bath’s temperature should be 20 higher than the vapor temperature or boiling point your are trying to reach. Let’s say that the boiling temperature of your substance is 30. You’ll need a coolant temperature of 10 and a bath temperature of 50 to be operating under optimal conditions. 


The Why

By following the Rule of 20, you’re trying to find the perfect balance between energy usage and process efficiency: Higher bath temperatures merged with lower coolant temperatures increase the distillation’s efficiency. But there’s a catch: the higher the temperature of your bath and the lower your coolant temperature, the more energy you end up spending. This means that at a certain point, investing more energy into your process won’t be impactful on the overall efficiency of the process anymore. 

The Rule of 20 bypasses this issue by ensuring an efficient distillation. 

You should keep in mind that in certain scenarios, like working with heat-sensitive compounds, you might be forced to keep your bath’s temperature at levels lower than the one advise by the Rule of 20.


The Practical How

Now that you’re all set, it’s time to evaporate some solvents! In certain scenarios, and with a bit of luck, you might be able to apply the 20/40/60 rule literally: Simply set your bath temperature to 60, your coolant to 20, and your vapor temperature to 40 using your vacuum controller. By applying vacuum and reducing the boiling point, you can use the same temperature settings for most common solvents. We thought we’d save you some time: you can find the vacuum pressures of some common solvents below. 

Solvent Boiling Point (°C) Solvent
Acetic Acid 118.0 Ethyl Acetate
Acetic Acid Anhydride 139.0 Ethyl Ether
Acetone 56.3 Ethylene Dichloride
Acetonitrile 81.6 Ethylene Glycol
Benzene 80.1 Heptane
iso-Butanol 107.7 n-Hexane
n-Butanol 117.7 Hydrochloric Acid
tert-Butanol 82.5 Methanol
Carbon Tetrachloride 76.5 Methylene Chloride
Chlorobenzene 131.7 MTBE
Chloroform 61.2 Pentane
Cyclohexane 80.7 Petroleum Ether
Cyclopentane 49.3 iso-Propanol
Dichloromethane 39.8 n-Propanol
Diethyl Ether 34.6 Pyridine
Dimethyl Acetamide 166.1 Tetrahydrofuran
Dimethyl Formamide 153.0 Toluene
Dimethyl Sulfoxide 189.0 Trifluoroacetic Acid
Dioxane 101.0 Water
Ethanol 78.3 Xylene

While the rule of 20 is a good rule of thumb for most evaporative procedures, there is one aspect where it doesn’t hurt to overshoot: cooling. There is no downside to having the coolant even colder than 20 below the vapor temperature, and in fact it can help improve evaporation rates to do so. This increases solvent recovery, making your process as efficient as possible.  This is where chillers come in, but there’s a trick: chillers lose cooling power as they operate at colder temperatures due to less efficient heat transfer. Enter EcoChyll: by pumping refrigerant directly through the condenser coils from the compressor, the EcoChyll gets colder much faster, and can maintain very low temperatures better than what would be considered a suitably sized chiller hooked up to a rotary evaporator.