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.

 

References:

https://brandtech.com/solventboilingpointschart/

To Fume Hood or not to Fume Hood: Should you use a Fume Hood with your Rotary Evaporator?

Rotary evaporators can be spotted in labs under fume hoods or directly on benchtops. While both options are valid, there are multiple factors that need to be taken into account when deciding whether to use a fume hood or not. This blog post puts everything on the table (or benchtop) to help you answer the age-old question: to fume hood or not to fume hood?

1-Using the Right Equipment

We know, it’s an obvious one, but if your set up is too big to fit under the fume hood, you won’t be able to use it. Your choice of hood usually boils down to the amount of space available in your lab: if your condenser is vertical, you will probably need a larger fume hood as compared to diagonal condensers that are more “space-friendly”. Both ways, safety always comes first, so we’ve compiled multiple criteria to help you make the right choice when deciding whether or not to purchase a fume hood.

2-Implosions

Implosions are most likely to occur if your glassware has cracks or fractures in it. When the glass is put under different stressors, it’s prone to break, which might lead to injury. In that case, it is advised to keep the sash closed at all times.

3-Explosions

Some applications of your rotary evaporators come with a risk of explosion; this includes but isn’t limited to the use of different chemical mixtures that carry a high risk of explosion when put under certain conditions. For instance, multiple reports have emerged recording the presence of azide with the use of halogenated solvents leading to explosions shattering the glassware of rotary evaporators.

If an explosion was to occur, bystanders would be at risk of exposure to chemical splashes and being hit by flying glass shards. Using your rotary evaporator with your fume hood’s sash always closed is one of the easiest ways to mitigate the risk of different injuries caused by an explosion.

4-High-Temperature Applications

Another reason why you might consider getting your rotary evaporator a fume hood is high temperature applications. Say you’re using an oil bath and you’re heating it to temperatures at or above 100°C to perform a high-temperature evaporation; leaving it unattended might pose a prominent safety concern. You might be wondering what the best way is to mitigate that risk, and you guessed it: fume hoods.

5-Health Risks due to Fumes

Rotary evaporators should be used in well-ventilated areas. Removing volatile solvents is not a risk-free process: sometimes volatiles escape, and if present in high concentrations, might lead to explosions, irritation, and/or different respiratory illnesses. Sometimes, proper ventilation might not be accessible in your lab. In that case, once again, fume hoods are the answer.

It’s worth mentioning that some applications of your rotary evaporator might lead to the generation of toxic fumes or vapors. In that case, no matter how well ventilated your lab is, fitting your equipment under a fume hood becomes a necessity.

Getting the Job done without a Fume Hood

For whatever reason, getting a fume hood for your lab might not be an option. However, compromising your safety isn’t. That’s why we added a couple more alternatives to using a fume hood that provide you with the protection and ventilation you need to carry on your work in your lab worry and risk free.

1-Building a Safe Environment

Building a safe environment starts with you donning the right Personal Protection Equipment (PPE) if handling hazardous materials. Having the proper measures implemented inside of your lab if operating in special environments is also worth considering. For instance, certain applications should be carried out in labs that have preexisting built-in ventilation systems, and that are fully explosion proof.

2- Using an Enclosure instead of a Fume Hood.

Enclosures can be a great alternative to using a fume hood in your lab when trying to minimize exposure to fumes and vapors. It is worth mentioning that not all enclosures provide protection against both vapors and shattered glassware/ splashes,

Conclusion

Fume hoods serve one main purpose: minimizing exposure to the different risks you might be exposed to when using your rotary evaporator, namely noxious vapor and fumes, and flying shards of glass caused by implosions and explosions. Other options to consider when fume hoods are not available are either using an enclosure, or carrying out your experiments in a pre-made special environment.

Solvent Recovery vs Distillation: Which is Best?

Solvent recovery and distillation are critical processes in a range of industries. Both processes are used to separate and purify elements meaning they are helpful means of recovering a range of chemical components. This article will detail both processes and how they measure up against one another.

What is Solvent Recovery

Solvent recovery or solvent extraction is a technique in which chemical compounds are isolated in accordance with their solubilities. Solvent recovery is employed in a range of industries from vegetable oils, perfume, food, cosmetics, pharmaceuticals, manufacturing, cannabis production and mining. Solvent recovery is important because it is used to isolate hazardous materials from sediments and sludge and separate the helpful components from the debris.

An example of this is solvent recovery in the petrochemical refining industry, where it is used to separate petrol by causing them to float to the top or sink to the bottom for easy removal.

Solvent recovery is also important in the hazardous waste industry as it decreases the levels of hazardous waste that needs to be treated. Solvent recovery does not damage the substance which is extracted, just separates the compounds. These compounds are then extracted to be used for a range of purposes according to the industry. Solvent recovery is a means of purifying elements and identify different chemical components.

Rotary evaporators use evaporation to gently and efficiently remove solvents from a range of sample types, including both organic and inorganic analytes and polymeric materials. The sample is heated whilst its boiling point is lowered by a vacuum which is formed by the rotary evaporator. This means that solvent recovery is possible at a much lower temperature.

What is Solvent Distillation?

Solvent distillation is the solvent separation involving application of heat to separate a mixture of liquid of two or more two or more substances. The solvent mixture is heated to boiling point and as a vapor its piped away to a new storage container in which is will cool and condense to an almost pure quality. This results in a distilled solvent which can be reused and wastage which can be disposed of accordingly.

Rotary evaporators are sometimes used in distillation applications as it is faster than traditional techniques as solutions are distilled under reduced pressure at a lower temperature, speeding up the process because of the larger surface area.

The Key Differences Between Solvent Recovery and Distillation

The key difference between solvent recovery and distillation is that solvent recovery purifies a substance whether it is in a solid or liquid phase whereas solvent distillation can only purify a substance in the liquid phase. This means that solvent recovery can be used for more applications and is a more cost-effective solution.

Rotary evaporators from Ecodyst can be used for both distillation and solvent recovery. If you would like to find out more about how we can help you, contact us today.

Understanding how Cold Traps are Used in Vacuum Applications

Cold traps are used to condense vapors present in vacuum applications into a solid or liquid state (excluding permanent gases). The main function of a cold trap is to ensure that there is no contamination inside vacuum applications. Whilst experiments are conducted, containers must sit airtight so no vapor can escape and no extra gas can enter the chamber and cold traps work to stop this.

How Does a Cold Trap Work?

Cold traps are usually made up of two parts, the bottom being a large, thick round tube with ground glass joints. The second is a cap that also has ground-glass connections. The length of the tube is selected so that the cap reaches about half the length.

Cold traps should be assembled so that the down tube connects to the gas source whilst the cap is connected to the vacuum source. This means that vapor phase condensate is unlikely to move up the tube.

Cold traps condense incoming vapors in the chamber to inhibit contamination. It is particularly useful for the removal of large quantities of liquid in freeze-drying.

Cold Trap Applications

Cold traps are used in applications in which the process is coming over in the form of a vapor and must be trapped. There is a range of different traps that can be tailored to the chemical composition of the process.

Some processes have gasses that travel in a vapor form and can easily be trapped once rapidly cooled. This means that the vapor condenses and the condensation can be collected in the trap.

Cold traps are often used in applications that require low-temperature conditions via evaporators such as distillation and condensation. In these applications, the cold trap contains a freezing mixture of dry ice or a coolant and acetone.

Cold Traps and Rotary Evaporators

Cold traps play a critical role in traditional rotary evaporators as it traps gas on a cooled surface in a coagulated manner. The cold trap is placed in between a vacuum vessel and a pump for trapping oil vapor or adsorbing gas. The cold trap is lined with a lead gasket and connected to the vacuum pump and suction container.

The cold trap adsorbs heat from the condenser, keeping the temperatures low, and when gas passes through the water vapor and other gases solidify on the condenser. This then increases the degree of vacuum.

Why Ecodyst’s Revolutionary Technology Replaces Cold Traps

Traditional rotovaps used cold traps that require material such as liquid nitrogen or anti-freeze to cool them. However, Ecodyst’s new revolutionary technology uses continuous cooling, eliminating the need for excess, expensive, and energy inefficient cooling technology.

Cold Trap Terpene Capture—How Does it Work?

Terpenes are aromatic compounds that are present in many plants. They are commonly associated with cannabis plants as they contain high concentrations of terpenes. Terpenes create the characteristic scent of a range of plants – making up the bulk of the fragrance.

Terpenes protect animals from grazing and infectious germs but they can also have some health benefits to humans. Terpene extraction and capture usually refer to terpene in cannabis. This article will discuss the key techniques of terpene capture.

Terpene Capture is Challenging

Extracting terpenes from organic sources can be challenging and time-consuming. That is why it is important to ensure the optimum method is selected. The methods can be generally sorted into two categories: solventless and solvent-based extracts.

What is a Cold Trap?

Cold traps are devices that condense all vapors into liquid or solid, apart from permanent gases. The main reason cold traps are used is to stop vapors produced during an experiment from going into the vacuum pump as they could condense and contaminate it.

Using a cold trap for isolating terpenes involves an oven set at a very low temperature. The oven is filled with plant material under a vacuum. Terpenes have very low vapor pressure meaning they will evaporate very quickly, vacuums help to protect the terpenes from temperature degradation, allowing the change in pressure to do the work and preserve the terpene.

How do Cold Traps for Terpene Extraction Work?

Vacuum Purging

Vacuum purging is a critical aspect of solvent extraction, producing a high-quality end-product. Some terpenes are also removed during the process due to the low vacuum pressure and heat needed to remove the residual solvents.

Without a mechanism for trapping terpenes, the terpenes will enter the vacuum pump and they will likely degrade and cause damage. Using a cold trap helps to preserve the terpene vapors as liquids before they enter the vacuum pump. These terpenes can then be consumed or reintroduced to the material post-process.

Decarboxylation

High temperatures are needed to decarboxylate and this results in large levels of terpenes being lost to the atmosphere. Cold traps help to collect these volatile organic compounds.

Solvents

Terpenes are soluble in most solvents. This means that some terpenes vaporize with the solvent whilst it’s being reclaimed from the collection vessel and returned to the solvent tank. Cold traps can separate the terpenes from the solvent vapor steam.

Terpene Capture with Ecodyst

Ecodyst manufactures revolutionary evaporators that work on the same principle as traditional cold traps. The terpenes are removed from the solution before they become damaged by heat.

Instead of the time-consuming cold traps of the past, Ecodyst uses a highly efficient condenser cooling system that offers continuous cooling and rapid condensation.

To find out more about using Ecodyst evaporators in place of traditional cold traps, get in touch with the team today.

Enhanced Sustainability at the University of Oxford with the Ecodyst Hydrogen Rotary Evaporator

Rotary evaporators are found in many chemistry laboratories across the world. They have a range of uses and applications in both research and industry. They are an essential piece of lab equipment that allows for the fast and efficient removal of solvents from samples. This article presents an investigation into the differences between the Ecodyst Hydrogen and standard rotovaps used at The University of Oxford.

Traditional Rotary Evaporators

The condenser in standard rotary evaporators has traditionally been cooled using single-pass water, dry ice, or a recirculating chiller. Using water can result in the use of up to 4.0L per minute and can lead to flooding. Recirculating chillers waste far less water, however, the condenser still needs to be cooled and dry ice is often used for this.

However, dry ice can also be expensive and unsustainable when used in the quantities required for a rotary evaporator system.

 Figure 1

 Ecodyst Patented Technology

Ecodyst has developed its own patented chiller technology that bypasses cooling systems that are less energy-efficient and sustainable. The Hydrogen uses a metal condenser coil that is coated in a chemical resistance polymer, offering many advantages over standard glass condensers. The Ecodyst Hydorgen’s chiller can reach temperatures of less than -34°C.

Figure 2

Comparisons with Existing Set-Ups

Dr. Katrherine England from the Nuffield Department of Medicine, University of Oxford compared the Ecodyst Hydrogen to the department’s existing evaporator setup. This setup consisted of a Heidolph MX07R-20-HD2E recirculating chiller filled with an ethylene glycol solution, an R-200 Buchi Rotavapor, and Buchi B-490 heating bath.

Figure 3 

The Logicall Wireless Solutions energy monitors and online platform were then employed to monitor the equipment. The vacuum controllers were used at the same set points and were not part of the energy calculations.

The two systems carried out the distillation of 100ml of cyclohexane and compared. The operations were carried out separately to compare the overall performance and running costs.

Figure 4

Results of the Comparison

When comparing the two pieces of equipment we can see that the set Ecodyst Hydrogen was ten times faster than the department’s existing rotovap setup.  All of the components were ready within seven minutes whereas the department’s original rotovap took seventy minutes to achieve the -10C set point.

The Hydrogen saved significant amounts of energy, using 49.8% less than the original instrument when carrying out the 100ml cyclohexane distillation. The chiller component used 80.8% less energy to reach this setpoint than the recirculating chiller and once it had reached this point it used 64% less energy overall.

Another benefit of the Hydrogen is that it only takes 5 minutes to reach the point of the chiller being ready. This means that it can be switched off when inactive.

Find Out More

This investigation shows that the Hydrogen rotary evaporator from Ecodyst uses far less energy than its more traditional counterparts. If you would like to learn more about how Ecodyst can help you streamline your vapor condensing practices, get in touch with the team today.

 

How to Choose the Right Cold Trap

Cold traps safeguard vacuum pumps from being contaminated by vapors being condensed in the device. They also stop oil vapors from backstreaming from the pump back to the system, making the vacuum pumps more efficient and less likely to break down.

In this article, we discuss the types of cold traps available and their benefits and applications.

What is a Cold Trap?

Cold traps are a fundamental part of solvent recovery and are used in vacuum applications where a range of vapors are present. Cold traps condense these vapors into either a solid or liquid state, stopping contamination in the vacuum pump and minimizing the maintenance needs.

Liquid Nitrogen Cold Traps

These solvent recovery systems are of the cold thimble design, meaning the surface of the device contains liquid nitrogen at -187°C. The surface is exposed to the vacuum system and condenses molecules rapidly in the vapor phase. This action leads to a trapping effect, achieving a lower base pressure and a high pumping speed.

Stainless Steel Cold Traps

Cold traps made from stainless steel are popular because stainless steel has so many beneficial attributes. It is corrosion-resistant, meaning coming into contact with vapors will not damage the material.

Stainless steel is also beneficial for cold traps due to how hygienic it is, being extremely easy to clean and sanitize.

Traditional Cold Traps 

Traditional cold traps are extremely inefficient as they need to be extremely cold. This temperature means that large amounts of nitrogen, large amounts of tap water, and anti-freeze would be employed to safeguard the temperature.

Using these materials can be extremely expensive and use excessive amounts of energy. This can increase your company’s overheads and the environmental impacts.

Revolutionary Cold Trap Alternative from Ecodyst

Ecodyst has designed and produced a revolutionary new technology that is an end to the costly and time-consuming practices associated with traditional cold traps.

Ecodyst’s system involves a high-efficiency cooling system that we have produced to offer rapid condensation, continuous cooling, and decrease evaporation time.

Want to Find Out More?

Get in touch with the team at Ecodyst to find out more about how our cold trap alternatives can help with your recovering solvent needs.