Rotovaps: Are Rotary Evaporators Outdated in Solvent Recovery?

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A rotary evaporator is a vacuum-like device that effectively recovers solvent from a sample using evaporation. With the help of a pressure control monitor (PCM), rotovaps can precisely regulate pressure within a system to increase evaporation efficiency. 

How a rotovap works is by mechanically rotating a flask containing the compound in solution in a heated water bath. The rotovap is connected to a vacuum pump that then reduces the pressure above the bulk solvent and facilitates the recovery of the solvent away from the sample.  

The solvent evaporates while the compound remains, thus removing the solvent from the sample. 

The different boiling points in a vacuum between the solvent and the compound mixed in the solution are the key factors that allow the rotovap to work effectively. If the solvent and the other compounds have similar boiling points, it is difficult to effectively remove the solvent from the solution via a rotovap.

What are the challenges associated with rotovaps?

Rotovaps have been around since the 1950’s and have been constantly upgraded throughout the years. Since the fifties our glass integrity has increased, our technology has been upgraded with the introduction of a PCM, and the ability to cook solvent at a higher temperature has increased.

Yet, despite this, no amount of upgrading, researching, or redesigning has seemed to solve the underlying issues of the rotovap.

Issues include slow evaporation time, lack of efficiency when dealing with small samples, and bumping during evaporation. Let’s take a look at these in more detail:

  1. Bumping is a common problem while using rotary evaporators. Samples being heated under vacuum in closed conditions causes the solvent to suddenly boil and “bump,” in other words erupt, usually quickly without warning. As the rotovap evaporates the solvent under vacuum, the solvent can be sucked up in its entirety, leading to the loss of the sample - not to mention the loss of time and money for the company. 

  2. Due to their inherent technological limitations, evaporating solvents with rotary evaporators can be painfully slow, especially for high boiling point solvents, such as DMF (Dimethylformamide) and DMSO (Dimethyl Sulfoxide). Researchers know that this orthodox evaporation method using a rotovap can take a very long time and is a large bottleneck in the overall synthesis and recovery process.  

  3. Working with rotary evaporators can be difficult, especially with small samples. Transferring the solvent to the rotovap, followed by painstakingly scraping the sample from the round-bottom flask, not only leads to wasted effort, lost time and loss of sample, but also presents risk of cross-contamination.

When dealing with heat, chemical compounds and solutions, and transitioning matter from liquid to gas, then there is for certain pressure changes within the rotovap. 

With a smaller sized rotovaps, the chamber is made of glass. This glass normally has a pressure range and heat range that it can withstand during the process. If during the process, the integrity of the glass fails, rotovaps have been known to explode during operation. 

On an industrial scale, manufacturing companies have come up with ways to transform the rotovap into an explosion proof, distillation equipment that effectively doesn’t break easily, and is more effective with the overall heat transfer than the original glass designs. 

How are rotovaps used in the cannabis and hemp extraction industry? 

Producing mass amounts of distillation and evaporation at once, rotovaps have turned into these large-scale stainless-steel containers that distill mass amounts of solvent at once. This has led to the rotovap playing a key role in cannabis and hemp extraction and production.

Extraction technology has evolved and changed the way we consume cannabis and hemp.  The rotovap plays an integral role in the extraction process because it efficiently removes extraction solvents by evaporation, without harming the product. 

Typically, the rotovap is used in post-extraction processes like refinement or recovery after ethanol extraction. Some of the purest concentrates are created with extraction methods that utilize solvents like butane, propane, or ethanol to extract cannabinoids and terpenes from trichomes. 

These methods include a purging process that removes solvents from concentrates. Traditional evaporators have a vacuum pump and offer a water chiller as an optional component.  

Interested in learning more? Get in touch with Maratek today. We’ve created innovative cannabis and hemp extraction equipment that help your business create a pure, high-quality product.

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