In 1950, the late biochemist Lyman C. Craig of The Rockefeller University developed a simple rotary evaporator. The first commercial version came from Walter Buchi in 1957. A rotary evaporator is a lab instrument that allows people to do chemical separation or purification by using heat and agitation—or stirring—under vacuum. “You’ll find one in any chemistry lab,” says Jim Dawson, president of Heidolph North America (Elk Grove Village, IL).
As Jeff Reid, product specialist at BUCHI Labortechnik AG (Flawil, Switzerland), points out, “You can use a rotary evaporator to separate a solvent from a compound of interest.” He adds, “Solvent recycling is big as well.” This technology can also be used in other applications, such as crystallizing samples.
“There used to be just a few configurations of rotary evaporators,” says Dawson, “but now there are more options—different configurations to choose from and more manufacturers.”
Enhancing safety is a key trend in this technology. “Many researchers want the ability to safely control a rotary evaporator outside the fume hood or away from the chemistry,” Dawson says. “This doesn’t mean a remote such as a TV remote, but a small wired operating panel that allows the chemist to control the process going on inside the hood at a safe distance.” He adds, “It basically helps to protect the scientist from the chemistry.” Still, chemists often want to watch the process. “Chemists still do lots with their eyes, like visualizing [whether] something is changing,” Dawson explains.
Beyond safety, users want very low maintenance. “All researchers now have to run at higher levels of productivity, and downtime has to be minimized,” Dawson says. “So price isn’t always the game.” He adds, “The keys are the total cost of lifetime ownership and productivity.”
Beyond controlling a rotary evaporator from outside a hood, some users want additional control with the technology itself. When asked about recent trends, Reid says, “Researchers want a system where you can control all of the components—the chiller, the vacuum pump, and the rotary evaporator itself—together.” He adds, “An all-in-one system can save 75 percent in energy. In such a system, for example, the vacuum pump produces the needed level of vacuum and then holds it, instead of running continuously.”
Users can also build a system from various vendors and run them all from one controller. John Pollard, vice president of sales at BUCHI, says, “Our controller and some of our competitors’ controllers can control other brands, but you lose the green functionality.” When building a system from various components, for instance, the controller might display the vacuum but not turn off the pump when it reaches the desired level. “It’s more automated when it all comes from a single manufacturer,” Pollard says.
An all-in-one system also enhances the simplicity of using a rotary evaporator, which Pollard says is near the top of the list among customer desires. “In an academic market, you could have 100 users of one rotary evaporator.” So that machine needs to be easy to use.
In some cases, the use is easy enough but, as Reid says, “The trick is to find the right parameters.” He adds, “So we provide those for the most common solvents.”
From the field
For a rotary-evaporator customer, two questions should be considered. First, will the rotary evaporator work as the manufacturer says it will? Second, if something goes wrong, will the customer have support to get it running again? “Chemists know things will go wrong,” Dawson says, “because they are using volatile chemicals and acids.”
Alfred Bacher, Ph.D., of the department of biochemistry at the University of California, Los Angeles, teaches lower-division organic laboratory courses and the upper-division inorganic/organometallic laboratory course. He says, “In all of these courses, we use
rotary evaporators very heavily, particularly in the lower-division courses, because the solvents being used are flammable.” Based on working largely with undergraduate students, Bacher would like a range of improvements in rotary evaporators. For one thing, he’d like lower-cost versions because, he says, “The cost of the rotary evaporators is too high to be used in larger numbers in undergraduate laboratory courses.”
In addition, Bacher desires some design improvements. “Overall, the design seems to be very intimidating to many of my undergraduates,” he says. He’d also like the design to “allow for an easier disassembly of the setup for maintenance.” In fact, he’d like less maintenance overall. For example, he says the seals that connect the condenser unit with the motor are “not as robust” as they could be. Maybe, Bacher suggests, a rotary evaporator could include fewer joints in general to reduce the sources of leaks. For example, he says, “While I do understand why the receiving flask is attached with a ball joint, I feel it generates a significant problem as well because most round-bottom flasks used in the lab have normal ground glass joints.” Even adding a simple pressure gauge would be nice, Bacher notes.
Some problems can even be costly. As Bacher says, “The speed of lowering the assembly is too high in some models or a low point cannot be set to avoid the destruction of the vapor duct, which happens frequently in undergraduate laboratories.”
Nonetheless, Bacher realizes that many factors come into play in device design. So he describes his suggestions as “some of them being realistic, others probably not so much.”
Beyond the lab, rotary evaporators also appear in new markets. For example, some chefs use a rotary evaporator to distill liquids that they use over foods, like pouring on a high-tech reduction. The increasing simplicity of using this technology, such as the availability of all-in-one systems, should lead to even wider circles of use.
For additional resources on Rotary Evaporators , including useful articles and a list of manufacturers, visit www.labmanager.com/evaporators