This technology dries glassware, controls crucial experiments and more

Lab ovens appear in many settings, from basic research to industrial work. Moreover, scientists can choose from a wide range of options.

“In the scientific world,” says Uwe Ross, president at BINDER (Bohemia, NY), “60 percent of the ovens are used for simple drying, and most of the drying is glassware and sometimes plastic.” Furthermore, some scientists like lab ovens just they way they are. For instance, Ioana Pavel Sizemore, Ph.D., assistant professor of physical chemistry at Wright State University (Dayton, OH), does not see anything in particular that she would change about lab ovens. Nonetheless, she did make a comment about using them: “I would recommend that students be careful about what kind of labels they use for beakers, to avoid fire.”

Still, the past couple of decades have brought big changes in lab ovens. Not all that long ago, some lab ovens required a user to put a thermometer inside and adjust the dial until the oven reached the desired temperature. “Today’s state-of-the-art oven is digitally controlled,” says Ross. “We’ve come a long way, and people now just think of this as, ‘I need some heat and the rest is irrelevant.’” That type of thinking, Ross adds, means “lots of people don’t know how to select the right product from the many lab ovens available.”

Accuracy all over

Part of the choice of a lab oven depends how much accuracy a user needs and whether that accuracy needs to exist throughout the oven. This is called “spatial temperature accuracy,” which Ross describes as “meaning that the temperature is really what the indicator displays, and not just in one spot.” Providing such spatial accuracy depends on a combination of insulation and the approach to heating. “The way you heat is the root cause for introducing the same temperature across the entire oven,” Ross explains. “Plus, the controller algorithms need to react quickly to changes to keep the same temperature.”

Even the door on an oven greatly affects spatial temperature accuracy. “The door makes all the difference in the world,” says Ross. He mentions that the doors on many lab ovens are so poorly adjusted that a piece of paper can be slipped through at the edge. That problem leads Ross to say, “People think of a lab oven as a commodity that they can use for a dozen years without any maintenance, and that’s just not the case.”

Ross and his colleagues recommend oven maintenance at least every two years. “You start seeing door seals go or the door needs adjustment,” he says. “Things need calibration because they’ve been mistreated, like something banged against the sensor.”

Heating up chromatography

Beyond drying glassware, lab ovens play important roles in analytical processes, such as high-performance liquid chromatography (HPLC). “There are two categories of HPLC ovens,” says Bert Ooms, principal scientist at Spark Holland (Emmen, The Netherlands). “One is block heaters, where you clamp the column between pieces of metal.” In essence, such heaters protect the column from temperature variations. As for the second type, Ooms says, “We sell forced-air ovens, which include a chamber in which air circulates at high velocity, and this has much better heat transmission between the air and the column.” He adds that the second category of HPLC ovens provides better temperature control.

In many modern HPLC applications, researchers want to replace largely organic solvents Lab Ovens This technology dries glassware, controls crucial experiments and more “Lots of people don’t know how to select the right product from the many lab ovens available.” September 2012 Lab Manager 65 with water that includes some organic modifiers. “This is called ‘green chromatography,’ and it requires ovens that go higher than 150 degrees Celsius,” Ooms says. “Today, there are more columns that can withstand those high temperatures.” As an example, he mentions carbon columns from Thermo Fisher Scientific (Waltham, MA).

Ooms also points out that many researchers now use ultraHPLC (uHPLC), which uses even smaller particles in the separation column. “If you want to use standard equipment for high resolution,” Ooms says, “you can use core-shell particles, which are only superficially porous and higher temperatures from the oven.” He adds, “The grouping of a higher temperature for separation and core-shell particles is a nice combination for high-resolution chromatography with a traditional HPLC system.”

If an HPLC comes with a block heater, a forced-air version can be added. “It’s easy to add,” Ooms says. “It just goes between the automated sampler and the detector.”

Evolving options

In 1978, Engineered Product Sales (Orange, CA) started selling ovens for pharmaceutical and industrial applications. Over the past few decades, company president Ken Klein watched the industry develop. “Some years ago,” he says, “the builders seemed to stay with cheaper materials for the interiors, like aluminized steel, but they started switching to stainless.”

Beyond an evolving manufacturing industry, Klein sees changes in the customers. “Most of the people who buy lab ovens tend to go for the programming controls where they can ramp up and hold or ramp up and down,” Klein says. “Controls are cheaper these days, and it’s a very minor upgrade to go from a single set point unit.” He adds that the simplest units still have a thermometer sticking out of the top to show the internal temperature. If someone buys one of those, though, “more often than not they come back and wish they’d purchased something else,” Klein says.

Users can also choose between gravity and forced convection. In the former type, hot air moves naturally from heating sources. With the latter, blown heat flows from many locations and across all of the shelves. “Forced convection is not that much more expensive, and it seems to be winning out,” says Klein.

The increasing number of options gives scientists and engineers more ways to use lab ovens. In essence, anybody who manufacturers something or runs research probably uses a lab oven. Plus, the results turn out more accurate than ever.