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Product Focus: Microwave Digesters

When preparing a sample for analysis that requires high temperature and pressure in an acidic environment, a scientist selects microwave digestion for the process. This attracts scientists from an extraordinarily large range.

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Consider Your Chemistry for Today and Tomorrow for Higher Savings

 “Microwave digestion uses are extremely broad,” says David Gunn, applications manager at Milestone (Shelton, CT). “It includes processes in the food industry, pharmaceuticals, precious metals, mining—just about anything where you analyze trace metals.”

Furthermore, microwave digestion impacts not only what you want to do but also how you want to do it. Bob Lockerman, analytical product manager at CEM Corporation (Matthews, NC), explains, “Microwave digestion is typically used for throughput, when people want to speed up sample preparation.”

Stay out of the hood

To keep a microwave digester working properly as long as possible, users should follow a few guidelines. “Keep these systems out of the fume hood and away from corrosives,” says Lockerman. “Don’t sit it near a bottle of acid.” He adds that all manufacturers build these devices so that the air inside the vessel does not get to the electronics, but he adds, “The electronics have to breathe, and they collect air from outside the cavity. If you put the digester in a heavy acid environment, that will affect the electronics.”

Maintenance of a microwave digester also includes another step. “Inspect the vessel,” Lockerman says. “Look for wear and tear.” He mentions that most manufacturers provide specific guidelines for inspecting the vessel. Gunn adds, “Make sure that your chemistry matches up to the specifications of the vessel.”

Like any technology, a microwave digester does the job right only when it’s used properly. When asked about the most common mistakes in using this device, Lockerman says, “It’s putting the vessel together incorrectly.” He adds, “The vessel should be simple to put together, so there’s less chance to make a mistake.”

Another common mistake, says Lockerman, happens when users put in too much sample.

Buying tips

At Exova (Santa Fe Springs, CA), Peter Espinoza, sample prep coordinator for the inorganics group, says, “We analyze every element on the periodic table.” Depending on the process, he needs different temperatures. “For really difficult samples, like plastics and polymers,” he says, “we use up to 250 degrees and 40 bars of pressure.” To keep his systems running properly, he says, “We try to follow the recommendations from the manufacturers, and we have a service plan, so they come out once a year.”

Espinoza’s comments make a perfect introduction to Gunn’s key buying tip: “When shopping for a new microwave digester, make sure that it has the ability to do all of your samples.” He adds, “It must cover all of your samples and provide the throughput that you need.”

The samples that Gunn describes should be for today and the near future. “Think down the road,” he says. “What will I need in the next ten years?” Although that can be difficult to predict, it’s worth a try. “If you suddenly go to something more difficult,” Gunn says, “you might need a new device.”

So when buying a microwave digester today, it helps to think about the chemistries that you might run tomorrow. Considering tomorrow’s necessary temperatures and pressures could save you money now and in the future.

For additional resources on Microwave Digesters, including useful articles and a list of manufacturers, visit