The process of freeze drying, also known as lyophilization, removes water from a sample. This may be required for certain analyses, or to safely store samples. Although freeze drying is a well-known technique, it still comes with some hurdles.
“Challenges with freeze drying include reaching a low enough temperature for the sample’s eutectic point, meltback when the sample is drying, knowing when the sample is dry, maintaining a deep enough vacuum and vacuum-pump maintenance,” says Allison Schach, dealer marketing manager at Labconco.
To overcome these issues, Schach offers several suggestions. “Before selecting a freeze dryer, know the eutectic point of the samples you’ll be working with,” she says. “Then, choose a freeze dryer that reaches a lower temperature.”
In buying new equipment, some scientists like the idea of saving bench space. Knowing that, Schach says, “It may seem attractive to select a smaller, home-use freeze dryer for light use, but these units rarely meet the temperatures needed for laboratory applications and are often constructed with lower-quality materials.” Instead, look for a real lab device, something made from materials like stainless or steel polytetrafluoroethylene for corrosion resistance.
Once water is removed from a sample, it is important to prevent its return, referred to as meltback. “Meltback can damage a sample, so you want to be sure your freeze dryer maintains low enough temperature and deep enough vacuum that moisture doesn’t get back into the sample after it starts drying,” Schach explains.
How can you tell when the freeze-drying process is complete? That turns out to be more complicated than expected. “Knowing when the sample is dry can be hard to determine and often involves visual inspection and guesswork,” Schach notes. “Using an end point determination system can trigger an alert for the user when total dryness has been reached.” That’s a feature that could save time and samples.
Another feature to consider before making a purchase is the vacuum potential. “Maintaining a deep vacuum is important for successful lyophilization,” says Schach. “It’s important to select one with a high enough displacement capacity for your freeze dryer.” The manufacturer can confirm the vacuum performance for a specific model, size, and required freezing temperature. “Maintaining your vacuum pump is just as important as selecting the right one,” Schach explains. “If you have an oil pump, such as a rotary-vane vacuum pump, it’s important to keep it clean and change the oil regularly.”
Some customization also turns a freeze dryer into the right fit for specific applications. “Accessories can help you overcome challenges,” says Schach. “Having the right accessory for your sample type and size can help ensure the best results.”
Like many other devices in a lab, several features and capabilities should be kept in mind when shopping for a freeze dryer. Then, an add-on or two can fine-tune the performance for specific samples. Throw in some regular maintenance, and a scientist should be able to perform freeze drying as needed.