energy just as well,” says Chris Wilkes, product director for Thermo Fisher Scientific’s (
www.thermoscientific.com) cold storage business.
Similarly because Stirling Ultracold’s cooling system is much more com- pact, “for a given height, we use less of that height for the cooling system, so our storage capacity per square foot of floor space is substantially higher,” notes Lane.
A variety of racking and shelving solutions are available for efficient storage of tubes, vials and microplates, for example, to fit almost any freezer. “There are only a few different types of configurations of racks for uprights—usually they’re four or five boxes deep,” says Wilkes.
Most upright ULT freezers feature a single outer door and several inner doors—which may or may not be insulated—to help keep air from fall- ing out of one level of the cabinet when the outer doors are opened to access another level. Thermo Fisher Scientific offers an optional double outer door version of the Forma line: “the bottom is used more like a chest freezer—archival samples are stored in the bottom, and then working samples are stored on the top,” explains Wilkes.
Making sure that the temperature stays within range is important for maintaining the integrity of the stored samples in the event of a power outage or other failure. “Alarm systems are absolutely standard, and a backup battery to control alarm systems and control set[point] is also standard,” Wilkes points out, urging users to make sure the alarm is
properly connected to a building management or other monitoring sys- tem in order for it to do its job. Many ULT freezers can also be equipped with an optional CO2
or liquid nitrogen backup, allowing cold gas to be injected directly into the cabinet if the temperature gets too high.
Choosing a ULT freezer When the Biospecimen and Processing Core Laboratory at Mayo Clinic
(
www.mayoclinic.org) moved and expanded last year, they took the op- portunity to evaluate several different freezer solutions in terms of such metrics as capacity, temperature profile under light-to-moderate and moderate-to-heavy usage, temperature stability both with and without power, initial cost and lifetime cost and ease of use. Director Mine Cicek explains that for her biobank maintaining sample integrity ultimately trumps all else: “If I have an upright freezer that I use daily for putting samples in and pulling samples out, then I want an upright freezer that can cool back down quickly when I close the door.” After that comes cost and ease of use.
Most purchasers don’t have the luxury of simultaneously putting multiple ULT freezers to the test under controlled conditions over an extended period, and there is no industry standard as to how vendors should do so, Wilkes explains. In addition, “you can’t just look at the display and deter- mine what’s going on because temperatures displayed on the front of the freezer are kind of a rolling average, or controlled by some other algorithm.
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AMERICAN LABORATORY • 39 • MARCH 2015
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