Maintaining sample integrity is essential for the accuracy of your medical research projects. In terms of sample management, it is of vital importance that your samples are kept at a constant freezer temperature. Even a short exposure to warmer temperatures can degrade the quality of your samples and unfortunately with older style manual freezers, it is sometimes hard to avoid.
Herein, we will discuss some instances where sample degradation can potentially take place.
There are often processes that take place at the sample collection stage that can inadvertently lead to sample degradation. For instance, technicians often work in a batch fashion filling a rack with samples before transporting them to the storage facility. Thus, the first of these samples collected may be exposed to ambient conditions for longer periods leading to preferential degradation.
Solution – Use of a pneumatic sample transport system that deals with individual samples as soon as they are ready can overcome this issue.
Dry Ice Transportation
Sample racks are typically transported to storage facilities using dry ice as a refrigerant. While dry ice may exist at ~-80°C, the temperature in the transport container may be as of the order of -50°C due to the fact the heat is introduced by the sample trays. This has resulted in many a researcher being lulled into a false sense of security by using dry ice.
Solution – Using the pneumatic sample transport system described above can also help alleviate this issue.
Improper organisation of samples within a freezer can impede air circulation in the freezer potentially resulting in hot and cold spots within your freezer.
Solution – Pay attention to air circulation paths and organize your samples accordingly.
Opening the Door
Using traditional style manual freezers, this problem is unavoidable as you will always need to open the door to access your samples. The simple act of opening and closing the door exposes samples to warmer air. In a study that monitored sample temperatures of samples following opening the door, all samples, regardless of location reached temperatures warmer than -70°C. Not surprisingly samples at the front were worst affected. Now imagine if a freezer houses popular samples requiring repeated opening and closing. This could lead to seriously compromised samples.
Solution – The only solution here is to go to an automated sample storage system.
The Picking Process
Manual freezers typically use racks. This means that, to retrieve a single sample, you normally need to remove an entire plate of 500 to 1000 tubes from the storage conditions. This means that all the other samples are being subjected to repeated freeze/thaw cycles or thermal shocks even though they are not being called upon. The effect can be more severe when sample racks have tubes frozen into blocks that can only be separated after a degree of thawing.
This process has potentially the most severe impact on sample integrity.
Solution – Ensure the freezer atmosphere is free from moisture. Automation, with specific sample picking can also overcome this problem.
Traditional manual freezers offer a number of scenarios whereby sample integrity can be compromised. Using compromised samples can undermine the quality of your research, especially if sample integrity is not detected.
While manual freezers offer a low-cost option for sample storage, they may offer a false economy. An automated sample storage solution like the SPT Labtech arktic linked using a pneumatic sample transport system can overcome the problems with manual freezers discussed above as well as consolidating and centralizing the contents of several manual freezers and ensuring sample integrity.
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