Sample integrity versus storage temperature. What can we learn from penguins?


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A new report from the National Academies of Sciences, Engineering and Medicine addresses concerns about reproducibility and replicability in scientific research. Sitting near the top of the “food chain”, it is imperative that sample management provides high quality samples to researchers from the outset to “do it’s bit”.

Whether you store small molecules or biological samples the most important factor here is to protect the sample’s integrity as best you can. Reduced sample integrity can potentially result in the loss of precious data points, or unreliable data from which decisions are made.

Within the area sample management, applying some rigor to the process by which samples are processed, preserved and stored is key. Observing the correct conditions and temperature for the sample type and maintaining this for the lifetime of the sample might sound like common sense but there could be a couple of weak points in your workflow you haven’t thought of?

1)      Racked, versus rack-less storage solutions

Let’s talk about use of racks for instance. Storing tubes without racks in manual freezers is not practical and for some automated storage solutions is just not possible I hear you say! This is true to a point but there are alternative options and for very good reason.

This is where the Penguins come in! For consistency, sample storage conditions should be uniform with each sample experiencing the same freeze profiles.


We investigated the sample freezing and sample picking profiles of racked 1.4 mL vials each containing 0.97 mL volume in manual -80°C freezers. Very different freezing profiles were observed depending on vial location in the racks and rack location in the freezer. Essentially, a ‘penguin effect’ was described where outer samples froze within five to twenty minutes while inner samples took over one hour. Our test revealed a seventy-minute difference between outer and inner samples reaching -40°C, highlighting a significant insulation effect for inner vials that

2)      Don’t keep opening the door!

For the bakers amongst you, you will know that opening the oven door can be quite detrimental to the rise of a cake. 

Similarly, we discovered the repeated opening and closing of the freezer door during sample picking can do more harm than you might expect to the innocent samples that remain in the freezer. 

Our tests demonstrated that the monitored temperature of samples in a freezer during one hour of picking were warmer than -70°C, with samples nearest to the door reaching -55°C. Don’t think that because you have an automated solution you are entirely protected from repeat freeze/thaw effects! Make sure you ascertain the environmental temperature used for cherry-picking samples from racks for delivery as these can often be much higher than the main store. Why is this important? For biological samples freeze/thaw can lead to sample degradation, whilst compounds can suffer from precipitation issues.

3)      Protect innocent samples

So, by way of wrap up, what value do you put on quality assurance? Is the protection of innocent samples as high on your agenda as it is ours?

If so, make sure you choose automated storage systems that demonstrate great care and attention to sample integrity. Eliminate the “penguin effect” with rack-less automated storage solutions that ensure all tubes experience the same freezing profile. Protect innocent samples when cherry picking by maintaining a closed air exchange to minimize temperature fluctuations. By doing so, you’ve played your part in ensuring reproducibility and replicability in science.

Considering automation for biostorage? Download our new white paper: Garbage in garbage out! Are your samples fit for purpose?