[2026 update] Storing lyophilised material long term: what governs the shelf life posts 61–90
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Following this. I have the same question and no better information than the first post.
Where I part company with post #59, and it is a narrow parting.
The confident answers on Storing lyophilised material long term and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category.
Post #63 is the version of this I will quote in future. One addition.
Adding the boring version of Storing lyophilised material long term, because the interesting version keeps getting posted and the boring one is usually right.
Check the ordinary explanations, in order, and stop when one of them accounts for what you are seeing. Most of the time the second one does.
Visible particulate is a strong signal in the other direction: it is a reason to stop and ask rather than to filter and proceed.
The short version is the first sentence; the rest is why.
I had written a reply contradicting post #63 and deleted it. Here is what survived.
Container choice matters: the material of the vial, the rubber closure, the fill volume all affect how quickly the contents degrade. Smaller fill volumes lose less to adsorption. Glass vials lose less to leaching than plastics.
Protecting from light: amber vials or opaque containers reduce light exposure. If you are storing for long periods and light matters, this is worth doing. For short-term prepared solutions, ordinary storage away from direct sunlight is usually adequate.
Post #67 answers the question as asked. The question underneath it is different.
My experience of Storing lyophilised material long term contradicts the reply above. I am posting it as a data point rather than as a refutation, because one person's experience is exactly that.
Lyophilised material is far more stable than the same material in solution. That is why suppliers ship it dry, and it is the reason to reconstitute only what will be used.
The reasoning is more useful than the number, which is why I have shown it.
Storing lyophilised material long term sits at the boundary between what this community can usefully discuss and what it cannot, and I think it falls on the discussable side, narrowly.
Post #74 is right about the mechanism and I think understates the practical bit.
An update on my earlier Storing lyophilised material long term post: the pattern held for another six weeks and then stopped, which I did not predict and cannot explain.
Coming back to post #72, because the follow-up matters more than the original answer.
Clarity is a weak test. A solution can lose a significant fraction of its active content to degradation or adsorption while remaining perfectly clear.
The strongest argument against my own position on Storing lyophilised material long term, stated as well as I can state it, since nobody else has yet.
Dry storage in a freezer is generally more protective than a refrigerator for long periods, provided the material is genuinely dry and the container genuinely sealed. Condensation on removal is the trap.
I would put a moderate confidence on that and no more.
Collapsed as off-topic by two members at trust level 3 or above
Adding a null result on Storing lyophilised material long term. I looked, carefully, and found nothing, and null results deserve posting precisely because they never are.
Small methodological point on Storing lyophilised material long term: repeating a measurement is cheap and resolves most of what is being argued about here at no cost to anyone.
Post #81 describes the usual case. This is about the unusual one.
Temperature excursions: if a vial sat at room temperature for a time, the question is whether the excursion was long enough to cause damage. Hours at room temperature is usually low risk. Days to weeks raises the risk. If you are unsure, contacting the supplier is more informative than guessing.
I checked the source rather than the summary, and they differ.
Adding the measurement that post #81 says would settle it.
The two questions that get merged here are whether material is degraded and whether it is contaminated. Storage affects both and they need different answers and different tests.
That is the honest state of it as of this week.
If you are going to test stored material, test it against a sample of the same lot stored properly rather than against the certificate. Otherwise you are measuring the difference between two laboratories as well.
Post #85 is the version of this I will quote in future. One addition.
Storing lyophilised material long term: I have looked for the primary source twice and failed twice. Either it does not exist or it is somewhere I do not know to look, and I would like to know which.
Collapsed as off-topic by two members at trust level 3 or above
Noted, and I have changed what I was going to do on the strength of it.
The two questions that get merged here are whether material is degraded and whether it is contaminated. Storage affects both and they need different answers and different tests.
I would put the burden of proof on the interesting explanation, not the dull one.
I read post #85 twice before replying, because I had assumed the opposite.
What I want from this Storing lyophilised material long term thread is the list of things that would need to be true for the claim to hold. If we can write that list, we can check it.
Reconstituted material carried in a bag for a day is a temperature excursion even in a cool climate. Where that matters is cumulative exposure over weeks rather than a single afternoon.
I would be glad to be shown a cleaner way of putting this.