A reference material that has been stored badly looks exactly like one that has not. Degradation is usually invisible, which is why storage is handled by procedure rather than by inspection.
Four things change a material
Temperature sets the rate of every chemical process involved. It is the dominant variable and the one most worth controlling.
Moisture restores the mobility and the reactant that freeze-drying removed. Even a dry solid picks up water from humid air once its seal is broken.
Light, particularly in the ultraviolet range, supplies enough energy to drive photo-oxidation. Aromatic residues are the usual targets.
Oxygen drives oxidation directly, most readily at methionine, cysteine and tryptophan.
Time is not a fifth factor so much as the multiplier on the other four.
Temperature is not a single number
A storage condition is a range with a duration attached, not a threshold that is either met or breached. What matters cumulatively is time spent at temperature, which is why a brief excursion during a courier handover is a different event from a fortnight in a warm room, even if the peak reading is the same.
This is also why "it arrived warm" is not on its own a verdict. What matters is how warm, for how long, and how the material is expected to respond. Record the excursion, and ask, rather than assuming either the best or the worst.
Freeze-thaw cycling deserves separate mention: repeatedly crossing the freezing point is more damaging than remaining at the higher of the two temperatures throughout. Storing material where it is stable and leaving it there beats moving it around.
Cold chain in transit and cold chain in storage
They are different problems.
Transit is a short, uncontrolled window managed with passive protection — insulated packaging and a coolant sized for an expected duration. It is designed for a journey of a certain length. A parcel held at customs beyond that length is outside what the packaging was specified for, however good the packaging is.
Storage is a long, controlled window managed with equipment and monitoring. The failure mode is not a bad day; it is a freezer that drifted for a month with nobody watching.
Moisture is the one that gets missed
Two habits matter more than any equipment.
Let a container reach room temperature before opening it. Cold glass in humid air condenses water onto and into the contents, which is a fast route to hydrating a material that was deliberately dried.
Keep desiccant with stored material, and keep the seal intact for as long as possible. Once opened, a container no longer has its original protection and its remaining life is shorter than the label implies.
Light
Amber glass, secondary packaging, or simply a dark storage space. The requirement is undramatic and easy to satisfy; it is usually missed by leaving material out on a bench rather than by any considered decision.
What to record
If material matters enough to store properly, it matters enough to record:
- the date received and the condition on arrival
- the storage location and its monitored temperature
- the date first opened
- any excursion, with its duration and peak
That record is what allows an unexpected result to be investigated instead of argued about.
What we do not provide
DC LABX does not supply dosing, reconstitution or administration guidance for any product, and does not represent any product as suitable for human or veterinary use. Everything above concerns keeping a material physically intact, which is a separate question from what may lawfully be done with it.