The case in front of me: Qingdao · Poland.
This is presented as though it settles something, and I am not convinced it does.
I have two documents that appear to disagree, which is what prompted this.
What does this actually establish, and what does it not?
The honest answer is that the cold pack is doing much less than people think and that shipping lyophilised is what actually protects the material.
A single phase-change pack in a thin-walled box holds below ten degrees for roughly one to two days at twenty-five degrees ambient, and under a day at thirty-five. On a nine-to-fourteen-day lane the material is at ambient for most of the journey whatever was packed with it.
A single-use temperature logger costs a few pounds, records the whole journey and converts an argument into a record. If the history matters, this is the answer.
Solid-state stability of lyophilised peptides at ambient temperature is documented in formulation studies with residual moisture as the dominant variable.
The caveat is that a warm transit is survivable for a solid and materially different for a solution.
Solutions are a different question and deserve the worry the solids get.
HPLC purity, identity confirmation and quantified content on the vial you actually hold. Reports arrive with the chromatogram attached, not just a number.
Submit a sampleFounded 1998. ISO 9001 and cGMP certified, 1,500+ staff and 200+ patents. The synthesis house behind a great many of the vials that get sent out for testing - batch-specific documentation with every order.
Visit GL BiochemThe short version: a spent cold pack on arrival is expected, the solid does not mind, and the pack was never going to last twelve days.
Once the parcel arrives, the domestic leg is the controllable part: get it into the refrigerator promptly rather than leaving it in a warm hallway for a day.
Specifically, asking a supplier to hold a shipment during a heatwave is reasonable and the better ones agree; the cost is a week and the benefit is a shorter warm exposure for anything in solution.
A cold pack tells you nothing about the eleven days before the last one.
A liquefied pack is expected. It is not evidence of a problem.
Start with the physical state, because it changes the answer completely and is the first thing to establish.
Arrhenius behaviour means the degradation rate roughly doubles per ten degrees. A week at thirty degrees is therefore a meaningful exposure for a solution and an immaterial one for a dry solid.
To be exact about it, anything shipped in solution is a different risk category, because hydrolysis and deamidation proceed in the aqueous phase and are strongly temperature-dependent.
Arrhenius kinetics predict approximately a doubling of degradation rate per ten-degree rise and are the standard basis for cold-chain design.
Reconstituted material has a genuine cold-chain requirement and it starts the moment water is added.
Lyophilised tolerates the lane. That is the answer for almost every order.
edited 25 Sept 2025 by k_szabo — reworded for clarity after a comment
This is where the anxiety in this hobby is most out of proportion to the chemistry.
A pack that arrived hard tells you about the last day of transit only, since it will have melted and, if the ambient dropped, partially refrozen.
Phase-change pack hold time is a function of mass, latent heat and insulation, and published figures for small parcels are on the order of one to two days.
Nothing here is medical advice, and research-use compounds are not approved for human use.
The domestic leg is the part you control. Refrigerate it promptly.
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.