Conditions: Tianjin · Singapore.
I can parse the result. I am less sure what it licenses me to conclude.
I have deliberately not looked at anyone else’s interpretation yet.
Which parts of this are informative and which are decoration?
The relevant physics is latent heat: a phase-change pack holds temperature only while it is changing phase, and once it has melted it is a warm mass.
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.
More usefully, 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.
Lyophilised tolerates the lane. That is the answer for almost every order.
Analytical standards and reagents with traceable certificates. Every quantitative result you read inherits the accuracy of the standard behind it.
Shop standardsTo be exact about it, this is where the anxiety in this hobby is most out of proportion to the chemistry.
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.
That is the argument for shipping lyophilised rather than for shipping colder. A dry powder with low residual moisture is stable at ambient for months; the pathways that matter need water.
The caveat is that a warm transit is survivable for a solid and materially different for a solution.
Buy a logger if you actually want to know. Everything else is inference.
Worth being precise here: the domestic leg after arrival is the part most often left in a warm hallway and least often worried about.
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.
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.
Arrhenius kinetics predict approximately a doubling of degradation rate per ten-degree rise and are the standard basis for cold-chain design.
A liquefied pack is expected. It is not evidence of a problem.
edited 12 Apr 2026 by marta_okonkwo — corrected a unit error in the worked example
More usefully, if temperature history matters to you, buy a data logger. It is the only way to know.
Anything shipped in solution is a different risk category, because hydrolysis and deamidation proceed in the aqueous phase and are strongly temperature-dependent.
Reconstituted material has a genuine cold-chain requirement and it starts the moment water is added.
The domestic leg is the part you control. Refrigerate it promptly.
The 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.
Solid-state stability of lyophilised peptides at ambient temperature is documented in formulation studies with residual moisture as the dominant variable.
A cold pack tells you nothing about the eleven days before the last one.
Solutions are a different question and deserve the worry the solids get.
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.