The specifics, since they change the answer: Changsha · Ireland.
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 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.
| Pathway | Dominant when | Detected by |
|---|---|---|
| Deamidation | Solution, neutral to alkaline pH | RP-HPLC, +1 Da on MS |
| Oxidation | Light, trace metals, peroxides | RP-HPLC, +16 Da on MS |
| Hydrolysis | Solution, extremes of pH | RP-HPLC, fragment masses |
| Aggregation | Agitation, interfaces, high concentration | SEC, visual haze; often invisible on RP-HPLC |
| Freeze-concentration damage | Freeze-thaw of buffered solution | SEC, loss of recovered content |
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.
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.
A cold pack tells you nothing about the eleven days before the last one.
Lyophilised tolerates the lane. That is the answer for almost every order.
Aggregated, published test results and vendor ratings built from submitted batches. Methodology stated, dataset browsable, no listing fees.
Browse resultsStart 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.
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.
Buy a logger if you actually want to know. Everything else is inference.
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.
Anything shipped in solution is a different risk category, because hydrolysis and deamidation proceed in the aqueous phase and are strongly temperature-dependent.
In practice, 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.
Arrhenius kinetics predict approximately a doubling of degradation rate per ten-degree rise and are the standard basis for cold-chain design.
Solutions are a different question and deserve the worry the solids get.
edited 23 Oct 2024 by ines_brandt — removed a claim I could not source
The domestic leg after arrival is the part most often left in a warm hallway and least often worried about.
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.
Single-use temperature loggers are standard practice in supply chains where temperature genuinely matters and are inexpensive at parcel scale.
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.
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.
A liquefied pack is expected. It is not evidence of a problem.
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.