What is the actual thermal profile of a Guangzhou to Europe lane in August?

I have continuous temperature data for the period in question, which is unusual and I would like to use it.

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.

What is the correct interpretation, and what is the common misreading?

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.

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.

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.

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.

More usefully, this is where the anxiety in this hobby is most out of proportion to the chemistry.

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.

A liquefied pack is expected. It is not evidence of a problem.

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.

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.

Anything shipped in solution is a different risk category, because hydrolysis and deamidation proceed in the aqueous phase and are strongly temperature-dependent.

Lyophilised tolerates the lane. That is the answer for almost every order.