I have continuous temperature data for the period in question, which is unusual and I would like to use it.
I have a result I cannot explain, and I would rather diagnose it than guess.
I have checked the obvious explanations and eliminated the two easiest ones.
What is the differential here, and which test discriminates between the options?
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 |
The part that matters: anything shipped in solution is a different risk category, because hydrolysis and deamidation proceed in the aqueous phase and are strongly temperature-dependent.
The caveat is that a warm transit is survivable for a solid and materially different for a solution.
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 resultsThe 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.
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.
Specifically, 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.
Reconstituted material has a genuine cold-chain requirement and it starts the moment water is added.
A liquefied pack is expected. It is not evidence of a problem.
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