Conditions: ecnoglutide · 37 °C · five days.
I want to decide this in advance so that I am not deciding it under pressure later.
Assume I will follow the plan I write down, so I would like it to be a good one.
What should I decide now, and what should I defer?
Five days at 37 °C is about 46 refrigerated days of equivalent exposure. 37 °C is 32 kelvin above the 5 °C middle of a 2–8 °C refrigerator. The ten-degree rule of thumb — degradation rate roughly doubling per 10 K — makes that about 9.2 times the refrigerated rate, which is an order-of-magnitude statement and not a shelf life. At 46 equivalent days a test is more likely to reassure you than to tell you something, which is a legitimate reason to run it and a poor reason to expect a finding. Either way, record the five days and the temperature now, while you still know them; an excursion you did not write down is an excursion you cannot interpret later.
Answering this needs the transit duration and the ambient temperature, and then the arithmetic is straightforward.
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.
| State | Condition | Usable window | Basis |
|---|---|---|---|
| Lyophilised solid | −20 °C, sealed, dry | 24–36 months | Supplier guidance |
| Lyophilised solid | 2–8 °C, sealed | 12–24 months | Supplier guidance |
| Lyophilised solid | 25 °C, sealed | 4–8 weeks | Extrapolated (Arrhenius) |
| Lyophilised solid | 40 °C, sealed | 1–2 weeks | Extrapolated |
| Solution, preserved | 2–8 °C | 28 days | USP microbiological convention |
| Solution, preserved | 25 °C | 3–7 days | Extrapolated |
| Solution, unpreserved | 2–8 °C | 24 hours | USP microbiological convention |
Windows for the solid state are chemical; windows for solution are microbiological and usually shorter than the chemical limit.
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.
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.
Analytical standards and reagents with traceable certificates. Every quantitative result you read inherits the accuracy of the standard behind it.
Shop standardsThe 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 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.
To be exact about it, 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.
Lyophilised tolerates the lane. That is the answer for almost every order.
edited 23 Feb 2025 by deamidation_watch — added the method parameters
Start with the physical state, because it changes the answer completely and is the first thing to establish.
Anything shipped in solution is a different risk category, because hydrolysis and deamidation proceed in the aqueous phase and are strongly temperature-dependent.
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.
Single-use temperature loggers are standard practice in supply chains where temperature genuinely matters and are inexpensive at parcel scale.
A liquefied pack is expected. It is not evidence of a problem.
The underlying point is that the domestic leg after arrival is the part most often left in a warm hallway and least often worried about.
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.
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.
The relevant detail is that 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.
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.
Buy a logger if you actually want to know. Everything else is inference.
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.