Storage and stability

Two states, two completely different problems

Almost every argument about storage dissolves once you separate these.

Lyophilised powder is dry, and the dominant degradation routes for peptides — hydrolysis, deamidation, aggregation — all need water to proceed at any speed. A sealed dry vial is a fairly robust object. It survives a courier van. It survives a warm afternoon. It does not enjoy months at 30°C, but a few days of transit heat is not the catastrophe the packaging theatre implies.

Reconstituted solution is the opposite. The peptide is now in water at a low concentration, in contact with a rubber stopper and a headspace of air, being punctured weekly. This is where time and temperature genuinely cost you, and it is the state almost nobody worries about because it is at home rather than in transit.

Storage reference

These are the conventions this community has converged on, not manufacturer specifications for any particular product. Where a manufacturer publishes a figure for a licensed product, that figure wins.

Your fridge is not one temperature

This is the single most useful thing on this page. A domestic fridge has a temperature gradient, and the door is the worst place in it: it is warmest, it cycles every time the fridge is opened, and it is mechanically the most disturbed shelf you own.

Members who have logged their own fridges consistently report several degrees between the back of the middle shelf and the door bin — one commonly cited pair of readings is around 2°C at the back and near 8°C in the door of the same appliance. Put a cheap thermometer in yours and find out. Then store at the back, and never in the door.

Excursions: time at temperature, not "it got warm"

A temperature excursion is not an event, it is an integral. Six hours at 15°C and six hours at 32°C are not the same exposure, and neither is comparable between dry powder and solution. This is why c/coldchain asks for a logger trace and removes "the box felt warm" as evidence — the second statement contains no information.

A cheap USB data logger costs less than a vial and settles arguments in seconds. Drop it in the box on an order, get a CSV back, and you will know both what your lane actually does and how much of the worry was justified. Several members will lend one out.

Reading a trace

• Peak temperature matters less than total time above 8°C, and both matter less for powder than for solution.
• A gel pack that arrives fully liquid tells you the pack was exhausted, not that the contents cooked. Packs exhaust in the first day of a five-day trip by design.
• The last leg is often the worst — a local delivery van on a summer afternoon frequently registers the highest reading of the whole journey.
• Photograph the packaging at unboxing, before you unpack it. That photo is the only evidence that will ever exist and you get one chance at it.

What good packaging actually is

Insulation plus thermal mass. A foam envelope with a single small gel pack rattling around inside has neither in any useful quantity — the pack has no mass to hold the temperature and the envelope has no insulation to slow the ingress. A proper cold box has a snug void, enough frozen mass for the expected transit, and the vials held away from direct contact with the coolant.

Vendor packaging quality is tracked per-supplier on the source pages because it varies enormously and, unlike purity, it is something you can assess yourself on arrival with no laboratory involved.

Light, air, and adsorption

• Light. Matters for some compounds more than others and is rarely tabulated properly. The mitigation is free: keep vials in the box or the carton. There is no reason to store anything in bright light.
• Air and headspace. Every puncture exchanges a little air. This is part of why in-use windows exist and why a vial you have drawn from twenty times is not the same object as one you have drawn from twice.
• Adsorption. At very low concentrations a small amount of peptide sticks to glass and to the stopper. It is a real loss and it is proportionally larger for dilute solutions in large vials, which is a mild argument against reconstituting at an absurdly high volume.

When to bin it

The honest list is short.

• Cloudy or particulate after it has had time to dissolve. Discard. This is not a judgement call.
• Visible colour change. Discard.
• Foam that will not settle, from a vial that was shaken hard. Denatured protein does not un-denature.
• Reconstituted and left at room temperature far beyond its window. Discard, and stop trying to argue yourself into it — the sunk-cost reasoning in these threads is remarkably consistent and remarkably bad.
• A dry vial that got warm in transit. Almost certainly fine. Test it if the value matters to you; do not bin it on a feeling.

Things that are repeated and are not true

• "If the ice pack melted the product is ruined." No. See the two-states section.
• "Freezing extends the life of a reconstituted vial." No — freeze-thaw is one of the more reliable ways to aggregate a peptide in solution.
• "Sterile water is fine, it is basically the same." No. No preservative means no in-use window.
• "28 days is a hard biological limit." No, it is a preservative convention. It is a good rule and it is not physics.
• "Cold shipping is a scam because the powder is stable." Also no. The packaging is there for the worst-case transit and for the reconstituted-on-arrival case, and the marginal cost of doing it properly is trivial.