I have continuous temperature data for the period in question, which is unusual and I would like to use it.
I would like to define my thresholds before I have a result, for obvious reasons.
I want a plan with explicit stopping rules, not just steps.
How do I make this decision on evidence rather than on feel?
Answer first: dry, cold, dark and still, with the lot code where you can still read it in a year.
Keep vials in their original carton or in an opaque box. Light exposure matters for tryptophan-containing sequences and for anything with a chromophore, and a closed box is free.
Position matters less than people think: upright or on its side makes no difference to a lyophilised powder, and upright is marginally better for a reconstituted vial because it keeps the stopper dry.
The 28-day in-use period for preservative-containing multi-dose preparations is printed on the diluent labelling and is a long-standing pharmacy convention.
The caveat is that storage conditions preserve what you have and cannot improve it.
Equilibrate before opening or you condense water into the cake.
Analytical standards and reagents with traceable certificates. Every quantitative result you read inherits the accuracy of the standard behind it.
Shop standardsThe relevant practical failure is not chemical at all: it is losing the link between a vial and its certificate when the box gets thrown away.
Label the vial at reconstitution with the date, the concentration and the resulting units per dose. This is the single most useful thirty seconds in the whole process.
Mechanically, let a refrigerated or frozen vial equilibrate to room temperature before opening, so humid air does not condense water onto a cold cake.
Nothing here is medical advice, and research-use compounds are not approved for human use.
Label the vial at reconstitution with date, concentration and units per dose.
edited 25 Feb 2025 by t_oyelaran — added the placebo-arm figures
The short version: powder in the freezer or fridge, reconstituted in the fridge for weeks, and never anything on a windowsill.
Store with the desiccant sachet if one was supplied, inside the secondary container rather than loose in a drawer. Residual moisture is the dominant variable in solid-state stability.
To be exact about it, reconstituted with a preservative-containing diluent: refrigerated, conventionally treated as usable for about 28 days from first entry. Without a preservative, single use and discard.
Photodegradation of tryptophan-containing peptides is documented and is the basis for light-protected storage recommendations.
A printed expiry on research-grade material has no stability programme behind it.
Dry, cold, dark, still. Four words and you have the answer.
Keep the paperwork with the material, or the material becomes anonymous.
Lyophilised powder: refrigerated at two to eight degrees for months, frozen at minus twenty for longer. The gain from minus eighty over minus twenty is small for a dry solid and is not usually worth the arrangement.
Two-to-eight-degree refrigeration and minus-twenty freezing are the standard storage conditions for lyophilised peptides in supplier documentation across the market.
Appearance does not indicate stability; a normal-looking cake can be substantially degraded.
Minus eighty buys very little over minus twenty for a dry solid.
Answering this needs the intended duration, since a fortnight and two years call for different arrangements.
Keep the certificate with the vial, physically or as a photograph filed under the lot code. A vial without a traceable certificate is an anonymous vial regardless of where it came from.
Residual moisture is the dominant determinant of solid-state stability, which is why desiccants accompany lyophilised material.
The caveat is that "within specification" and "unchanged" are different claims. A vial can lose a few per cent of content and still be usable for its purpose while no longer matching its certificate.
Keep the desiccant with the vial and the certificate with the lot code.
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.