Storage and stability
A purity figure describes material at the moment it was analysed. Whether it still holds when you use it is decided by storage, and by four things in particular: water, temperature, freeze-thaw cycles and oxygen. Lyophilised material is robust because it is dry; reconstituted material is not, and its useful window is measured in days rather than months.
Conditions are published per compound on its own certificate rather than as a single house rule, because the right condition depends on the molecule. The categories below are the ones actually used across the 64 published certificates, read from those certificates when this page is built.
The conditions published on our certificates
Each compound carries its own values. Open a certificate on the lab results page for the exact figures that apply to your material.
| Condition | What it covers |
|---|---|
| Lyophilized | 2–8°C, unopened vial, 24 months |
| Long-term | 8 distinct values across the catalogue, set per compound |
| Short-term | 9 distinct values across the catalogue, set per compound |
| Reconstitution | 20 distinct values across the catalogue, set per compound |
| Reconstituted | 12 distinct values across the catalogue, set per compound |
| In solution | 3 distinct values across the catalogue, set per compound |
| After opening | 3 distinct values across the catalogue, set per compound |
| Freeze-thaw | Aliquot before freezing; repeated freeze-thaw drives aggregation |
| Handling | 21 distinct values across the catalogue, set per compound |
What actually degrades material
Water
A lyophilised peptide is stable largely because it is dry. Water enables hydrolysis of the peptide backbone and lets everything else proceed faster, which is why water content is a routine determination on the certificate rather than an optional extra. A vial opened straight from cold storage draws condensation onto the cake, so letting it reach room temperature before opening is the single cheapest thing anyone can do to protect material.
Temperature
Degradation rates rise steeply with temperature. Lyophilised material tolerates ambient shipping for the days it spends in transit; it does not tolerate being stored that way. Once in solution the tolerance narrows sharply and the useful window shortens from months to days.
Freeze-thaw cycles
Each freeze and thaw concentrates solutes at the ice boundary and puts the peptide through an interface that promotes aggregation. The damage accumulates, so it is the number of cycles that matters rather than the total time frozen. Aliquoting after reconstitution, so each portion is thawed once, avoids the problem entirely.
Light and oxygen
Methionine, cysteine and tryptophan residues oxidise on exposure to air and light. This is why oxidised forms show up as related substances on a chromatogram, and why vials are sealed and stored in the dark rather than left open on a bench between uses.
What a certificate cannot cover
The certificate reports what was measured on a sample of the source batch on the date of analysis. It cannot describe how a vial was handled after it left, and no record can. If material has been stored warm, thawed repeatedly, or left reconstituted for weeks, the published figure no longer describes it. That is not a caveat on the testing, it is a property of peptides.
Common questions
How should lyophilised research peptides be stored?
Cold, dark and sealed. The published conditions for each compound are on its own Certificate of Analysis, because the correct condition depends on the molecule rather than on a single house rule. In general, lyophilised material is stored frozen for the long term and is stable for the days it spends in ambient transit, which is why shipping does not require a cold chain but storage does.
Why does shipping at ambient temperature not ruin the peptide?
Because a dry, sealed, lyophilised solid is far more robust than the same peptide in solution. The degradation routes that matter all need water, and freeze-drying has removed it. The exposure that damages material is weeks or months at room temperature after arrival, not days in a parcel.
How long does a peptide last once reconstituted?
Much less time than as a solid, and the specific window is published per compound on its certificate. Once in solution the peptide is exposed to hydrolysis, oxidation and adsorption to container surfaces, none of which apply to the dry cake. Aliquoting into single-use portions immediately after reconstitution avoids repeated freeze-thaw cycles, which is usually the largest single loss.
Does a Certificate of Analysis guarantee purity after delivery?
No. The certificate reports what was measured on a sample of the source batch at the date of analysis. It says nothing about how the vial was handled after it left, and no record can. That is why the storage conditions are published alongside the analytical results rather than tucked into a footnote: the number on the certificate is only maintained if the material is kept the way the certificate assumes.
The rest of the evidence
Each page answers one part of the same question. None of them asks you to take a claim on trust.
The procedures that decide whether a batch is released, held or withdrawn.
Every technique on the certificates, what it proves, and what it cannot.
Field by field, plus the red flags that tell you a certificate is worthless.
How the vial in your hand connects back to the batch that was tested.
How material is made, how a supplier is qualified, and what changes trigger a re-test.
For research and laboratory use only. Handling guidance on this page concerns the storage of a research reference standard in a laboratory setting. Nothing here is medical advice, and these compounds are not for human or veterinary use.