- Document
- ST-08
- Section
- Storage fundamentals
- Revised
- Sources checked
- Bands
- −80 °C−20 °C
Long-Term Storage: Months to Years
Keeping peptide stock usable for months or years: why powder is the best long-term form, when to use −80 °C, inert-gas overlays, secondary containment and planned re-testing.
Bench card
- The most stable long-term form is sealed lyophilized powder, cold, dry and dark.
- −20 °C suits most powders; −80 °C is preferred for solutions and for oxidation-prone or archive material.
- Purge the headspace with dry nitrogen or argon before resealing oxidation-prone material.
- Use sealed secondary containment with desiccant, and keep a box map.
- Plan re-testing for material held beyond the supplier's stated period.
Long-term storage is about keeping a known material unchanged until it is needed, and being able to show that it was. The principles are straightforward: minimize water, oxygen, light and temperature, avoid disturbance, and keep records.
Keep it as powder
For storage measured in months or years, lyophilized powder is almost always better than a solution. Dissolve only what you need for the next block of experiments, and keep the reserve dry. If you must store solutions long term, freeze single-use aliquots at −80 °C.
Choosing −20 °C or −80 °C
| Material | Recommended band | Why |
|---|---|---|
| Sealed powder, most sequences | −20 °C | Chemistry is already very slow in the dry state |
| Sealed powder with Met, Cys or Trp, held for years | −20 °C or −80 °C | Extra margin against slow oxidation |
| Frozen solution aliquots | −80 °C | Unfrozen, concentrated pockets persist at −20 °C |
| Reference or archive material | −80 °C | Keeps comparisons valid across years |
Protect the headspace
Every opening replaces some of the vial’s dry headspace with humid, oxygen-rich room air. For oxidation-prone peptides, gently flushing the vial with dry nitrogen or argon before resealing reduces both. Argon is denser than air and settles over the solid, which some labs find makes it easier to use. Seal with fresh Parafilm or a new cap liner if the closure is worn.
Containment and organization
- Place vials in a sealed secondary container with desiccant and, ideally, a humidity indicator.
- Use opaque boxes for light-sensitive material.
- Keep a box map recording position, compound, lot, amount and date.
- Store in the body of the freezer, not the door, and away from the evaporator plate.
- Avoid frost-free freezers for anything frozen in solution.
How long is too long?
Suppliers sometimes state a shelf life or retest date. Beyond that date the material is not necessarily degraded, but its quality is no longer supported by data. For material held a long time, especially in solution, plan a re-test before critical use: an HPLC purity check against the original COA and a mass spectrum to confirm identity are usually enough. ICH Q1A(R2) uses the term retest period for exactly this idea.
Monitoring and back-up
Long-term storage is only as reliable as the equipment. Use continuous temperature monitoring with an alarm, agree what happens when a unit fails, and keep space in a second unit for emergencies. See Storage Equipment and Monitoring.
References
- Wang W. Lyophilization and development of solid protein pharmaceuticals. Int J Pharm. 2000;203(1–2):1–60. DOI
- Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. DOI
- Li S, Schöneich C, Borchardt RT. Chemical instability of protein pharmaceuticals: mechanisms of oxidation and strategies for stabilization. Biotechnol Bioeng. 1995;48(5):490–500. DOI
- ICH Q1A(R2). Stability Testing of New Drug Substances and Products. International Council for Harmonisation, 2003. ICH
- ICH Q5C. Quality of Biotechnological Products: Stability Testing of Biotechnological/Biological Products. International Council for Harmonisation, 1995. ICH
- USP General Chapter <1079> Good Storage and Distribution Practices for Drug Products. United States Pharmacopeia.