Storing lyophilized reference materials

Storage conditions and lot stability data are stated on each certificate of analysis. That line is the instruction; everything in this post is the reasoning behind it. If the certificate says one thing and a general guide says another, the certificate wins — it was written about your lot. If you do not have the certificate for a lot you hold, contact support with the lot number and it will be sent the same business day. See how to read a certificate of analysis.

Lyophilized material is stable because it is dry, sealed and dark. Storage is about keeping it that way. Four factors work against it:

• Heat. Chemical degradation is faster at higher temperatures. Cooler storage slows it; that is the whole logic of refrigerated and frozen storage.
• Light. Some molecular groups absorb light and react. Keeping the vial in its packaging, or in an opaque box, removes the driver.
• Moisture. A lyophilized cake is porous and will take up water from the air if the seal is compromised. Water reintroduces the chemistry that drying removed.
• Temperature cycling. Moving a vial repeatedly between cold and room temperature causes condensation on and around it each time. One cycle is trivial; dozens are not.

None of this requires special equipment. It requires consistency:

• Keep the seal intact until the material is needed. An unopened vial is a dry vial.
• Store at the condition stated on the certificate, in the dark, and leave it there. Do not pull the vial out to look at it.
• If a vial must come out of cold storage, let it reach room temperature before opening so condensation forms on the outside of the glass, not inside.
• Label the storage location in your inventory so the vial is retrieved once, not hunted for. See inventory and labeling.

The material is shelf-stable in transit and ships without a cold chain: a sealed, dry, dark vial tolerates a few days at ambient temperature by design. That is a statement about transit, and it should not be read as "room temperature indefinitely." Once the parcel arrives, storage begins, and the certificate governs. We explain the distinction in does research material need a cold chain?.

Storage discipline also has a paperwork consequence. Material that has been stored outside the conditions stated on its certificate is not eligible for return, and neither is material whose seal has been broken — see the returns policy. Keeping the vial sealed and stored as stated protects the material and preserves your options.

Storage discipline fails most often through disorganisation rather than through the wrong temperature. A freezer or refrigerator where vials are loose, unlabelled and hunted for is one where the door stays open, vials are handled repeatedly, and the wrong lot gets picked up. A simple system fixes it: one labelled box or rack per supplier or per project, vials in their original packaging, an inventory sheet that names the box and position for each lot number, and a rule that the inventory is updated before the door closes. Retrieval then takes seconds, once. That system is also what makes a receiving check meaningful, because the vial goes from the receiving bench to a recorded place — see inspecting a vial on arrival. The quality page states the standard the material arrives in; the storage system is what preserves it.

This is general laboratory practice for keeping a lyophilized solid in the condition its certificate describes. It is not a preparation, dilution or usage instruction, and we publish none. All material is supplied for in-vitro laboratory research only; handling is the responsibility of the qualified researcher. See research use only.