Storage Temperature and Handling of Lyophilized Research Peptides (Dry Powder)

Lyophilized research peptides are stored as sealed dry powder at 2-8 °C (36-46 °F) on arrival, or at −20 °C (−4 °F) for long-term storage, protected from light and moisture; this is the Storage row printed on every Pepta Labs listing. The vials hold a dry solid made by freeze-drying (lyophilization) during manufacture, and they ship at ambient temperature. This page explains why a dry, hygroscopic solid is kept sealed, cold and dark, gives an anchored storage row for each listing it covers, and describes what a sealed vial should look like when it arrives.

What is a lyophilized peptide?

A lyophilized peptide is a peptide that has been freeze-dried: its solution is frozen, and the ice is then removed by sublimation under vacuum, which leaves the compound as a dry cake or loose powder inside the vial. The site glossary defines lyophilization the same way and adds that the dry form is the state in which the material is shipped and stored. For what a research peptide is and how Pepta Labs documents each listing, see what research peptides are.

The dry solid is not pure peptide. It holds three things: the peptide chain, the counter-ion that stays with the peptide after purification (usually trifluoroacetate or acetate), and residual water. The total mass of the solid is therefore greater than the net peptide mass. Pepta Labs does not report net peptide content per listing; TFA vs acetate salts explains the counter-ion share, and how net peptide content is determined covers the measurement.

What temperature are lyophilized peptides stored at?

The listing condition names two storage temperatures for the sealed vial: a refrigerator condition of 2-8 °C for the vial on arrival, and a freezer condition of −20 °C for long-term storage. Both apply to the dry powder in its sealed vial and to nothing else.

The listing condition does not name room temperature as a storage condition. Ambient temperature enters only while the sealed vial is in transit, and the listed condition applies from arrival. This page gives no storage period for the powder at any temperature.

Why is a lyophilized peptide kept sealed and away from moisture?

A lyophilized peptide salt is hygroscopic: the dry solid takes up water vapor from the surrounding air. Water taken up from the air raises the water content of the solid and its total mass, so each milligram of the solid then holds a smaller share of peptide. Water content in a solid is measured by Karl Fischer titration, a separate analysis from HPLC purity.

The stopper and seal of the vial are the barrier between the solid and room air, which is why the listing condition says to keep vials sealed. A vial moved from 2-8 °C or −20 °C into warmer room air collects condensation on the outside of the glass as it warms; an intact seal keeps that water outside the vial.

Why is a lyophilized peptide stored away from light?

Tryptophan and tyrosine residues absorb ultraviolet light, with absorbance maxima near 280 nm, and tryptophan, tyrosine, histidine, methionine and cysteine are the residues most often named as sites of photo-oxidation or oxidation. The table in the next section shows which listed compounds contain them, by position.

Each reaction changes the molecular mass by a fixed amount, which is how it shows up on a mass spectrum. Methionine oxidizes to methionine sulfoxide by adding one oxygen atom: +15.995 Da monoisotopic (about +16 Da). Tryptophan photo-oxidation gives N-formylkynurenine (+31.990 Da) and kynurenine (+3.995 Da). Two cysteine thiols joined as a disulfide lose two hydrogen atoms: −2.016 Da. These shifts are calculated from monoisotopic atomic masses; the expected mass table lists the calculated masses of each listed compound that the shifts are measured from.

What does each listing state about storing its sealed vial?

Every Pepta Labs listing states the same Storage row: refrigerate at 2-8 °C on arrival, or hold at −20 °C for long-term storage, and keep sealed vials away from light and moisture. The table below gives one row for each listing it covers, and each row’s anchor is the listing’s product slug, so a product page or guide can link straight to it.

The structure column is taken from the listing’s verified identity record. The last column names the residues from the light section above, by position, with the calculated mass shift a mass spectrum would show for each reaction. A dash means no verified identity record is published for that listing, so no residue note is given. “None of Trp, Tyr, His, Met or Cys” is a statement about the sequence, not about any vial. Listings not in this table carry the same Storage row on their product pages.

Every row above is also “sealed, away from light and moisture” on its listing. Appearance is not a column: where the analytical report for a compound states an appearance, that report is the reference, and the arrival section below explains how to read it.

How does the sealed dry powder ship?

Every Pepta Labs listing states: “Ships at ambient temperature with no cold pack and no insulated packaging. No cold chain is required for dry powder.” The listed storage condition applies from arrival.

Shipping is free within the United States, the only area served. “Most orders ship the next business day. Processing and delivery times are estimates, not guarantees.” The shipping terms give the full wording.

What should a sealed vial of lyophilized powder look like on arrival?

A sealed vial of lyophilized powder should arrive with the seal intact, the stopper seated in the neck, a label naming the compound and quantity, and a dry solid inside that may be a cake, a thin film on the glass, a small pellet or loose powder. Any of those forms is a dry lyophilized solid; transit can break a cake into loose powder or move it onto the walls and stopper.

Why does my peptide vial look empty?

A few milligrams of dry solid take up very little room. Ten milligrams is one hundredth of a gram, and a freeze-dried solid of that mass can sit as a thin layer on the base of the vial or cling to the glass as a film that is easy to miss. The quantity on the label is the supplier-stated nominal quantity, and vial fill-quantity testing is not claimed.

What colour is GHK-Cu powder, and what colour are other listings?

The reference for colour is the analytical report for that compound, not another vial. Two listed compounds have a colour in their identity records: the GHK-Cu copper(II) complex is a blue to blue-violet solid, while the copper-free tripeptide GHK is white, and NAD+ as the free acid is a hygroscopic white to off-white powder. The GHK-Cu guide covers the copper complex. Appearance is not an identity test: identity on the report is by mass spectrometry, and two different peptides can both be white solids.

Arrival check, step by step

1. Check that the seal is intact and the stopper is seated in the neck of the vial.
2. Check that the vial holds a dry solid: a cake, film, pellet or loose powder.
3. Read the label. “Vial labels identify the compound, quantity and research-use designation. They do not carry lot or batch numbers.”
4. Match the compound and quantity on the label to the order confirmation and to the listing.
5. Place the sealed vials at 2-8 °C, or at −20 °C for long-term storage, away from light.

For a vial that arrives with a broken seal, contact support@peptalabs.com (9 AM to 9 PM Pacific, seven days a week) before placing it in storage. “Unopened products in original sealed condition may be returned within 30 days of delivery with return authorization.” The returns terms give the process.

What does the analytical report say about the material over time?

Nothing after the date of analysis. The report records RP-HPLC purity and MS identity measured on a sample of one production run at the date of analysis; a report may also carry a storage-conditions field giving a recommended temperature, as the quality page lists, but it holds no measurement made after that date. The testing Pepta Labs represents is: “Independent third-party HPLC purity analysis and mass-spectrometry identity confirmation, commissioned through the purchasing group on a sampled production run from the source. Pepta Labs does not test in-house.”

Purity on the report is RP-HPLC area-percent, the main peak’s share of the total integrated peak area (HPLC purity explained). Identity is by mass spectrometry, an observed mass compared with the mass calculated from the formula (mass spectrometry identity). Reports are “Sent by email on request, before you order if you want to see it first.” Ask for one through the report request on the quality page.

Frequently asked questions

At what temperature are lyophilized peptides stored?

Sealed vials are refrigerated at 2-8 °C (36-46 °F) on arrival or held at −20 °C (−4 °F) for long-term storage, protected from light and moisture, which is the Storage row on every Pepta Labs listing.

What do the refrigerator and freezer terms in the listing condition mean?

The refrigerator condition is 2-8 °C (36-46 °F) and applies to the sealed vial on arrival; the freezer condition is −20 °C (−4 °F) and applies to long-term storage. The listing names no third condition.

Can lyophilized peptides be stored at room temperature?

The Pepta Labs listing condition does not name room temperature as a storage condition: it names 2-8 °C on arrival or −20 °C for long-term storage, sealed and away from light and moisture. The vials ship at ambient temperature without a cold pack, and the listing condition applies from arrival.

Why must the vial stay sealed?

Because a lyophilized peptide salt is hygroscopic, and water taken up from the air raises the solid’s water content and total mass, so each milligram then holds a smaller share of peptide.

Does the analytical report state how long the powder keeps?

No. The report records RP-HPLC purity and MS identity measured on a sample of one production run at the date of analysis and holds no measurement made after that date.

Why can a vial of a few mg look almost empty?

Ten milligrams is one hundredth of a gram, so a freeze-dried solid of that mass can sit as a thin layer or film on the glass that is easy to miss. The label quantity is the supplier-stated nominal quantity, and vial fill-quantity testing is not claimed.

What colour should the powder be?

The colour stated on the analytical report for that compound. Two identity records state a colour: blue to blue-violet for the GHK-Cu copper(II) complex, and white to off-white for NAD+. Colour is not an identity test; identity on the report is by mass spectrometry.

Sources

• Pepta Labs product pages, Physical form, Shipping and Storage rows, read on 2026-09-24.
• Pepta Labs Terms sections 6.2 (testing represented), 6.3 (report access), 6.4 (vial labeling), 8 (dispatch) and 9 (returns); the site glossary at /guide (lyophilization; lot numbers); product pages (free US shipping).
• PubChem compound records for the identity records in the per-listing table: CID 9941957 (BPC-157), 16132341 (TB-500), 16130571 (Thymosin Alpha-1), 165429100 (GHK-Cu), 125672 (KPV), 76283482 (SNAP-8), 124886 (glutathione), 5892 (NAD+), 16132413 (sermorelin), 16137828 (tesamorelin), 9831659 (ipamorelin), 71300630 (AOD-9604), 16197727 (Melanotan-I), 92432 (Melanotan-II), 9941379 (PT-141), 9811102 (Semax), 11765600 (Selank), 68816 (DSIP), 53314964 (VIP), 11764719 (SS-31), 146675088 (MOTS-c), 71300623 (thymulin) and 167312269 (FOXO4-DRI).
• Mass shifts: calculated from monoisotopic atomic masses (C 12.000000, H 1.0078250, N 14.0030740, O 15.9949146, S 31.9720707).

All products are supplied for laboratory research use only and are not for human or animal use.