The lot number is the smallest thing printed on a research peptide vial, and the most important. It is the only link between the sealed vial in your hand and the test records that describe it. If that link is broken, the certificate of analysis (COA) describes some other material.
The right time to check it is before the seal is broken. Once a vial is opened, returning it or questioning it gets much harder. This guide gives a step-by-step routine for verifying a lot number on arrival, explains what a matching record should show, and lists the warning signs that mean you should stop and ask questions first.
What a lot number is
A lot (or batch) is a quantity of material made in one production run under the same conditions. Every vial filled from that run shares a lot number. Tests are run on samples from the lot, and the findings apply to every vial in it.
That's the whole logic of lot-level testing. It only works if:
- the lot number is printed on the vial;
- the same number appears on the test record;
- the record is genuinely for that lot, not a generic or reused document.
Why it's worth checking every time
Control laboratories that test peptide products bought online have documented the kinds of failures lot verification is designed to catch.
- Wrong amount. A Danish study of peptide vials from three online shops, each labeled 10 mg, measured 4.32 to 8.84 mg per vial (Breindahl et al., 2015; DOI: 10.1002/dta.1655).
- Low purity and contaminants. Belgium's Scientific Institute of Public Health found high variation in peptide amount, purities as low as 5–75% for cysteine-containing peptides, and arsenic and lead in falsified peptide products (Janvier et al., Talanta, 2018; DOI: 10.1016/j.talanta.2018.06.023).
In each case, the only way to know was analysis tied to the material. A verified lot number is how you connect your vial to that analysis.
The routine: seven steps before you break the seal
Step 1: Find the lot number on the vial itself
Look on the vial label, not just the outer box or the packing slip. Boxes and slips can be swapped. The vial travels with the material. Note the number exactly, including letters, dashes and leading zeros.
Step 2: Check it matches the box and your order
The vial, the carton and the packing slip should all show the same lot number, compound and strength. A mismatch doesn't prove a problem, but it's the first question to ask the supplier.
Step 3: Find the record for that exact lot
Use the supplier's lookup page or the COA provided. The best setups let you type the lot number into a public page and get the record directly: no login, no emailing a sales address. A record you can reach yourself, with a permanent link, is one you and your colleagues can all check.
Step 4: Match the details field by field
Compare the record with the vial:
| Field | Vial | Record | Match? |
|---|---|---|---|
| Lot number | |||
| Compound name | |||
| Strength | |||
| Form (e.g. lyophilized powder) | |||
| Storage condition |
Every field should match exactly. "Close" isn't a match.
Step 5: Check the record contains real evidence
A lot record worth trusting shows:
- Identity by mass spectrometry: theoretical vs. observed mass, with the spectrum.
- Purity by HPLC: the measured value next to its specification, with the chromatogram.
- Endotoxin value against a limit, if tested.
- The testing laboratory by name, and the test date.
A record with typed numbers and no traces, or no laboratory name, is weaker evidence. Our guide to HPLC vs mass spectrometry explains what each trace proves. Related reading: HPLC vs Mass Spectrometry: What Each Test on a Peptide COA Actually Proves.
Step 6: Inspect the sealed vial
Without opening it, check that:
- the seal and cap are intact and untampered;
- the label is printed, not handwritten, and readable;
- the freeze-dried cake looks dry and intact, not collapsed, melted, sticky or discolored, and matches the appearance described on the record.
Step 7: Log it
Record the lot number, compound, date received, condition on arrival, and where the record lives (save the link or file a copy). Store the vial at its labeled condition straight away. If anyone ever questions an experiment, this entry lets you show exactly which material was used and what its record said.
Warning signs: stop and ask before opening
- No lot number on the vial.
- A lot number that doesn't return a record, or returns a record for a different compound or strength.
- The same COA used for several different lots.
- A record with no laboratory name or no test date.
- A test date that falls after you received the vial, or years before the lot could have been made.
- A record available only "on request."
- A damaged seal or a collapsed or discolored cake.
If you see any of these, keep the vial sealed and contact the supplier with photos and the lot number. A sealed vial is much easier to question, return or send for independent testing than an opened one.
Reading the lot number format
Lot numbers aren't standardized across the industry, but most encode something useful. Common patterns include:
- A prefix identifying the supplier or product line;
- A date element, such as a year and month or a sequential production number;
- A suffix distinguishing sub-batches or fill runs.
You don't need to decode a supplier's format to verify a lot. You only need the number on the vial to match the number on the record exactly. But if a supplier's lot numbers look random, never change from order to order, or are identical across different compounds, that's worth asking about. A lot number that never changes isn't tracking lots.
Keeping a lot log your whole team can use
A shared log turns individual checks into a lab habit. A simple spreadsheet works, with one row per vial:
| Column | Example entry |
|---|---|
| Date received | 2026-10-02 |
| Supplier | (name) |
| Compound and strength | (as printed) |
| Lot number | (exactly as printed) |
| Record link or file | (URL or path) |
| Record matches vial? | Yes / No, with notes |
| Condition on arrival | Seal intact, cake dry and intact |
| Storage location | Fridge 2, shelf B |
| Opened on / by | (date, initials) |
When a question comes up months later, the answer is one row away.
For critical work: independent confirmation
A supplier's lot record is the starting point. For work where the identity or amount of material is critical, consider sending a sealed vial from the same lot to a contract laboratory for an identity check by LC-MS. Official control laboratories use exactly this approach: a validated LC-MS/MS method to identify peptides, followed by UHPLC to quantify them (Vanhee et al., Talanta, 2015; DOI: 10.1016/j.talanta.2015.04.022).
How Seratide's lot lookup works
Every Seratide vial is printed with a lot number in the format SRT-0000-XXX. Type it into the Lot lookup page and you get the record for that lot: compound, form and container; HPLC purity specification and measured value; identity by LC-MS; endotoxin; and the testing laboratory and date. No app, no login, and each record has a permanent link you can share.
To be plain about where things stand: the records on that page today are layout samples. They are clearly marked, show the format only, and carry placeholder values, not measurements. Issued laboratory reports replace them as each lot is analyzed. We'd rather say that than let a sample page pass for a real test report, and it's the same standard this guide asks you to apply to every supplier, including us.
Seratide is operated by Axe Cap Holdings LLC; more on our About page. Packing and tracking details are on our Shipping Policy.
Sources
All sources below were opened and their PubMed abstracts read on 2026-09-29. Claims are limited to what the abstracts state. (Source 1's title names the specific peptide studied; the article body deliberately does not.)
- Breindahl T, et al. Identification and characterization by LC-UV-MS/MS of melanotan II skin-tanning products sold illegally on the Internet. Drug Test Anal. 2015;7(2):164-72. PubMed: https://pubmed.ncbi.nlm.nih.gov/24771717/ · DOI: https://doi.org/10.1002/dta.1655
- Janvier S, et al. Impurity profiling of the most frequently encountered falsified polypeptide drugs on the Belgian market. Talanta. 2018;188:795-807. PubMed: https://pubmed.ncbi.nlm.nih.gov/30029448/ · DOI: https://doi.org/10.1016/j.talanta.2018.06.023
- Vanhee C, et al. Analysis of illegal peptide biopharmaceuticals frequently encountered by controlling agencies. Talanta. 2015;142:1-10. PubMed: https://pubmed.ncbi.nlm.nih.gov/26003685/ · DOI: https://doi.org/10.1016/j.talanta.2015.04.022
For laboratory research use only.