Research guide · 2026

How to read a peptide COA

A field-by-field walk-through of a certificate of analysis, what each field tells you, how our lab rule scores it, and the red flags worth checking. Research use only; nothing here is medical advice.

Reviewed by the Peptide Source Review teamLast updated How we rate

Certificates on file
1,836

Certificates on file

Confirmed at the lab
83%

Confirmed at the lab

Labs with a lookup we used
22

Labs with a lookup we used

The fields on a certificate

Layouts differ between laboratories, but most peptide certificates carry the same ten fields. The specimen below is an illustrative layout with placeholder values, not a real report; the numbers match the explanations under it.

Example Analytical Laboratory · ISO/IEC 17025 cert. no. [number] Verify: [lab website]/verify · key [code]
Client:
[vendor name]
Sample / lot:
[sample ID] / [lot]
Received / tested:
[date] / [date]
Product:
[peptide], [label amount]
Identity:
LC-MS, observed mass matches
Purity (HPLC):
[measured %]
Content:
[measured amount] per vial
Endotoxin (LAL):
[result] EU/mg
Sterility / heavy metals:
[pass or fail] / [result]
Illustrative layout only. Bracketed values are placeholders.

Field by field

  1. Laboratory name and accreditation

    Look for: The issuing laboratory's full name, address and, if it holds one, an ISO/IEC 17025 accreditation with the accrediting body and certificate number.

    Why it matters: The name is what you look up. A report is only as good as the laboratory behind it, and accreditation means an outside body audits its methods.

    How PSR scores it: A certificate from a directory laboratory at tier B- or better earns +2; an accreditation active on the accrediting body's register on the test date adds +1. A laboratory whose independence is not established (tier D) scores a flat 2.0 (rule A3). See the lab directory.

  2. Client name

    Look for: The business that sent the sample in. It should be the vendor whose page shows the certificate.

    Why it matters: A report issued to a different business describes that business's sample, not necessarily the vial you are looking at.

    How PSR scores it: Certificates issued to another business carry the SUPPLIER adjustment (up to −0.5). A posted copy whose client differs from the laboratory's own record scores 0 (rule A4).

  3. Sample ID and lot number

    Look for: A sample or report ID from the laboratory and the vendor's lot or batch number.

    Why it matters: The lot is what ties the report to a specific batch. Without it you cannot match the certificate to your vial.

    How PSR scores it: A missing lot is not deducted by itself, but one lot label printed on certificates for different compounds carries the LOT adjustment (−0.2).

  4. Test date

    Look for: The date the laboratory received or tested the sample.

    Why it matters: An old report may describe stock that has long since sold out.

    How PSR scores it: The date drives rule A6: each scored certificate more than 12 months old takes 0.25 of its score off the lab sub-score, weighted by the number of products. An undated certificate counts as older than 12 months.

  5. Identity method

    Look for: How the laboratory confirmed the compound is what the label says: mass spectrometry (MS, LC-MS) or HPLC retention time.

    Why it matters: Mass spectrometry measures the molecule itself. A retention time only shows that something came off the column where a reference did, which another compound can also do.

    How PSR scores it: A laboratory whose reports identify by retention time alone passes check L4 only partly, which caps it at tier B+ in our lab grading.

  6. Purity (%)

    Look for: A measured HPLC purity figure, such as 99.4%, not just a specification like "≥98%".

    Why it matters: Purity is the share of the sample that is the target peptide. The rest is something else.

    How PSR scores it: Purity of 99.7% or higher adds +0.5; 99.0% up to but not including 99.7% adds nothing; 97.0% up to but not including 99.0% takes -1.5; below 97.0% takes -3. A specification with no measured figure gets no purity adjustment either way.

  7. Quantity or content per vial

    Look for: The measured amount of peptide in the vial (net content), compared with the label.

    Why it matters: A vial can be pure but under-filled. Quantity tells you how much is actually there.

    How PSR scores it: No points are awarded for it, but a posted copy whose quantity differs from the laboratory's record scores 0 (rule A4).

  8. Endotoxin

    Look for: A bacterial endotoxin result (usually LAL), with units and a limit.

    Why it matters: Endotoxins are residues from bacteria that purity testing does not detect.

    How PSR scores it: An endotoxin test adds +0.5, including from a separate endotoxin report for the same product within 12 months. 703 of the 1,836 certificates we hold (38%) include one.

  9. Sterility and heavy metals

    Look for: A sterility result (USP <71> or a PCR or rapid sterility screen) and, sometimes, a heavy metals panel.

    Why it matters: Sterility tests look for live microorganisms; heavy metals panels look for contamination from manufacturing.

    How PSR scores it: Sterility adds +0.5 (281 certificates, 15%). Heavy metals earn no points, and a heavy-metals-only report is not counted as a certificate of identity or purity (rule A2b).

  10. Verification key or portal

    Look for: A code, QR code or link that opens the laboratory's own copy of the report on the laboratory's own website.

    Why it matters: This is the only field that lets you check the report with someone other than the seller.

    How PSR scores it: A printed key adds +1.5; confirming it at the laboratory adds another +1.5. A key we cannot find at the laboratory keeps its +1.5 and earns nothing more (rule A5). The testing gate (A9) only counts confirmed certificates.

A certificate starts at 3 points for being published, and the items above take it up to a maximum of 10. The full rule, with worked examples, is on How we rate.

Red flags

  • The client name is a different business

    The report was ordered by someone else. Ask whose sample it was. 18 listed vendors currently carry the SUPPLIER adjustment for this.

  • Identity by retention time only

    Without mass spectrometry the report shows the sample behaved like the reference, not that it is the reference compound.

  • No lot number

    Nothing ties the report to the batch being sold. 28 vendors carry the LOT adjustment for reusing one lot label across different compounds.

  • Older than 12 months

    The batch tested may be gone. 92 scored certificates across our listings are more than 12 months old or undated.

  • Not found at the laboratory's own portal

    If the lab's lookup has no record of the code, the copy you were shown cannot be confirmed. Check the code exactly as printed and try the control below before concluding anything; we record 26 scored certificates whose key was not found.

  • The same analysis on several vendors' pages

    One report (same sample ID, date and results) shown by different sellers describes one sample. If the lab's record names a different client, the posted copy scores 0 under rule A4.

How often we have found each of these, with how to check them yourself: how to spot a fake peptide COA.

Check it with the laboratory

Of the 1,836 certificates on file for 93 listed vendors, 1,711 print a verification key and 1,521 (83%) were confirmed against the issuing laboratory's own record. Always open the lookup on the laboratory's own domain rather than a link from the seller, compare every field with the vendor's copy, and run the control: change one character of the code and confirm that the lookup now returns nothing.

Step-by-step guides for each laboratory we have confirmed certificates with:

Reading a COA: Frequently Asked Questions

What is a peptide certificate of analysis (COA)?

A COA is a laboratory report on one sample of a peptide. It usually states the laboratory, the client who sent the sample, a sample or lot number, the test date, how identity was confirmed, the measured purity and content, and sometimes endotoxin and sterility results.

How do I check that a peptide COA is real?

Use the verification key, code or QR code printed on the certificate at the laboratory's own website, not at a link the seller provides. A genuine code returns the laboratory's own copy, which should match the vendor's copy. As a control, change one character of the code: a working lookup should then return nothing.

Is HPLC enough to confirm a peptide's identity?

HPLC measures purity well, but identity by HPLC retention time alone is weaker evidence than mass spectrometry, because a different compound can elute at a similar time. Peptide Source Review grades a laboratory that identifies by retention time only no higher than tier B+.

How old can a COA be?

Peptide Source Review treats a certificate more than 12 months old, or with no date at all, as aged: it still counts, but a quarter of its weight comes off the vendor's lab sub-score (rule A6). A newer certificate is more likely to describe current stock.

How many certificates has Peptide Source Review confirmed at the issuing laboratory?

Of the 1,836 certificates currently on file for listed vendors, 1,521 (83%) were confirmed against the issuing laboratory's own record, and 1,711 print a verification key.

Does a COA say anything about using a peptide?

No. A certificate describes the identity, purity and contents of a tested research sample. It is not evidence of safety or effect in people, and the products discussed on this site are sold for laboratory research use only.

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Peptide Source Review covers research peptides: substances sold for laboratory and research purposes, not for human consumption. By continuing, you confirm that you are at least 18 years old and that nothing on this site is medical or legal advice.

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