How to Read a Certificate of Analysis (COA) for Research Peptides
Last updated October 6, 2026
A Certificate of Analysis, or COA, is the lab record attached to a research compound. It answers a deceptively simple question: what was in the sample that was tested, and how much of it? This guide walks through a COA field by field, so a rigorous analytical record can be told apart from a marketing graphic.
What a COA actually is
A COA is a document issued by an analytical laboratory that reports the test results for one specific lot of material. The phrase “one specific lot” is the part people miss. A COA is not a statement about a product line in general; it describes the particular production run identified by its lot or batch code. A different run of the same compound isn't described by it, because purity and contaminant levels vary between runs.
Because it is a research analytical record, a COA reports chemistry: identity, purity, and contaminants. It does not make any claim about how a compound performs, what it does in a living system, or whether it is appropriate for any use beyond in-vitro research. That frame applies to every field below.
The header: lab, lot, and date
Start at the top. A complete header establishes accountability and traceability; a COA missing these fields is hard to rely on before a single result has been read.
| Field | What it tells you |
|---|---|
| Testing laboratory | Who ran the analysis. A named, contactable lab can be checked with; a blank or generic label cannot. |
| Lot / batch code | Ties the result to one production run — a printed number or, for some vendors, a cap and seal colour. The certificate describes a vial only when the vial carries the same lot. |
| Test date | When the analysis was performed. The results describe the sample as it was on that date. |
| Compound + method | The analyte tested and the techniques used, typically HPLC for purity and mass spectrometry for identity. |
Identity confirmation
Identity answers the question: is this the molecule it claims to be? The standard tool is mass spectrometry, which measures the molecular weight of the compound and compares it to the theoretical mass of the target peptide. When the observed mass matches the expected mass, identity is confirmed. A purity number is meaningless if the identity is wrong, which is why a serious COA always reports both. For a deeper look at the two techniques, see HPLC vs mass spec.
Purity percentage
Purity is usually derived from HPLC (high-performance liquid chromatography). The instrument separates the sample into its components and measures the area of the peak attributable to the target compound as a percentage of the total. A result of 98% means the target peak accounts for 98% of the detected material, with the remaining 2% being related impurities such as truncated or modified sequences.
Purity is powerful but narrow. It does not by itself tell you the identity, the net peptide content by mass, or the contaminant load, and it is a record of the one lot that was tested rather than a property of the compound.
Contaminant screens
Beyond identity and purity, a thorough COA reports screens for contaminants that purity alone will not surface:
- Endotoxin: bacterial residues detected by the LAL assay.
- Heavy metals: elements such as lead or arsenic, measured by ICP-MS.
- Residual solvents / counter-ions: leftovers from synthesis, such as TFA.
- Water content: moisture in a lyophilized powder, which affects net mass.
Each is a separate assay, and a purity figure says nothing about any of them.
The overall result
Many COAs end with an overall pass or fail against the lab's specification. Read it as a summary, not a substitute for the underlying numbers. A “pass” with no visible purity figure, no method, and no lot code is worth less than a plain table that shows its work.
Confirming a COA is genuine
A COA is only as good as its provenance
Four checks help. First, confirm the certificate names a lot, and compare it with the lot on the kit: a certificate describes only the lot it names, so a different lot means it doesn't describe that vial — where vendors restock continuously, that is expected rather than a sign of a fake. Second, confirm the lab is named and contactable. Third, prefer a COA that includes the raw chromatogram and spectrum over a tidy summary image, which is easy to fabricate. Fourth, where the lab offers it, compare the certificate with the lab's own copy, and weigh who commissioned the test, as covered in third-party vs vendor testing.
On Peptuvia, lab results are published, pass or fail, in the COA library. Each COA covers only the lot it names, and we don't test every batch. Vendors ship thousands of kits and restock continuously, so there's no guarantee your order will come from the tested lot. To check a specific lot, see how to look up a peptide COA by batch code; the labs whose certificates we publish are listed on the testing page.
Frequently asked questions
What is a Certificate of Analysis (COA)?
A Certificate of Analysis is a document issued by a laboratory that reports the analytical test results for one specific lot of material — typically identity, purity, and contaminant screens — tied to a lot or batch code.
What should a peptide COA include?
A complete peptide COA names the testing laboratory, a lot or batch code, the test date, the analytical methods used (such as HPLC and mass spectrometry), a purity percentage, an identity confirmation, and where relevant, contaminant results such as endotoxin and heavy metals.
What doesn't a COA tell you?
A COA is an analytical record of what one sample contained when it was tested. It describes no lot but the one it names, it says nothing about how a compound behaves in any use, and it does not authorize human or animal use: research-use-only material is for in-vitro laboratory study.
How do I confirm a COA is real?
Check that it names its lot, a laboratory that can be contacted, the test date and the methods; prefer raw chromatogram data over a summary image; and, where the lab offers it, compare the certificate with the lab's own copy. If the lot on a vial differs from the lot on the certificate, the certificate doesn't describe that vial — where vendors restock continuously, that is expected rather than a sign of a fake.
For Research Use Only. All products are sold as research chemicals for in-vitro laboratory study. Not for human consumption, medical, veterinary, or household use.