How to read a peptide COA: batch, purity and content
A certificate of analysis (COA) can help you assess a batch, provided you know which sample was tested and which tests were performed. Its value lies in its data and traceability, not the design of the PDF.
Quick answer: What makes a COA useful?
It should connect the product and batch you will receive to an identified sample, methods and verifiable results. Check identity, purity and content separately: an HPLC percentage does not establish sterility or the amount in each vial.
1. Connect the product, batch and sample
Start with the full product name and batch code. Check that they match the item requested. Identify who issued the report, when the analysis was performed and how the sample is described.
Ask whether the laboratory tested bulk material, a finished vial or a sample supplied by the vendor. These have different scopes. If the laboratory did not take part in selecting the sample, the report alone does not document that step in the chain.
2. Separate the analytical questions
Chromatography and mass spectrometry provide different information. Depending on the material and purpose, quality control may include identity, impurity profile, content or additional tests. A COA should let you distinguish the method, specification and result.
Do not interpret a percentage without knowing which measurement it refers to. Do not assume an unlisted test was performed.
Source: Bachem: quality control of peptides.
Purity, identity and quantity: what each test measures (Spanish)
3. Verify the document and its scope
If the analysis is presented as independent, request a verifiable report reference and check it through the laboratory's official channel. A screenshot or logo alone does not establish who issued a document.
Distinguish the measured result from an acceptance criterion. If the report says “complies”, look for the specification against which it was assessed. A result may be useful for one purpose without answering another question.
- Report number and issuing laboratory.
- Sample and batch identity.
- Method, date and result for each test.
- Limitations or conditions of the analysis.
4. Remember what the COA does not demonstrate
An analytical certificate does not establish clinical efficacy, a safe dose or authorisation as a medicine. If it does not include sterility or endotoxin tests, it provides no results for those measurements.
Before deciding, organise the questions that remain. Whether material is acceptable for an experiment depends on its specifications, the protocol and the actual scope of the available documentation.
Checklist: from vial to result
Imagine two files supplied for the same purchase. One shows a brand, “99%” and a name. The other identifies the batch, sample, date, report number and method for each result. The second lets you investigate what was measured and how it relates to the material; you must still verify it with the issuer and confirm that it corresponds to the batch delivered.
This is a teaching example, not a description of a Hexpeps batch or analysis. Use it to frame questions before ordering, not to declare a material approved.
| Item | What to look for | If missing |
|---|---|---|
| Product | Full name, form and stated quantity | Request the product specification |
| Batch and sample | Batch code and tested sample code | Link them to the vial and order |
| Issuer and date | Laboratory, report number and analysis date | Verify through an official laboratory channel |
| Methods | Test and unit for each result | Ask exactly what was measured |
| Results | Values, limits and acceptance criterion | Request missing pages or appendices |
How to verify a report without relying on a screenshot (Spanish)
What does testing one vial demonstrate?
A result applies to the sample examined. Extrapolating it to a batch requires information about sample selection, homogeneity and the control plan. A supplier sending a sample directly to a laboratory is a different route from randomly selecting a vial from the delivery received.
If you commission an independent test, keep the original identification, record which delivery the sample came from and agree the required quantity and tests with the laboratory. Do not replace the label or lose the link to the batch before analysis.
Frequently asked questions
Can I use a COA for another batch?
It can provide context about a product, but it does not document the result for the batch you would receive. Request the corresponding report.
Does a well-known laboratory guarantee the entire supply chain?
Not on its own. Also check how the sample was taken and sent, and how it is linked to the finished batch.
Does a QR code prove a COA is authentic?
It only helps if it leads to the issuer's official record and the details match. A QR code that returns to the shop or opens another PDF is not independent verification.
Can I request the report before paying?
You can request the report for the batch proposed for delivery and confirm its identity and scope. If no batch has been assigned yet, ask for that limitation to be made clear in the proposal.
Does a COA without a sterility test show that the vial is not sterile?
It shows that this property is not documented in the report reviewed. Without the relevant test, it establishes neither sterility nor contamination.
Sources consulted
These references informed this guide. They are not certificates for Hexpeps products or endorsements of our shop.
Conversations that help identify these questions
These are sources of questions, not medical evidence or verification of sellers. Our editorial policy (Spanish) explains the full selection and its limits.
- How can a COA be checked against the batch received rather than recycled documentation? (2026-04-13)
- Does testing one sample validate every vial and its subsequent stability? (2026-01-28)
- Which tests should a laboratory perform, and how do purity and identity differ? (2020-08-30)
- Does “third-party tested” include sterility, endotoxins and metals, or only HPLC? (2026-09-15)