How to read a peptide COA.

What a COA is

A Certificate of Analysis is a document issued by (or on behalf of) a manufacturer reporting the test results for a specific production batch. Its job is traceability: the batch number on the COA should match the batch number on the vial you hold.

Step 1: Match the report to the product

Before reading any results, confirm the document actually describes the vial in front of you:

1. Find the batch or lot number on your vial. It is usually printed on the label or etched on the glass.
2. Find the same number on the COA. A report with no batch number — or a number that does not match your vial — is not evidence about your material. It is evidence about someone else's.
3. Check the dates. A report should carry a test or analysis date consistent with the batch timeline. A COA from three years ago says nothing about a vial filled last month.
4. Confirm the product identity on the document. The product name, catalog number, and stated net amount should match your label.

For why this matters, see batch-specific COAs.

Step 2: Read identity, purity, and content as three different answers

The most common COA mistake is treating these three results as one number. They answer three different questions:

A vial can be ≥99% pure and still contain considerably less peptide than the label implies, because residual water and counterions (such as acetate) add mass that is not peptide. Conversely, an identity confirmation alone says nothing about purity. All three results together describe the material; any one alone is an incomplete picture.

What each test method demonstrates — and its limits

• HPLC purity measures the target peptide's share of peptide-related material (truncations, deletions, oxidation products). It does not measure non-peptide mass like water or salts, and it does not confirm identity. A purity number without a named method is not verifiable. See HPLC and peptide purity.
• LC-MS identity confirms the molecular weight of the main component. It does not quantify purity or content. See LC-MS.
• Endotoxin testing (LAL assay) detects bacterial endotoxin, a hazard for injectable-intended research material. A reported result is meaningful; the absence of the test is a gap. See endotoxin testing.
• Sterility testing (USP <71>) cultures a filtered sample in growth media for about 14 days to detect living microorganisms. It is a different test from endotoxin, and it samples only the tested portion. See sterility testing.
• Heavy metals (ICP-MS) checks elemental impurities such as lead, arsenic, cadmium, and mercury. See heavy metals.

An illustrative example (not a real report)

The lines below illustrate the kinds of fields a COA contains. This is not a genuine laboratory report:

Verifying the issuing laboratory and the report

• A named laboratory is stronger evidence than "in-house testing" with no lab identified.
• Accreditation (for example, ISO/IEC 17025) indicates the lab's methods are audited against a recognized standard. It describes the laboratory's systems, not any single report.
• Where a vendor publishes a searchable COA library, confirm your lot appears in it. Some vendors also allow you to contact the issuing laboratory with the batch number — either path is real verification.
• A report with no signatory, no letterhead, and no contact information is easy to forge and hard to check. For how forged documents circulate, see fake COAs are real.

What's missing, and questions worth asking

If a COA omits results, treat the omission as information rather than an accident. Questions worth asking a vendor:

• "Is this COA batch-specific, or typical values?"
• "Which method produced the purity number?"
• "Is there an identity result (LC-MS) for this lot?"
• "Is peptide content reported separately from purity?"
• "Are endotoxin and sterility results available for injectable-intended material?"
• "Can I verify this report with the issuing laboratory?"

Using a COA analyzer — and its limits

Our COA analyzer helps you organize what a report says: it checks which of six core testing categories (identity, purity, content, endotoxin, sterility, heavy metals) appear on the document and explains what each reported result means in plain language.

It is equally important to know what an analyzer cannot do. Interpreting reported information is not the same as authenticating a document. An analyzer cannot confirm that a report is genuine, that it was issued by the named laboratory, or that it describes your batch — and it cannot establish that a product is safe from an uploaded report alone. Authentication still runs through batch matching and laboratory verification as described above. See batch-specific COAs.

Red flags on a COA

• No batch number, or a batch number that doesn't match your vial
• No test date, or an undated template
• "Typical values" language — meaning the numbers are not from your batch
• Purity claimed with no method named
• No laboratory or signatory identified
• Perfect identical numbers across batches — real batches vary slightly

For how forged documents circulate, see our article fake COAs are real.

How to verify

Cross-check the batch number against the vial. If the seller publishes a COA library, confirm your lot appears in it. Where possible, prefer sellers whose COAs include identity testing and endotoxin results rather than purity alone.