What Is a Certificate of Analysis (COA)?

If a supplier hands you a document labeled "Certificate of Analysis," do you know what you're actually looking at? This guide breaks down what a COA is, what a good one looks like, the red flags to watch for, and how to confirm the documentation is genuine.

What is a Certificate of Analysis?

A Certificate of Analysis is a lab document reporting the results of analytical testing performed on a batch of compound. For research peptides, a COA typically confirms:

Identity — that the compound in the vial is actually the compound on the label
Purity — the percentage of the active compound relative to impurities
Absence of contaminants — residual solvents, heavy metals, bacterial endotoxins (depending on the testing scope)

The COA is batch-specific. Each production run gets its own document with its own lot number. When you receive a vial, the lot number on the label should match the lot number on the COA.

The critical difference: third-party vs. in-house COAs

This is where most discussions of peptide COAs become vague. There are two fundamentally different types.

In-house COA

The supplier tests their own product in their own facility and produces the document internally. This is better than no documentation — a legitimate supplier who cares about quality will run real testing and report accurate results. But it's self-reported: no independent party has verified it.

Third-party COA

An accredited, independent laboratory — one with no financial relationship with the supplier — tests the compound and issues the report. The lab's name, accreditation, and contact information appear on the document, and you can, in principle, contact that lab to confirm the report is genuine.

The gold standard

A third-party COA can't be fabricated without forging an entire laboratory's identity. An in-house COA can be falsified by anyone with design software. So when you see "COA available," your first question should be: which lab produced it?

What a good COA looks like

A high-quality COA for a research peptide should include all of the following:

1. Testing laboratory information

Full lab name and address
Accreditation body (ISO/IEC 17025 is the relevant standard for testing labs)
Lab contact information (phone, email, or both)
Analyst signature or lab-director certification

2. Sample identification

Compound name, matching the vial label exactly
Lot or batch number
Sample receipt date and test date
Client / supplier name (confirms who submitted the sample)

3. Test methods and results

HPLC — the standard for purity analysis
MS (mass spectrometry) or NMR — for identity confirmation
Purity percentage with a specification, e.g. "Purity: 99.1% — Spec: ≥98%"
A clear pass/fail determination

4. Scope of testing

More comprehensive COAs also cover heavy metals, residual solvents, and microbial/endotoxin testing
At minimum, a credible COA confirms identity and purity

What 98% purity means

Research-grade peptides are generally considered acceptable at ≥98% purity. At that level, 98% of the content is your target compound and 2% is other material — most of which is typically water, counterions, and synthesis byproducts, not toxic contaminants. Higher is better, but 98% is the standard baseline.

Red flags: when a COA isn't actually a COA

No lab name, or a generic/unverifiable one. "XYZ Internal Lab" with no address, accreditation number, or independent contact is an in-house document at best, fabricated at worst.
Test date more than 12–18 months old. An old COA may not reflect the current batch. Fresh stock should have recent testing.
Lot number mismatch. If the lot number on your vial doesn't match the COA, the document may not apply to your batch.
Suspiciously round purity numbers. Genuine HPLC results come back specific — 98.3%, 99.1%, 97.8%. Exactly "100%" or "99.0%" on every compound is worth scrutiny.
No test method listed. Any legitimate lab specifies the technique used. Purity with no named method has no credibility.
COA not downloadable or zoomable. If you can't inspect the lab information, you can't verify it.

Let Pep Trust do the cross-checking

Upload a COA and get an authenticity and completeness score in plain language — which sections are present, whether the molecular weight matches, and whether the lab is traceable.

Verify a COA — free

How to verify a COA

For in-house COAs, you largely can't verify them independently — treat them as the supplier's self-assessment. For third-party COAs, verification is possible:

Identify the lab. Search the name and confirm it's a real, operating analytical laboratory.
Check for accreditation. Look for ISO/IEC 17025 (or NVLAP/A2LA in a US context). Many accrediting bodies publish searchable directories.
Match the lot number. Confirm the COA's lot number matches your vial or order.
Check the test date. It should fall within the last 12–18 months for active stock.
Look up the relationship. For well-known labs, you can sometimes confirm testing relationships through client lists or public announcements.

The practical takeaway

If purity matters to you — and it should — the COA question is simple. Does the supplier provide a COA? Is it from an independent third-party lab? Can you verify the lab is real and accredited? Does the lot number match your order?

Suppliers who pass all four are doing the most to give you confidence in what you're receiving. Suppliers who pass only the first are operating at the basic standard the market accepts — but that falls short of what serious documentation looks like.

Research use only. This article is for scientific and educational purposes and is not medical, dosing, or investment advice. Research peptides are not approved for human or veterinary use.

What Is a Certificate of Analysis (COA) — and Why It Matters