How to Read a COA (Certificate of Analysis)

In the research peptide world, the Certificate of Analysis (COA) is the document that replaces the FDA. It's a lab report — usually one or two pages — that tells you what's actually in the vial.

A good vendor posts a COA for every batch. Learning to read it takes about ten minutes and will save you from most bad purchases.

What a COA is and isn't

A COA is a third-party lab test of a specific production batch of a peptide. It tells you:

• The peptide's identity (is this really BPC-157?)
• Its purity (how much of what's in the vial is actually the peptide?)
• Its mass (how many milligrams are in the vial?)

It does not tell you:

• Whether the peptide will work
• Whether the vial you received is actually from the batch tested
• Whether the peptide is safe for human use

That first bullet is the big one: a beautiful COA means the batch tested was good. It doesn't prove your specific vial came from that batch. This is why vendor reputation and community verification matter alongside the document itself.

The sections you'll actually read

A typical peptide COA has 4 or 5 sections. They usually appear in this order:

1. Header / identification

The top of the page lists:

• The peptide name and sequence
• The molecular formula and molecular weight
• The batch or lot number
• The date of analysis
• The lab that performed the testing

What to check:

• The batch number should match the batch number on your vial. Many vendors include this on the label or the packing slip.
• The testing lab should be a real third party (Janoshik Analytical, Benchmark Testing, NDC Analytical Solutions, and a handful of others are commonly seen). A COA from "our internal lab" is worth much less than one from an independent third party.
• The date should be reasonably recent. COAs more than a year old for your current vial are a warning sign — peptides degrade, and fresh testing matters.

2. Identity / mass spectrometry

This section confirms that the compound is what it claims to be.

• Method: Usually LC-MS (liquid chromatography / mass spectrometry) or MALDI-TOF.
• Expected mass: The theoretical molecular weight. For BPC-157 this is ~1419 Da. For semaglutide it's ~4114 Da. Pepperpedia lists these for most peptides.
• Found mass: What the lab actually measured. This should match the expected mass very closely (within a Dalton or so).

If "expected" and "found" don't match, the vial doesn't contain what the label says. Throw it out and change vendors.

3. Purity / HPLC

HPLC (high-performance liquid chromatography) is the main purity measurement.

You'll see a number like 97.3% or 98.6% or 99.1%. That number means: of the peptide-containing material in the sample, X% is the intended peptide. The rest is related peptide fragments, synthesis byproducts, or degradation products.

Rules of thumb:

• 98%+ is excellent.
• 95–97% is acceptable for most research peptides.
• Below 95% is a concern. Some complex peptides (long sequences, cyclic peptides) are harder to synthesize to high purity, but for standard compounds, sub-95% is a reason to ask questions.
• Below 90% — pass on it.

The HPLC section often includes a chart with a tall main peak and smaller side peaks. The smaller peaks are impurities. A clean COA has one obvious main peak and only small, consistent side peaks.

4. Mass / content

This tells you how much peptide is actually in the vial.

• A 5mg vial should test at approximately 5mg of peptide.
• Expect some small variation (±5% is typical).
• Underdosing is common at sketchy vendors. A vial labeled 10mg that tests at 6mg is effectively a 40% price increase — you're paying for mass you didn't get.

5. Additional tests (optional but welcome)

Higher-quality vendors also publish:

• Water content (Karl Fischer titration) — tells you how much residual water is in the lyophilized powder. Lower is better (under 10% is typical, under 5% is excellent).
• Acetate/TFA content — counter-ions used during synthesis. Not harmful at normal levels but affects the "net peptide" calculation.
• Endotoxin testing — important if you care about injection-site reactions. Often skipped in the research market.
• Sterility — rare on research COAs. Pharmaceutical-grade vials have this.

Red flags to watch for

• No batch number, no lab name, no date. A COA without these three things is decoration, not documentation.
• The COA is an image on the product page with no downloadable PDF. Honest vendors link to verifiable lab PDFs, often hosted on the testing lab's own domain.
• Same COA used for multiple batches or multiple products. Each batch should have its own fresh testing.
• Very round, suspiciously perfect numbers (100.0% purity, exact theoretical mass with zero deviation). Real lab results have minor noise.
• The vendor won't provide a COA on request. This is a deal-breaker.

The practical workflow

When you buy from a new vendor:

1. Download the COA for the specific batch of the product you're buying.
2. Check the peptide identity and mass against Pepperpedia or a reference.
3. Check the HPLC purity (95%+ for standard peptides).
4. Confirm the testing lab is independent and real.
5. Save the PDF. If something goes wrong later, you'll want the record.

Ten minutes of COA review beats any other single quality-control habit.

Where to go next

• Pepperpedia: Certificate of Analysis for the glossary entry.
• Pepperpedia Methods: Reading a COA for the technical deep-dive.
• Choosing a Supplier for how the COA fits into broader vendor evaluation.
• Pepperpedia: HPLC and Mass Spectrometry for the underlying methods.
• Beginner Questions forum for help reading a specific COA.