How to Read a Peptide Certificate of Analysis (COA)

If you've ever bought a research peptide, you've probably seen a Certificate of Analysis — or COA — included with your order. Maybe it was a PDF attached to an email, or a page on the vendor's website. Maybe you glanced at it and thought "looks legit" before moving on.

That's what most people do. But if you're spending real money on peptides, learning to actually read a COA is one of the best things you can do. It's the difference between trusting a company's marketing and verifying their product with science.

This guide will walk you through everything on a COA, what each section means, what the numbers should look like, and the red flags that tell you something's wrong.

---

What Is a COA?

A Certificate of Analysis is a document from a laboratory that shows the test results for a specific batch of a product. Think of it like a report card for your peptide. It tells you what's actually in the vial, how pure it is, and whether it passed quality checks.

Every reputable peptide vendor should provide a COA for every batch they sell. If a vendor doesn't offer COAs at all, that's your first red flag.

A proper COA comes from a third-party laboratory — meaning a lab that is not owned by or affiliated with the vendor selling the peptide. When a company tests its own products and writes its own COAs, there's an obvious conflict of interest. Third-party testing removes that bias.

---

The Key Sections of a COA

Most COAs follow a similar layout. Here's what you'll see and what it means.

Product Information

At the top, you'll find basic details:

• Peptide name — The name of the peptide (e.g., BPC-157, TB-500, Semaglutide)
• Batch or lot number — A unique identifier for this specific production run. This is important — it lets you match the COA to the exact product you received.
• Quantity — How much was tested (usually in milligrams)
• Molecular formula and molecular weight — The chemical identity of the peptide. This should match the known values for that peptide.
• Date of analysis — When the testing was done

What to check: Make sure the batch number on your COA matches the batch number on your product label. If they don't match, the COA might be from a completely different batch — or it could be fake.

Purity by HPLC

This is the most important number on the entire COA.

HPLC stands for High-Performance Liquid Chromatography. It's a technique that separates the different molecules in a sample so you can see what percentage is actually the peptide you want versus impurities.

The result is given as a percentage. For example, 98.5% purity means that 98.5% of the sample is the target peptide, and 1.5% is something else (leftover chemicals from manufacturing, degraded peptide, or other impurities).

What to look for:

• Above 98% — Excellent. This is pharmaceutical-grade territory.
• 95% to 98% — Good. Acceptable for most research purposes.
• 90% to 95% — Mediocre. You're getting more impurities than you'd want.
• Below 90% — Poor. Something went wrong in manufacturing. Avoid.

The HPLC section usually includes a chromatogram — a chart that looks like a series of peaks along a timeline. The main peak represents your peptide. It should be tall and dominant. Small secondary peaks are normal (minor impurities), but if you see multiple large peaks, that's a problem.

Red flag: A COA that says "98% purity" but doesn't include the actual chromatogram image. The chart is your proof. Without it, the number is just a claim.

Mass Spectrometry (Mass Spec)

Mass spectrometry confirms that the molecule in the vial is actually the peptide it's supposed to be. While HPLC tells you how pure the sample is, mass spec tells you what's in it.

The test measures the molecular weight of the molecules in the sample. The result is listed as an "observed" molecular weight, which should closely match the "theoretical" or expected molecular weight for that peptide.

Example: BPC-157 has a theoretical molecular weight of 1419.53 Da (daltons). If the mass spec result shows 1419.51 Da, that's a match. If it shows 1380.20 Da, that's a completely different molecule.

What to check: The observed mass should be within 1–2 daltons of the expected mass. A bigger difference means you might not have the right peptide at all.

Red flag: No mass spec data at all. Some cheap vendors skip this test entirely. Without it, you have no confirmation that the powder in your vial is what the label says.

Amino Acid Composition

Some COAs include amino acid analysis, which breaks down the individual amino acids in the peptide and compares them to the expected sequence. This is another way to confirm identity.

Each amino acid should appear in the correct ratio. For example, if the peptide sequence includes two glycine residues and one leucine, the analysis should show a 2:1 ratio.

This test isn't always included, especially for shorter peptides where mass spec is sufficient. But for longer or more complex peptides, it adds an extra layer of verification.

Endotoxin Testing (LAL Test)

Endotoxins are toxins released by certain bacteria. If peptides are manufactured in unclean conditions, bacterial contamination can introduce endotoxins into the product.

The LAL (Limulus Amebocyte Lysate) test measures endotoxin levels. Results are given in EU/mg (Endotoxin Units per milligram).

What to look for:

• Below 0.5 EU/mg — Good. This is well within safe research limits.
• Below 5 EU/mg — Acceptable for most research applications.
• Above 5 EU/mg — Concerning. High endotoxin levels can cause inflammation and other reactions.

Red flag: No endotoxin testing at all. This is more common than you'd think, especially with budget vendors. Endotoxin contamination is invisible — you can't see it, smell it, or taste it. The only way to know is to test.

Appearance and Solubility

These are basic physical observations:

• Appearance — Usually described as "white to off-white lyophilized powder." If the powder is yellow, brown, or clumpy, something's wrong.
• Solubility — Notes on how well the peptide dissolves in common solvents like bacteriostatic water or sterile water. Proper peptides should dissolve clearly without particles floating around.

Water Content (Karl Fischer Test)

Lyophilized (freeze-dried) peptides should have very low moisture content — typically under 5%. Higher moisture means the drying process wasn't done well, and the peptide may degrade faster during storage.

---

Red Flags That Should Worry You

Here's a quick checklist of warning signs:

1. No batch number — Without this, you can't verify that the COA matches your product.
2. No chromatogram image — Just a purity percentage with no supporting data.
3. Purity below 95% — Unless it's a known hard-to-synthesize peptide, this suggests low-quality manufacturing.
4. Mass spec mismatch — The observed molecular weight doesn't match the expected value.
5. No endotoxin data — The vendor didn't bother testing for bacterial contamination.
6. The lab name is missing or vague — A real COA names the specific laboratory that performed the testing.
7. Every batch has identical results — If a vendor posts the same COA for every batch, they might be reusing one document. Real testing produces slightly different numbers each time.
8. The COA is a low-quality scan — Blurry text, cropped sections, or obviously edited documents are red flags.
9. Testing date is very old — A COA from two years ago doesn't tell you much about the peptide sitting in your fridge today.

---

How to Verify a COA

Reading a COA is step one. Verifying it is step two.

Contact the Lab Directly

Most legitimate COAs include the name and contact information of the testing laboratory. You can reach out to them and ask:

• "Did you test batch number [X] for [vendor name]?"
• "Can you confirm these results?"

Reputable labs like Janssen Labs, Colmaric Analyticals, or Intertek will confirm or deny. If the vendor claims testing from a lab that has no record of them, that's your answer.

Cross-Reference Known Values

Look up the expected molecular weight, amino acid sequence, and typical purity ranges for the peptide you bought. Scientific databases like PubChem, UniProt, or even the vendor's own product spec sheet can give you reference values. If the COA numbers don't match published data, something's off.

Check the Lab's Accreditation

Testing labs should be ISO 17025 accredited or follow GMP (Good Manufacturing Practice) standards. You can usually verify accreditation on the lab's website or through accreditation body databases. An accredited lab follows standardized procedures that make their results more reliable.

Compare Across Batches

If you've bought from the same vendor multiple times, compare COAs across batches. The numbers should be similar but not identical. Real analytical testing always produces small variations. If every single COA shows exactly 99.1% purity and exactly the same molecular weight down to the hundredth decimal, that's suspicious.

---

Why This Matters

A COA isn't just paperwork. It's the only objective evidence you have about what's in your vial.

The peptide market — especially the research and gray-market space — has minimal oversight. There's no FDA inspector checking every batch. There's no standard enforcement body making sure vendors ship what they claim. The COA is the closest thing you get to accountability.

Learning to read one takes about ten minutes. But it can save you from wasting money on underdosed, contaminated, or fake products. It can also protect your health if you're using peptides in any capacity.

The vendors who invest in proper third-party testing and publish complete, verifiable COAs are the ones who take their product seriously. And those are the vendors worth buying from.

---

Quick Reference Checklist

Before you accept a COA as legit, make sure it has:

• ✅ Specific batch/lot number matching your product
• ✅ HPLC purity ≥ 95% with chromatogram image
• ✅ Mass spectrometry data matching expected molecular weight
• ✅ Endotoxin testing results (below 5 EU/mg)
• ✅ Named third-party laboratory with contact info
• ✅ Recent testing date
• ✅ Physical appearance description
• ✅ Unique results (not copy-pasted from another batch)

If a COA is missing more than one or two of these, ask the vendor for a complete version. If they can't provide one, consider shopping elsewhere. Your peptides are only as good as the proof behind them.