How to Read a COA: The Non-Scientist's Guide

You're about to drop $150 on a vial of peptides. The vendor sends you a "Certificate of Analysis" as proof it's legit. You open the PDF and see this:

"HPLC-DAD analysis indicates 98.43% purity (area %). Retention time: 4.17 min. Mobile phase: acetonitrile/water gradient. Mass spec confirmed m/z 3297.8 [M+H]+. Endotoxin <0.5 EU/mg."

...and you have absolutely no idea if that's good, bad, or completely made up.

You're not alone. Most people buying research peptides can't read a COA. That's a problem, because knowing how to spot a real vs. fake testing report is the difference between getting quality compounds and getting ripped off.

This guide translates COA jargon into plain English. By the end, you'll know exactly what to look for—and what red flags mean "run away."

What Is a COA, Actually?

A Certificate of Analysis (COA) is a document from an independent testing lab that verifies what's in your vial. Think of it like a nutrition label, but for peptides—except way more technical and harder to fake (if you know what to look for).

A legitimate COA tells you:

• Purity — how much of the vial is the peptide you paid for vs. junk
• Identity — confirmation it's actually the compound it claims to be
• Safety — whether it's contaminated with bacteria or toxins

Without a COA, you're trusting a random internet vendor with zero accountability. With a COA, you at least have evidence—if you know how to read it.

Section 1: The Header (Who, What, When)

The top of every real COA includes basic info. This is where you catch most fakes.

Lab Name & Accreditation

The lab doing the testing should be listed at the top with their accreditation number. In peptide testing, the gold standard is ISO/IEC 17025 accreditation—it means the lab has been audited and verified by an independent third party.

Common legitimate labs:

• Janoshik Analytical (Czech Republic) — most common in the research peptide world
• Chromate (USA)
• LabCorp or Quest Diagnostics (for pharmaceutical-grade work)

Batch Number & Test Date

Every legitimate COA is tied to a specific batch of peptides. The batch number on the COA should match the batch number on your vial.

Why this matters: A vendor showing you a single COA from 2023 for products they're selling in 2026 is playing games. Peptides degrade. Testing should be recent and batch-specific.

Product Name & CAS Number

The COA should clearly state what peptide was tested. Look for the CAS number—a unique chemical identifier that confirms they tested the right compound.

Example: Semaglutide's CAS number is 910463-68-2. If the COA says "Semaglutide" but lists a different CAS number (or no CAS at all), something's wrong.

Section 2: Purity Testing (The Part Everyone Cares About)

This is the main event. Purity tells you how much of the vial is the actual peptide vs. leftover synthesis byproducts, water, or other junk.

HPLC Purity (Area %)

Most COAs report purity as a percentage determined by HPLC (High-Performance Liquid Chromatography). This is the industry standard method for peptide testing.

Here's how it works in one sentence: The lab dissolves your peptide in liquid, runs it through a column, and measures how much of the sample is the target peptide vs. impurities.

What the numbers mean:

• 98%+ — Excellent. This is what you want.
• 95-98% — Good. Acceptable for research use.
• 90-95% — Mediocre. You're paying for filler.
• Below 90% — Garbage. Don't buy it.

The HPLC Chromatogram (The Graph)

A real HPLC test includes a graph called a chromatogram. It looks like a line with peaks.

What you're looking for:

• One big peak — That's your peptide.
• Small peaks before or after — Those are impurities.

The bigger the main peak relative to the small ones, the higher the purity. If the chromatogram looks messy with multiple large peaks, the sample is contaminated.

Section 3: Identity Confirmation (Mass Spectrometry)

Purity tells you how much peptide is in the vial. Identity confirmation tells you it's the right peptide.

This is done with mass spectrometry (MS). The lab measures the molecular weight of your compound and compares it to the expected value.

How to Read It

You'll see something like this:

"Observed m/z: 3297.8 [M+H]+
Expected m/z: 3297.7"

Translation: The measured molecular weight (3297.8) matches the theoretical weight of the peptide (3297.7). It's the real thing.

What you're checking: The "observed" value should be within 1-2 units of the "expected" value. If it's way off, you've been sent the wrong peptide (or a fake).

Section 4: Contamination Testing (The Safety Part)

Even if your peptide is pure and correctly identified, it could still be contaminated with bacteria or endotoxins (toxins from bacterial cell walls). This section tells you if it's safe.

Bacterial Endotoxin Test

You'll see a line like: "Endotoxin: <0.5 EU/mg"

EU stands for Endotoxin Units. For research peptides, you want this number below 1 EU/mg. Below 0.5 is even better.

Why this matters: Endotoxins cause inflammation and immune responses. If you're doing in vivo research (animal studies), high endotoxin levels will skew your results.

For context, the FDA limit for injectable drugs is 5 EU/kg of body weight. A 70kg human would tolerate 350 EU total dose. If your 5mg peptide vial has 2.5 EU (<0.5 EU/mg), you're well within safe limits for research use.

Sterility Testing

Some COAs include sterility tests (bacterial culture tests). You'll see: "Sterile: Pass" or "No growth detected."

This confirms there are no living bacteria in the sample. Not all vendors test for this (it's expensive), but premium suppliers include it.

Section 5: What Legitimate Labs Include

Here's a checklist of what a real COA from a real lab should have:

• ✅ Lab name with ISO 17025 accreditation number
• ✅ Test date (recent, ideally within 6 months)
• ✅ Batch number matching your vial
• ✅ Product name + CAS number
• ✅ HPLC purity (area %) with chromatogram
• ✅ Mass spec identity confirmation
• ✅ Endotoxin test results
• ✅ Contact info for the lab (not just the vendor)

If any of these are missing, ask the vendor why. If they dodge the question, walk away.

Common Tricks Sketchy Vendors Use

Now that you know what a real COA looks like, here are the tricks bad vendors use to fool people:

1. Generic COAs with No Batch Numbers

They show you a COA with no batch number or a date from two years ago. When you ask for current testing, they say "it's the same batch." (It's not.)

2. Photoshopped Lab Reports

They take a real Janoshik report for a different peptide, change the product name in Photoshop, and hope you don't notice the CAS number doesn't match.

How to catch this: Cross-reference the report ID with the lab's database. Janoshik publishes all test results publicly with searchable IDs.

3. In-House "Testing"

They claim they "test in-house" instead of using a third-party lab. Translation: they're making it up.

Rule of thumb: If the testing isn't done by an independent, accredited lab, it's worthless.

4. Weight % Instead of Area %

They report purity as "98% by weight" instead of "98% by area." This inflates the number because it includes water content and counter-ions (salts used in synthesis).

A peptide that's 98% by weight might only be 90% by area (the real purity measure).

The Bottom Line

Reading a COA isn't rocket science, but vendors count on you not knowing how.

If you remember nothing else from this guide, remember this:

• Demand batch-specific testing from an accredited third-party lab.
• Look for HPLC purity (area %) above 95%.
• Verify the mass spec confirms the correct molecular weight.
• Check that endotoxin levels are below 1 EU/mg.

If a vendor won't provide this—or if the COA looks sketchy—buy elsewhere. There are legitimate suppliers who do this right. Don't settle for less.